What Is Bleeder Resistor: 11 Important Facts You Should Know

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What is bleed resistor ?

Bleeder Resistor:

This is a standard high-value resistor (connected in parallel with the filter capacitor) used to discharge the capacitor in a filter circuit and primary purpose of using a bleeder resistor in any circuit is safety.

The discharging of the capacitor is very important because even if we turn off the power supply, the charged capacitor can give an electric shock. So it is essential to add a bleed resistor to avoid any mishap.

The function of bleeder resistor:

Let us assume a rectifier with a capacitor filter connected to a power supply. Now, there can be no load present in the circuit, whenever the diode is forward-biased, the capacitor gets charged. As a result, the capacitor produces some voltage across it.

When the diode is reverse biased, the capacitor discharged by a resistor. If the load resistor is not connected, the voltage will be there across the terminals. Now, if we turn off the AC supply, the capacitor still holds some charge. So, if someone touches the terminals, he may get an electric shock. If we can create a discharge path for the capacitor, then We can solve this problem.

Therefore, we connect a highly valued resistor in parallel with the capacitor. This resistor provides a discharge channel for the capacitor. Therefore, it is known as a bleeder resistor.

Bleeder resistor in filter circuit:

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Filter Circuit

As we have seen, filter circuits make use of bleeder resistors to ensure safety. Let us think of a simple circuit where a capacitor is attached to the main circuitry. Now once the power supply is ON, the capacitor gets charged. After some time, it reaches the peak value and then starts discharging.

The capacitor remain charged for some seconds after the power supply is OFF. If the capacitor is of very high value, severe problems can happen. First, the capacitor may give a substantial electric shock. Second, if a resistor is connected in parallel, the capacitor gets discharged through this resistor.

How to test a start capacitor with a bleed resistor?

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Capacitors in the circuit

Bleed resistor for start capacitor

A capacitor is an energy-storing device. Engineers use this to perform various operations in an electric circuit. First, the capacitor is tested to determine if it is working correctly or not.

When a capacitor is placed in a circuit where the current is flowing, an electric charge builds up on the capacitor plates and after some time, the capacitor accepts no charge, and it means that the capacitor is totally charged. If the circuit requires a charge, the capacitor discharges until the entire charge returns to the circuit.

Following are the steps for testing a start capacitor with a bleed resistor:

  • We short the capacitor terminals using a metal contact.
  • ‌Digital multimeter readings are taken.
  • ‌The power supply is turned on, and we measure how much time the capacitor takes to charge 63.2% of the supply voltage.
  • ‌We calculate the time constant of the capacitor and further determine the capacitance value.

If the voltage rating is the identical or more than the older one, we can say that the start capacitor is working fine.

The bleed resistor on run capacitor:

A run capacitor is a device that optimizes a motor’s performance by adjusting the current and the phase shift. The main difference between a run capacitor and a start capacitor is the first one works continuously, and the second one works in cycles like a switch. As there’s no need for the switch in a run capacitor, the bleed resistor is also unnecessary.

Bleeder resistor design:

A bleeder resistor works when the load resistor is disconnected.

A bleed resistor functions best when it is situated at the 1st capacitor after rectifier, doesn’t draw much current, but it can still cause a volt-drops if connected in series. That’s why the components are connected in parallel.

Bleeder resistor circuit:

Bleed resistor circuit
Bleed resistor circuit

The above rectifier circuit initially consists of an AC power supply, a heavy-duty transformer, two diodes D1 and D2, filter choke L, and filter capacitor C. This capacitor is a large electrolytic capacitor. Therefore, the voltage charging up the capacitor would be very high. However, when we switch the power supply down, a significant voltage still stays for quite some time. So a resistor Rb is connected, which helps in discharging the capacitor.

How to calculate Bleeder resistor value ?

Bleed resistor formula 

The mathematical formula to find bleeder resistance requirement is

Rb = – t/C x ln Vt/Vi

Where C is the capacitance value.

  • t is the time needed for the capacitor to discharge via the bleed resistor.
  • Vt is the voltage up to which the capacitor can be discharged
  • Vi is the initial voltage on the capacitor
  • We cannot exactly specify the value of Vt. However, any low value of Vt serves the purpose.

Treble bleed resistor value

Treble bleed circuits are typically used in guitars. These are standard high-pass circuits that consist of a capacitor soldered to the center and the outside lugs of the volume control. When resistors are used in the treble bleed circuit, they attenuate the high frequencies so that the signal frequency remains balanced. Though there’s no specific information available about the resistor value, it ranges from 120 Kohm to 150 Kohm.

Treble bleed without the resistor

Treble bleed mods are used in some guitars. A resistor might be wired in parallel with a treble bleed or might not be used at all. They can have slightly different effects on the control. However, the tones appear to be the same with or with out the resistor.

Start capacitor bleed down resistor

The bleed-down resistor is the resistor used with the start capacitor. Here “bleed” means to pass. The bleed-down resistor is used to pass off the residual voltage in the start capacitor after removing it from the motor circuit. Though a bleed-down resistor is a safe way, there are other ways to reduce the residual voltage. The resistance value should be somewhere between 10k ohms to 20k Ohms and resistors are generally crimped to the terminals of the start capacitor.

led bleed resistor:

One of the most challenging jobs in LEDs is to improve the dimming of LED lamps in TRIAC dimmers. As these do not have a resistive load, TRIACs intermittently turn off and on and create the flickering effect. This effect degrades the dimming.

To cope up with this issue, LED designers are now introducing bleeding circuits. A small bleed resistor, when used with a capacitor, is called the bleeding circuit. In the LEDs, the bleed resistor is only turned on when needed. Therefore, a trade-off is established, power consumption is lowered, and greater efficiency is attained.

Static bleed resistor:

The bleed resistors are used in Kite antennas for a static build-up. It reduces the voltage observed across the front end of the radio.

Function of bleeder resistor in dc power supply

There are three primary functions of a bleeder resistor.

  • The primary function of a bleed resistor is to provide safety. The capacitor of the filter starts charging when we connect the main supply with the circuit. The capacitor reaches its peak and gradually discharges. Even when the discharging process ends, some excess charge remains in the circuit, and it can give an electric shock to anybody touching the circuit. A bleed resistor connects in parallel help to pass the extra charge thru it.
  • The bleed resistor may act as a voltage divider too. If the equipment is supposed to generate 2 or multiple volt-supplies, the device can be tapped, and the bleed resistor can act as a substitute for the series circuit.
  • Another important use of the bleed resistor is voltage regulation. Mathematically, voltage regulation is the ratio of the diff in between full load and no-load voltage with the full load voltage. As the difference increases, the voltage regulation improves. To attain this, we need to join the bleed resistor in parallel to the filter circuitry and the load resistor, volt-drop occurs in the bleed resistor, this can acts as a voltage regulator too.

SSR bleeder resistor:

SSR refers to the solid-state relays. A solid-state relay is a four-layer switching device that turns OFF and ON if any external voltage is applied across the control terminals.

The leakage current of the SSR circuit on the input side may cause a reset failure. Insertion of a bleed resistor can help prevent this.

 The bleeder resistance value must be set so that the SSR input voltage is a maximum of 0.5 V. when the Relay is OFF.

Reset failure may occur due to solidstate relay leakage current and If this current is higher than the load release current, the solidstate relays may face resetting failure and to increase the Solid-state relay switching current, this resister are adjoined in parallel.

Bleeder resistor tube amp.

The bleeder resistor is not a typical electronic device that is used in everyday gadgets. However, some special equipment like musical instruments, amplifiers contain bleeder circuits. The tube amplifier is such a device. The bleed resistor connected in parallel with the amplifier circuitry easily discharges high voltage capacitors.

ESD bleeder resistor

ESD stands for electrostatic discharge. This discharge might cause damage if not done correctly. So the testing of ESD must be done even it is time-consuming one. Here, the device requires 470 Kohm resistors connected to the ground. The presence of a bleed resistor drastically changes the test results. But the bleeder resistor is needed so that during testing, nobody gets an electric shock.

The most common value for a bleeder resistor

The ratings of the bleeder resistor varies in every circuitry. For example, for a start capacitor AC motor, the value ranges from 10k ohm to 20k ohm. For some other filter circuits, the value can even be more than 200k ohm.

FAQs

What is the bleeder resistor used for?

A bleeder resistor is majorly used in filter circuits to add to the safety and prevent electric shock.

How do I choose a bleeder resistor?

There is always a trade-off between the speed of the bleeder and the total power waste and low values of bleed resistors give a faster time for discharging, but they will give more power loss. We may choose the value with the help of this equation:

Vt = Vie-t/RbC

Where Vt is the instantaneous voltage across the capacitor

Rb is the bleeder resistance

Vi is the initial voltage

t is the instantaneous time period, and C is the capacitance value.

What is a bleed down resistor?

A bleed down resistor is seen in a motor circuit where there’s a built-in start capacitor. The capacitor usually operates for very short instances while the motor is coming up to speed,  if the motor speed up, the capacitor is not required after speeded up. So there should be a switch or voltage sensing device to pull the capacitor out of the circuit. But even after the capacitor is pulled out, for a few seconds, the voltage remains high. It may cause hazards. Therefore a resistor is connected to bleed down the voltage. It is known as a bleed down resistor.

What is bleeder resistance?

This is the resistive value of the bleed resistor in ohm.

How do I select the value of the bleeder resistor to discharge a capacitor at the DC bus automotive inverter application?

The bleeder resistor value should be very high if we want to lower the power consumption when the inverter is kept on. Similarly, the value should be such that the capacitor gets discharged fast.

Why does a DC/DC converter have a bleeder resistor at its output?

The DC/DC converters regulate substantial output capacitance and low load. So, after the device is turned off, there can be a considerable amount of charge left. This charge may take up to several minutes to be discharged and may give a shock to anybody working with it. Therefore, a resistor is attached to the output to fasten this discharging process.

Why do some capacitors have resistors attached to them?

Sometimes capacitors with high value contain resistors so that the stored charge gets drained fast after the power supply is turned off. This resistor provides a discharge channel for the capacitor. Therefore, it is known as a bleeder resistor.

How to use a discharge resistor?

The discharge resistor must be kept in parallel with the circuit so that it can drain the excess charge.

The discharging of the capacitor is very important because even if we turn off the power supply, the charged capacitor can give an electric shock. So it is essential to add a bleed resistor to avoid any mishap.

How do an X rated capacitor and a bleed resistor reduce the voltage in a transformerless power supply?

X rated capacitors have high voltage ratings that can directly be used with AC mains in series. Here the capacitor is used as a voltage divider. Along with the capacitor, the circuit contains a Zener diode and a rectifier with the bleed resistor. The capacitive reactance helps in reducing the voltage.

Why do you need a bleed resistor on the start capacitor?

The start capacitors make use of a bleed resistor to accomplish any task safely after the power supply is turned off.

The function of the bleeder resistor is-

  1. To keep the circuit safe from hazards
  2. To draw high current
  3. To optimize the efficiency of the rectifier
  4. All of the above

Answer: The bleed resistor provides a channel for the capacitor to discharge the remaining charge. Thus it saves the circuit from undesirable accidents.

Which of the following statement(s) is/are true about the bleeder resistors-

  1. The bleeder resistors are connected in parallel with the main circuit
  2. A bleeder resistor prevents the amplifiers from being over-driven
  3. The bleeder resistors can act as voltage regulators
  4. None of the above

Answer: 1 and 3 are correct option. The bleeder resistors are connected in parallel so that they can quickly discharge the capacitor. These can also work as voltage regulators by creating differences between load voltages.

The function of a bleeder resistor in a power supply is

a. To amplify the voltage

b. Discharge the stored charge on the capacitor

c. To increase the output current

d. All of these

Answer: The bleed resistor is used to discharge the capacitor as soon as possible so that no one gets an electric shock while touching the circuit and nothing to do with the current.

How to Calculate bleeder resistor power supply ?

bleed resistor power supply

Let us take a filter circuit connected to an AC supply voltage and has a capacitor with a capacitance value of 2 micro Farad. The initial voltage Vi is 1000 volt, and Vt is 10 volt. The discharging time is 5 seconds, then using the formula, we can calculate the value of the bleed resistor needed to discharge the capacitor.

We know, Rb = -t/[C x ln(Vt/Vi)]

Therefore, Rb = -5/[2 x 10-6 x ln(10/1000)] = 542,888 ohm

Cam and Follower: Definition, Types, Working Principle, Advantages, Applications

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Table of Content

Cam and follower

Cam and follower is a mechanism used to get the desired motion such as reciprocating or translational from an available input, usually rotational.

Cam and follower with different size and shape are available in the market.

The elements of the mechanism are;

  • Cam
  • Follower

Diagram of cam and follower

Cam and follower

What is a Cam?

Cam is the driving component in the mechanism, making sure that the follower follows the desired motion.

Hence, the profile and size of the cam are significant in a cam and follower mechanism.

While designing the mechanism, the main concern goes to getting the appropriate profile of the cam.

What is a follower?

The component which gives the desired motion in the mechanism is the follower. The motion of the follower is the output in the cam follower mechanism.

Generally, followers are having two distinct types of motions, oscillating and reciprocating. The followers are designed in such a way that, it always touches the cam during the cam operation.

As the follower moves over the cam, there is friction resistance and side thrust acting. The friction resistance leads to the wear failure of the cam follower mechanism.

Classification of cam and follower | Different types of cam and follower

There are different types of cams and followers available according to the applications.

Those are discussed below;

Types of Cams

The cams can be classified as follows;

Cam Working Low 2

Types of cams : based on the shape

  • Plate or disk cam

It is the most commonly used cam. It is cut from a metal disk or plate to a pre-planned shape according to the requirement.

Many important cam parameters can be explained using the plate cam, like the base circle, pressure angle, pitch point, etc.

.

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  • Cylindrical cam

The cam is of cylindrical shape. A groove is cut on the surface of the cylinder and follower moves inside the groove. The cylinder rotates, and the follower oscillates accordingly.

Cylondrical Cam Low 3
  • Wedge cam

The figure shows a wedge cam. Wedge cams have a wedge of specified shape that reciprocates and leads to reciprocation or oscillation of the follower.

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  • Spherical cam

A spherical cam is similar to a cylindrical cam; the only difference is groove is cut on a sphere instead of a cylinder.

  • Globoid cam

Globoid cam is also similar to cylindrical cam; the only difference is grove is cut on a globoid shape.

Globoidal Cam Low 3
  • Conjugate or dual cam

The conjugate cam consists of two-disc cams that are bolted together. This type is used for very quiet operations.

Types of cams : based on follower movement

The follower movement can be classified as,

  • Dwell – No movement to the follower.
  • Rise or Ascend – The follower moves upward.
  • Return or Descent – The follower moves downward.

The cam profile controls the length and amount of ascend, descend or dwell in a cam follower mechanism. Hence, according to the follower movement, cams can be classified.

By proper design of cam profile, any combination dwell, rise or return can achieve. In each cycle, the follower comebacks to the initial state. Hence, if there is a ascend, then the equal amount of descent will be there in the cam profile automatically.

Some combinations are,

  • Rise, Dwell, Return cam
  • Rise, Return, Rise cam
  • Dwell, Rise, Dwell, Return, Dwell cam

Types of cams : based on the type of constraint

  • Spring-loaded: The contact between cam and follower is enabled using a pre-loaded spring.
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  • Positive drive: Providing groove as shown in cylindrical cam is an example of a positive drive cam. Here, the follower motion is constrained due to the presence of groove.
  • Gravity cam: The gravity force helps to keep the contact between cam and follower. The follower weight should be sufficient in order to get constant contact.
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Types of Followers

The followers can be classified as follows;

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Types of Followers : Based on the shape of the follower

  • Knife edged follower

An example of a knife-edge follower is given in the figure. It is having a sharp edge, i.e., knife edge, making contact with the cam.

We can expect a higher frictional resistance and wear for these types of cams. And the system has considerable side thrust also. Due to these limitations, it is not commonly used.

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  • Roller follower

In this follower, the pointed edge is replaced with a roller that freely rotates about its axis. Here, the frictional resistance and wear are reduced. However, the side thrust is not eliminated.

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  • Flat-faced follower

It is also called a Mushroom follower. The point contact in the knife-edge follower is replaced with a flat plate, as shown in the figure. Here, the frictional resistance is not reduced; however, a considerable decrease in side thrust can be achieved.

The cam profile should have a convex shape for this type of follower; otherwise, the follower and cam get stuck in the concave profile of the cam.

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  • Spherical faced follower

This is similar to flat-faced follower; the difference is that the contacting profile has the shape of a hemisphere; hence the frictional resistance also reduces.

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Types of Followers : Based on the motion

  • Oscillating follower

The follower oscillates in this type of cam follower mechanism. An example is given in the figure.

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  • Reciprocating follower

The follower reciprocates in this type of cam follower mechanism. An example is given in the figure.

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Types of Followers : Based on the path of the follower

  • Radial or in-line follower

In this type of followers, the cam center and line of action of the follower are in same line as shown in figure.

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  • Offset follower or Eccintric cam follower mechanism

In this type of followers, extended line of action of follower and cam center does not lie in the same line. The side thrust is reduced if we are using an offset follower.

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The Terminology of a Cam

We already discussed the importance of a cam profile.

Now we will be looking into some important terminology of the cam.

The figure shows a cam with a roller follower, indicating all the terms we are about to discuss.

Cam Terminology Low 2

The roller at the different positions over the cam is shown, assuming the cam remains stationary and the roller travel along with the cam profile.

  • Base Circle 

It is the smallest circle drawn with center on the cam center and touches the cam profile.

  • Trace points

These are the arbitrary points around the cam profile, through which the center of the follower moves.

In the case of roller follower, trace points are obtained by adding the radius of the roller from the cam profile, as shown in the figure.

For knife-edge followers, the trace points are on the cam profile itself.

  • Pitch curve

If we join all the trace point we get the pitch curve.

  • Prime circle

It is the smallest circle drawn with center on the cam center and touches the pitch curve.

  • Pressure angle

Pressure angle is defined in every point in pitch curve.

It is the angle between direction of the follower movement and the normal to the pitch curve.

Higher the steepness in the cam profile, the higher the pressure angle.

Higher pressure angle is not preferred as it increases the force required to lift the follower.

  • Pitch point

It is a point in the pitch curve where the pressure angle is maximum.

  • Pitch circle

Circle with center on cam center and passes through the pitch point.

Working mechanism of cam and follower

The figure shows the cam and follower mechanism at different positions.

Cam Working 2

In the given figure, the cam rotates in an anticlockwise direction.

Initially, for some duration, the follower moves upward. The upward movement is known as the ascend or rise period (between (a) and (b)).

After that, the follower stays in the same position for some rotation of cam (between (b) and (c)).

Hereafter, the follower moves downward (between (c) and (d)), known as descend or return. At the end of the return, the follower reaches its initial position and remains stationary until the next cycle starts (between (d) and (e)).

The cycle keeps on repeating. Here, we got the reciprocating motion for the follower from the rotational movement of the cam.

The motion of the follower can be categorized as rise-dwell-return-dwell.

We can change the motion of the follower by appropriately designing the cam profile.

Imagine the follower motion for figure given below,

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Forces acting in a cam and follower mechanism

There are mainly two forces acting in cam follower mechanism, normal force and frictional force.

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The direction of normal force and frictional force is shown in the figure. The normal force acts normal to the cam profile, and the frictional force acts tangential to the cam profile.

The normal force can split into two components; horizontal and vertical.

The equation for horizontal and vertical force are given below,

F_v = F_ncostheta

F_h = F_nsintheta

The vertical force is helping to lift the follower. The horizontal force is an unnecessary force, which gives a side thrust to the follower.

The angel θ is the pressure angle.

The above analysis is carried out only for normal force. The frictional force also can be analysed similarly by splitting it into horizontal and vertical components.

It can be observed that the friction force increases the side thrust and decrease the net lift force.

Side thrust in cam and follower

As explained above, the side thrust is an unnecessary force that should be reduced for the smooth operation of the cam and follower mechanism.

One component of normal force and frictional force is contributing to the side thrust.

The side thrust can be reduced by,

  • Using a flat face follower
  • Using offset cam follower mechanism.
  • Reducing the pressure angle.
  • Reducing the friction

Significance of pressure angle in cam and follower

From the above analysis, we can see that the increase in pressure angle leads to a decrease in the lift force and an increase in the thrust force. The lift force must be sufficient to overcome the spring force or gravitational force in the cam follower mechanism. Hence, if the pressure angle is very high, high energy is required to lift the follower.

Therefore, the pressure angle is usually kept as low as possible in the cam follower mechanism.

Cam follower design

Now, we discuss how to design a cam follower mechanism.

The design of cam profile is the primary step in manufacturing of the cam follower mechanism.

The cam profile depends on the size of the follower, type of follower, and the kind of motion required.

Constant velocity, constant acceleration and simple harmonic motion are some of the motions in cam and follower mechanism.

The cam profiles are different for getting the above motions.

Before discussing the cam profile, we should know about some terms.

Angle of ascend : The angular rotation of the cam during the ascend of follower is known as angle of ascend.

Angle of dwell: It is the angular rotation of the cam during the dwell period.

Angle of descend: It is the angular rotation of the cam during the return period.

Lift or stroke: The distance travelled by the follower during the rise or return period.

Now, let’s discuss designing a cam profile.

The critical step in designing the cam profile is drawing a displacement diagram.

The displacement diagram is the graph plotted between the angular distance of the cam and the lift of the follower.

The displacement diagram varies for different motions.

After getting the displacement diagram, we have to transfer the distance to the base circle to get the cam profile.

Displacement diagram

The displacement diagram for different motions is explained in this section.

The angle of ascend, dwell, descend, and lift of stroke are predefined variables.

Now let’s assume that the angle of ascend, dwell, and descend, and lift of stroke are 90o, 90o, 90o, and 10cm, respectively.

Drawing different displacement diagrams are explained below;

Constant velocity

  • Draw x axis and y axis, mark the angles in x axis and lift in y axis.
  • Mark the ascend, descent, and dwell in x axis.
  • Join the left bottom corner and right top corner in ascend to get the displacement of follower during the rice period.
  • During the dwell period, the displacement curve will be parallel to the x-axis.
  • Join the left top corner and bottom right corner for drawing the displacement curve during the descend.
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Constant acceleration

The figure shows drawing the displacement diagram for ascend.

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  • Divide the angle of ascend to even number of parts (n parts). And draw vertical lines.
  • Mark the center line and divide it into n parts.
  • Draw a line from the bottom left corner to each point in the centerline till n/2 parts, do the same for the remaining point from the top right corner.
  • Mark point of contact between 1st vertical line and 1st inclined line and 2nd vertical and 2nd inclined line and so on.
  • Join the points.

Simple harmonic motion

The figure shows drawing the displacement diagram for ascend.

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  • Divide the angle of ascend to n number of parts. And draw vertical lines.
  • Draw a semi-circle in the y axis with diameter equals to lift, divide it into n parts.
  • Now, draw a horizontal line from each point on the semi-circle to the corresponding vertical lines.
  • Joint the point of contact between the horizontal line and vertical line.

Drawing cam profile

The figure shows the cam profile for the constant velocity profile mentioned above.

The steps involved in drawing cam profile from displacement diagram are,

  • Draw the base circle.
  • Mark ascend, descend and dwell period in the base circle.
  • Divide ascend, and descend to equal parts similar to displacement diagram.
  • Measure the distance from the x-axis to the curve in displacement diagram for each vertical level.
  • Mark the measured distance from the base circle for each vertical level, respectively.
  • Join the pints
Cam profile Low 2

Cam and follower material selection

For most applications, the cam is manufactured using metals. Steel alloys and cast irons are most commonly used material.

The thermoplastic like nylon and polypropylene are used in some cases.

How to build a cam and follower?

Here we discuss the manufacturing technique used for producing cam and follower.

Initially, we have to design the cam and follower and study the forces acting, stress-induced, the maximum load the cam follower pair can handle, etc. Generally, SolidWorks software is used to design the cam and follower mechanism.

For thermoplastic materials, impact molding is used for manufacturing.

For metal cams variety of manufacturing techniques is used. Conventional manufacturing techniques like grinding, milling, cold forging, etc., are used to produce cam. For high accuracy, CNC machining is used. Powder metallurgical techniques are also used in many situations.

Degree of freedom of cam and follower

The degree of freedom of cam and follower should always be one.

The degree of freedom indicates the number of independent variables to define the motion of the system. Degree of freedom 1 means we need one independent variable to describe the motion. That means the movement between the links is only possible in one way. If we rotate the cam, the follower will only reciprocate; it will not reciprocate and oscillate together.

The constraints are provided to make sure that the degree of freedom of the system is one.

Applications of Cam and Follower

  • IC engines
    • Opening and closing of inlet and exhaust valve.
    • Operating fuel pump
  • Automatic lathe
    • feed mechanism
  • Toys
  • Wall clocks

Cam and follower advantages and disadvantages

Advantages of cam follower mechanism

  • By proper designing of cam profile, a variety of follower motions can be obtained.
  • Able to operate accurately.
  • Easy mechanism to convert the rotational motion to reciprocating or oscillating motion.
  • The number of components reduces with the use of a cam and follower mechanism.
  • Compact

Disadvantages of cam follower mechanism

  • Subjected to wear, hence, can be used only when the transmission force is less.
  • Accurate manufacturing is required.
  • High manufacturing cost.
  • There is a limitation to the size of the mechanism. Large size is challenging to operate.

Cam and follower objective questions

  1. During the rise or ascend period, the follower is;
    1. Moving up
    2. Moving down
    3. Stationary
    4. None of the above

Ans: 1

  1. In cam and follower, friction should be
    1. High
    2. Low
    3. Medium

Ans: 2

  1. The side thrust can be reduced if we use;
    1. Roller follower
    2. Knife edge follower
    3. Flat plate follower

Ans: 3

Cam and follower problem

Try to answer the given problem yourself,

  • Draw displacement diagram and cam profile for following conditions,

Follower Type: Knife-edge follower

Lift : 6 cm

Base circle radius: 6 cm

Angle of ascend: 60

Angle of dwell: 120

Angle of descend: 60

Motion type during ascend: Simple harmonic motion.

Motion type during descend: Simple harmonic motion.

Important Questions and Answer 

What is the difference between cam and follower?

Cam is the driver in the cam and follower mechanism, which reciprocates or rotates. The follower is the driven component, which oscillates or reciprocates. The ultimate aim of the cam and follower mechanism is to get the desired motion for the follower.

Cam and follower motion?

The cam and follower can have a different combination of motions.

The cam usually rotates(cylindrical, plate cams) or reciprocate (wedge cam)

The follower oscillates or reciprocate.

Is a cam follower a lifter?

Yes

Cam and follower types

A detailed description is given in the above content.

Why are ‘offsets’ required in cam and followers?

The offset is used to reduce the wear and side thrust.

In physics mechanics, how come a cam follower is a higher pair?

The classification of higher pair and lower pair is based on the contact between the links. The nature of contact is point (knife-edge follower) or line (roller follower) in the cam follower mechanism. Hence it is higher pair.

What is the significance of pressure angle in Cam followers?

The pressure angle indicates the steepness of the cam profile.

An increase in pressure angle leads to a decrease in the lift force and an increase in the thrust force. The lift force must be sufficient to overcome the spring force or gravitational force in the cam follower mechanism. Hence, if the pressure angle is very high, high energy is required to lift the follower.

Therefore, the pressure angle is usually kept as low as possible in the cam follower mechanism.

Why is the roller follower preferred over the knife-edge follower?

The roller follower is preferred over the knife-edge follower to reduce the friction, hence the wear of the follower.

What is the pressure angle and methods to control the pressure angle of a cam?

Pressure angle is defined at every point in the pitch curve.

It is the angle between the direction of the follower movement and the normal pitch curve.

Methods to reduce pressure angle;

  • Use offset follower
  • Increase the size of cam

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Schematic diagram of FBC boiler credit Wikipedia

advantages of cfbc boiler over afbc boiler | difference between afbc and cfbc boiler

AFBC means atmospheric – fluidized – bed – combustion. The speciality in this boiler is to keep furnace pressure at atmospheric conditions. The burnt gases developed in the combustion chamber are passes through the cyclone and are discharged into the atmosphere.

CFBC means circulating – fluidized – bed – combustion. In this kind of boiler, the furnace gas is pressurized to recirculate in the chamber. This recirculation of gases captures the unburnt carbon. Thus, the thermal efficiency of a boiler is increasing because of gas recirculation.

The comparison of the AFBC and CFBC boiler can be made based on the following parameters and criteria.

The velocity of the gases

In AFBC, It is around the 1.2 – 3.7 m/s

In CFBC, It is around 3.7 – 9 m/s

Heat Transfer Surface

In AFBC, The heat extraction can be done from bed only

In CFBC, The heat transfer was carried out bed and other surfaces of combustion chamber. It is known as the convective zone. The heat transfer from water walls is possible.

Fuel size

Coal is a widely used fuel in both boilers, but the size of coal particles in CFBC is 2-3 mm more.

Supply of air in combustion chamber

In AFBC boiler , The range  is  3 to 5 PSI gauge

In CFBC boiler, The range  1.5 to 2 PSI gauge

From above comparison we can say that the Performance characteristics of the CFBC boiler are better than the AFBC. It is an advanced technology of circulating gases. It is developed to solve some difficulties that arise in the AFBC. Some of them are discussed as below,

  • 1. The utilization space in the CFBC boiler is adequate than AFBC.
  • 2. The combustion of fuel is efficient more in the CFBC boiler.
  • 3. SO2 and NOx can be controlled more in the CFBC boiler.
  • 4. The control of temperature is more in the CFBC boiler.
  • 5. It can work effectively even with the low calorific value of the fuel.
  • 6. the turndown ratio is higher
  • 7. Both over & under feed systems can be used

afbc boiler working principle | afbc boiler start-up procedure

  • Following are the steps to be followed to start the afbc boiler
  • The air nozzles are cleaned by entering the full Fd air into the combustion furnace. Open the air compartment door for 10 to 15 minutes to complete this task
  • Enter the bed material into the combustion furnace. The bed height is to be around 250 to 300 mm above the nozzles.
  • The material below the nozzle is to be a static fix. It is also considered in the bed height
  • Enter the fluidizing air through the complete bed to uniformly distribute the bed materials over the bed. The PA damper is kept close during this operation
  • Open the startup compartment when you feel the uniformity in bed material and bed height.
  • Now increase the flow of air to develop tiny bubbles all over the bed material. This stage is called the bubbling stage. Read the airflow rate and note it down at this stage.
  • In the next step, Increase the furthermore the flow of air to make the bed turbulent. It is helpful for proper mixing of the upper and lower layer of the bed material. This is called the mixing stage. Read the airflow reading at this stage.
  • Switch off the fan and airflow rate. Now boiler is ready to start
  • The drum is level is to be maintained at around 40 %
  • Initiate firing
  • Keep initializing for few minutes, start All three fans as per sequence (ID, FD and PA)

afbc boiler design | accepted range of afbc boilers

The construction and working of AFBC with an explanation of various parts involved,

Main systems in the AFBC

  • Fuel supply system
  • Air Distribution
  • Heat transfer in Bed and surface
  • Ash Control system

Generally, these four main systems are included in every FBC boiler.

1. Fuel Supply System

There are two types of fuel supply systems in FBC boilers. Under-bed pneumatic supply and over bed supply.

The absorbent is used for fuel supply—examples: dolomite, limestone etc.

In under bed pneumatic supply, the coal is crushed and pulverized in 1 to 6 mm in size. This coal is supplied from the inlet hopper to the combustion chamber with the pneumatic arrangement. This system is developed according to capacity.

2. Air distribution system

The air distributor is the main component of any FBC boiler. It is utilized to pass or distribute the fluidized air from the furnace bed. The air distributor is keeping the solid particle motion at a constant rate. The air distributor is made from a metallic plate. The pattern geometry is made with the perforation in it. The nozzles are installed with perforation in it. This perforation is not allowing the solid particles to go back into space.

There are some arrangements made to protect the distributor from the temperature of the bed.

i) Refractory material Lining brick

ii) Fix layer of the materials in bed

iii Cooling tubes

3. heat transfer in bed and other surfaces

a)  heat transfer in Bed

The bed is made with particular kinds of materials like crushed limestone, refractory, ash and sand. The size of material particles is around 1 mm. There are two types of bed widely used beds in the FBC boilers.

(1) Shallow bed

(2) Deep bed

(1) Shallow bed

The power consumption of the fan is low in the shallow bed. In addition, the resistance of the bed is less in shallow beds, so the pressure drop is also lower.

(2) Deep bed

The power consumption of the fan is high in the deep bed. The resistance of the bed is more in a deep bed. The gas velocity is raising because of  pressure drop.

b)  Heat Transfer on surface

In the FBC boiler, the heat transfer should be sufficient within the bed material and the bundle of the tube or coils. The heat transfer is more superior in the horizontal orientation of the heat exchanger in shallow bed air distribution. There are few  parameters on which the heat transfer is depending,

Temperature of bed

Solid fuel particle size

Design and the layout of heat exchanger

Structure of the air distributor

Velocity of gas

4. Ash Handling System

a) Bottom Ash drain

There are two types of ash present in the FBC boiler. One is the fly ash, and the other is the bottom ash. Generally, the sediment ash is nearby 30 to 40 %. This ash is taken out when exceed limit to control bed height.

b) Removal of fly ash

The fly ash of the FBC boiler is more than other boilers. The combustion efficiency can be increased by utilizing the fly ash in some units. It is happening because the speed of the particle is very high. The fly ash travels with the flue gases, which is taken out at various stages from the FBC unit. There are three stages for the removal of the fly ash. (1) Convection part of FBC (2) Before air preheater or economizer (3) dust collector

There are many types of dust collectors available in the FBC boilers. (1) Cyclone (2) electrostatic precipitator (3) bagfiler (4) Combination of dust collectors

afbc boiler bed height calculation | afbc boiler bed height

The height of bed is calculated with the following equation in boiler,

level  of bed = Pressure in wind box – Differential pressure in the bed nozzles

DP test in afbc boiler | dp test procedure for afbc boiler

  • The first step is to precheck the bed with the following steps:
  • Make bed properly clean
  • Complete the maintenance of air nozzle and bed
  • The FD fan should work with higher efficiency
  • Steps of Procedure for DP test:
  • Initially start the ID fan, Start FD fan with minimum speed
  • Keep Air preheater inline
  • Raise the speed of airflow (Increase from 25% – 100%)
  • Read and note the pressure in the wind box at every stage
  • For all other compartments, repeat the same procedure
  • The value of pressure in the wind box needs to be nearby with designed values
  • Interpretation of DP test
  • The nozzle, bed plates are in good condition if the value of wind box pressure is nearby the designed value
  • The nozzles may be blocked if the value of wind box pressure is exceeded the design value
  • The nozzles may be damaged or defected hole if the value of wind box pressure is less than the design value

bed material size for afbc boiler |  afbc boiler bed coil

In the AFBC boiler, there are many grades of solid fuel (coal) available. The size of the coal particle is varied from 1 -10 mm. The size of coal particle is chosen based on the type of coal, quality of coal etc. The atmospheric air is used for two purposes, fluidizing air and air for combustion. First, this air is provided with sufficient pressure over the bed. Second, this is preheated by an air preheater in the boiler.

The velocity of this fluidizing air can be in the range of 1.2 – 3.7 m/s in the AFBC boiler. The flow rate of air passes through the bed can be utilized to determine fuel reaction. The bed temperature can be maintained by installing the bed evaporator tube to construct a limestone or sand bed. The bed evaporator tube helps reject the heat from the bed to maintain the temperature of the bed.

The bed is made up of depth  0.9 m to 1.5 m. the pressure drop across the bed is expected around 1 Inch per inch of depth of the bed.

The generated flue gases from the FBC combustion chamber is passed through the superheater section, economizer and air preheater. After air preheaters, the flue gases are exhausted from the atmosphere.

The AFBC boiler is famous for its temperature range. The temperature range of the AFBC boiler is 800 °C to 950 ° C. If the temperature exceeds this range, the boiler’s performance is decreased.

afbc boiler air nozzle

Two types of nozzles are widely used in the AFBC boiler.

Fluidizing nozzle:

This type of nozzle is made up of the S S or alloy steel. It is fitted on the bedplate. The hole size is about 2 – 5 mm. The air of the FD fan is entering from the wind box to the combustion furnace.

Coal feed Nozzle:

This nozzle is used to enter coal with air into the combustion furnace. The total number of nozzle is taken according to the size and capacity of the boiler. It may be 4 -6 nozzles. It is also fitted on the bedplate.

afbc boiler bed material density

The material density of the bed is around 1100 kg/m3

afbc boiler efficiency | afbc boiler efficiency increase

The combustion efficiency is depending on the following parameters :

(1) Reaction properties of fuel

(2) Volatility of fuel

(3) Size of the fuel particle

Coals like sub-bituminous or lignite are highly efficient in burning. There is no fly ash recycling or under a bed; feeding requires if the coal quality is good. The combustion efficiency of the AFBC boiler is in order of 70 to 99 %. The combustion efficiency is decreased. The efficiency of the AFBC boiler can be achieved by system improvement. The coal-like anthracite burns with low efficiency in the AFBC boiler. It can burn with higher efficiency in the CFBC boiler with the applications of fly ash recycling and the under bed feeding.

afbc standard boiler parameters

The following are the standard parameters which the of the AFBC

  • Size of the coal particles
  • Specification and size of the bed material
  • Air pressure from the FD fan
  • Height of the bed
  • Temperature of furnace
  • The temperature of the bed

afbc boiler velocity of flue gas | flue gas velocity in afbc boiler

The velocity of this fluidizing air can be in the range of 1.2 – 3.7 m/s in AFBC boiler.

afbc boiler interview questions and answers

What steps will you follow if the temperature of the bed increases?

The following are the points to be considered if the temperature of the bed is raising,

  • Load reduction
  • Maintain the density of the coal
  • Increase the material of the bed

What are the probable facts for the decrement in bed temperature?

  • The following are the probable facts for the decrement in the bed temperature,
  • The quality of material used in bed is poor
  • Suddenly action of the boiler load reduction
  • Excessive air entered the furnace
  • Fuel contains moisture

What is the reason behind the use of lime in the AFBC?

The coal contains some moisture, which has to be removed before combustion for better combustion efficiency. The purpose using lime is to absorb and remove the moisture from the fuel.

Which one is superior CFBC or AFBC ? Explain why?

We can conclude that the Performance of the CFBC is more superior to the AFBC. It is an advanced technology of circulating gases. It is developed to solve some difficulties that arise in the AFBC. Some of them are discussed as below,

1. The utilization space in the CFBC boiler is adequate than AFBC.

2. The combustion of fuel is efficient more in the CFBC boiler.

3. SO2 and NOx can be controlled more in the CFBC boiler.

4. The control of temperature is more in the CFBC boiler.

5. It can work effectively even with the low calorific value of the fuel.

6. the turndown ratio is higher

7. Both over & under feed systems can be used

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Analog Instruments: 23 Important Facts You Should Know

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Content: Analog Instruments

What is Analog Instruments ?

Analog Electronic Instruments

An analog instrument is one whose output or display is a continuous-time function. This instrument converts the input quantity into an analog O/Ps; having an infinite number of value. An analog instrument typically contains a pointer and a scaled calibrated dialler to show the output.

analog instrument
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Selecting factor of Analog Instrument:

Types of Analog Instruments

The analog instrument can also be of two types:

The direct measuring instrument is the instrument that converts the energy of the measuring quantity directly into energy that trigger the instrument, and the magnitude of quantity to be measured instantly.

A comparison instrument that compares the unknown quantity with a standard, when high accuracy is needed, is used.

One more classification of the analog instrument is

Analog Indicating Instruments

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Image Credit: “Scale Face” by ‘Playingwithbrushes’ is licensed under CC BY 2.0

It is indicating instrument that show the instantaneous value of the magnitude of the quantity to be calculated. The indicating instrument typically includes all null types of instrument and most passive ones. The most used is a dial and a pointer indication by the pointer moving over a calibrated dial.

The analog indicating instrument can be divided into two groups electromechanical instrument and electronic instrument.

Examples are ammeter and voltmeter.

Recording Instruments

The recording instrument gives a continuous record of the variation of the quantity being measured over a specific period. Although it is used to provide the overall performance of any instrument, it can provide data to evaluate the calibre and efficiency of the operating crews.

Types of Recording Instruments

 Analog Recording Instruments can be of three types:

What is Graphic recording instruments ?

Graphic recording instruments display and store records of the history of some physical event with pen and ink. They even may be varying voltage, current, pressure, etc. It mainly consists of a chart for storing and displaying recorded data. This stylus moves on paper with proper relationship and an internal connection which connects the stylus to the information source.

Integrating Instruments

An integrating instrument is an instrument to find the sum of measurements over a specific period the summation in which this provide as product of time and the measured quantity.

Principle of Operation of Analog Instruments

Operating Torques in Analogue Instruments are

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Operating force or torque:

Deflecting Force or torque: It is a force or torque which reflects the pointer from its 0th position of calibrated scale according to the magnitude of the quantity passing thru the device.

Controlling Force or torque:  which control the movement of the pointer on a required scale. It is needed to bring the pointer to the 0th point at if no deflecting force. To produce an equal and opposite force to the deflecting Force to make the pointer steady in the absence of controlling Force pointer may swing away from the final study position for any magnitude. Controlling torque can be produced by Spring control gravity control.

Damping force or Torque: This used to prevent from the vibration for oscillation of the pointer on a particular range of scale; It is required to bring back the pointer at rest. Damping force can be established by air friction fluid friction Eddy current damping.

Magnetic Effect

In a uniform magnetic field, a current-carrying conductor is situated, which result in a disturbance in the magnetic field, impacts force (F). The direction of Force will be the opposite direction of the current and coil conductor generate magnetic field act as magnetic material.

Force of attraction or repulsion 

When a piece of soft iron that is not magnetized previously, kept near the end of the coil. When current flow through the coil, the soft iron becomes magnetised and gets pulled inside the coil. The Force of attraction is proportional to the field strength inside the coil and proportional to the current strength; utilized in attractive moving iron (M.I) instrument.

If two soft iron pieces are situated near the coil, become magnetized, and then there will be repulsion force; utilized in repulsive moving iron (M.I) instrument.

The Force between a current-carrying coil and a permanent magnet is used in a permanent magnet moving coil instrument, and Force among 2 current-carrying coil is utilized as the key principle in dynamo meter type of instrument.

Thermal Effect

The current to be measured is passed through a heating element whose temperature increases with the increase in current and temp change is converted into an EMF by a Thermo-couple. The thermocouple is designed with two dissimilar electric conductors joined together at the end of each other to form a close loop, the point the dissimilar metal meets is the junction. If both the junction is maintained at a different temperature, a current will flow through the loop.

Electrostatic Effect

The electrostatic effect is the attractive force among 2 or many electrically charged elements between which a potential diff is preserved. That force results in to increase in deflecting torque. The electrostatic effect is the basic principle of an electrostatic instrument known as an electrometer voltmeter, an example of an electrostatic instrument.

Advantages of electrostatic instrument:

Disadvantages of electrostatic instruments:

Induction Effect

Induction effect when a non-magnetic conducting disc or drum is placed in the magnetic field which is excited by alternating currents, EMF will be induced in the drum or disc. If the closed path is provided, then EMF will cause a current flow to the drum or disc. the produced force in the interaction of the induced current and the magnetic field will cause the disc or drum to move this effect is used in energy meter.

Advantages of induction instruments:

Disadvantages of induction instrument:

Errors in the induction instrument are due to frequency variation or temperature variation.

Hall Effect

This is the formation of potential difference across a conducting material having electrical current exist in a cross magnetic field.

The magnitude of the potential drop depends on the current flux density, and the internal property of the conductor is called the hall effect coefficient. The emf produced in this phenomenon is so small for measurement, which may require amplification. Hall effect instruments are used for sensing current or in magnetic measurement. Examples are flux meter ammeter Poynting vector watt-meter. Hall effect instruments convert the magnetic field into electric quantity, which can be easily be measured.

Advantages of hall effects:

Disadvantages of hall effects:

What are the advantages of digital instruments over analog instruments?

Advantages and Disadvantages of Analog and Digital Instruments.

Advantages of Digital Instruments over Analog :

Disadvantages of Digital Instrumentation:

Advantages of Analog Instrumentation:

Disadvantages of Analog Instrumentation:

Analog Devices Instrumentation Amplifier

Analog devices instrumentation amplifier when the output of any instrument is low or needed any amplification for further processing the input to the instrument amplifier is the output from the centre of the transducer used to amplify, reject noise and signal interference. An instrumentation amplifier is a differential amplifier, and an analog device instrumentation amplifier is a precision block with a differential input and output. This device amplifies the differences between the two input signal voltages while rejecting signals common to both inputs.

Analog Instrument Cluster |Instrument Cluster Analog

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Image Credit:“Hawker Hunter Cockpit” by G. Weir is licensed under CC BY 2.0

An analog instrument cluster is a group of different analog instruments, and it can include different analog metres and gauges to provide the required measurement. These clusters are used for safety order requirement mainly used in automobiles, aircraft etc. this cluster use different m for measuring required information, for example, in automobile, speed, fuel level, charge level, etc.

What is the difference between Digital and Analog Measuring Instruments ?

Comparison between Analog and Digital instruments

Analog InstrumentDigital Instrument
Low PrecisionHigh Precision
High power RequirementLow Power Requirement
Highly SensitiveLess Sensitive
CheapExpensive
Less ResolutionHigh Resolution
Not compatible directly with a computer, microprocessor or microcontrollercompatible directly with a computer, microprocessor or microcontroller
More FlexibleLimited flexibility
Parallax error during reading result is possibleNo reading error due to digital display
Can get easily affected by noiseHigh noise immune
Easily portableNot easily portable
Continuous convenient for readoutConvenience in readout

Electronic Test Instruments Analog and Digital Measurements

Electronic test instrument testing instruments are used to detect a fault in operation, such as voltmeter, ammeter, ohmmeter, multimeter, frequency counter, oscilloscope or LCR meter, etc.

The testing instrument is the key to any electronic design production and maintenance. It can be an analog or digital instrument used to generate a signal and capture the response from the device Under test.

Analog Aircraft Instruments

Following are the analog instruments which are used in aircraft:

The altimeter is a device used to measure an object’s altitude relative to a fixed level. It has two types of pressure altimeter and radio altimeter and study of altitude is known as altimetry. 

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Image Credit:“Aircraft altimeter” by cambridgebayweather is licensed under CC BY-SA 2.0

A pressure altimeter calculate altitude as per atmospheric pressure. With the increase in altitude, the pressure reduces. Radio altimeter determines the height of any subject by sending a signal to the ground and measure the attitude based on the time required for the radio wave signal to travel. Altimeter having mechanical internal aneroid capsule have an analog display.

Air speed indicator is used to measure the aircraft’s speed; It uses a pitot tube which is U shaped with two openings .airspeed indicator traditionally is a mechanical analog instrument.

Magnetic compass and instrument for determining direction by using a magnetic element which shows the direction of the horizontal component of the magnetic field of the earth

The tachometer is a device that indicates the rate of rotating an object or engine shaft; it includes the instantaneous value of speed in RPM. It is composed of a tile and little to indicate the immediate reading.

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Analog Polygraph Instrument

An analog polygraph instrument is commonly known as the Lie Detector instrument, measuring at least three physiological responses like blood pressure, pulse respiration, and skin connectivity.

It can consist of pneumographs to record respiratory activity, blood pressure cliff to record cardiovascular activity,  and galvanometer activity sensor, plethysmograph, etc. The analog polygraph needles draw the line on a paper to record and show the output. These lines represent the level of stress which can affect if the person is telling a lie.

Analog Weather Station Instruments

Analog weather instruments:

The thermometer is used to measure the temperature of the environment. There are many types of thermometers. One of the most used thermometers is a thermistor designed with metal oxide and has a high-temperature Coefficient, so with the temperature change, the resistance shift occurs.

Thermistor mainly has negative temperature Coefficient. Although the increase in temperature resistance decreases, it is very sensitive to temperature change, making thermistors useful for Precision temperature measurement.

A barometer is an instrument uses to measure the pressure of the atmosphere because atmospheric pressure varies with altitude. A simple barometer is a mercury-in-glass barometer unit of measurement. The atmosphere or bar Mercury glass parameter is closed at the top and open at the bottom. Thus, there is a pool of Mercury. 

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Image Credit :“Barometer” by electricinca is licensed under CC BY-SA 2.0

The aneroid barometer is a non-liquid barometer that is widely in use. It is small and uses an evacuated capsule as a sensing element, the flexible walled evacuated capsule. The flex with the change in atmospheric pressure the deflection is coupled mechanically to an indicating needle.

A hygrometer is a device that indirectly measures humidity by sensing a change in physical or electrical property in materials, which causes due to moisture content. There are different types of hygrometers for humidity measurement. In mechanical hygrometer measures humidity with the change in length of the hair element by the contraction and expansion of the hair element. 

A rain gauge is a device that is used to measure rain in a certain period. It usually measured rainfall in millimetres. There are different types of rain gauges. The most precise one is the ground level gauge, where the orifice of the gauge is placed with the ground level surface and surrounded by an anti-splash grid.

Anemometer is a device that measures the rate of flow, which can be used for measuring airflow. A hot wire anemometer is widely used for measuring the mean and fluctuating velocity of fluid flows. Steam of air will cool down a heated object is the principle of hot wire anemometer a heated wire is placed in the airflow.

Pyranometer is an instrument that is used to measure solar radiation. It is operated on the measurement of the temperature difference between a bright surface and a dark surface. There are different types of pyranometers, such as thermopile pyranometers, photovoltaic pyranometers, etc.

Examples of Analog Instruments

Uncertainty for Analog Instruments

Uncertainty of analogue resolution uncertainty is one of the problems in analogue instruments. It considers the limitation of measurement. The Precision accuracy of a measurement is limited by the resolution of the instrument for an analog instrument with gradual scaling sometimes causes parallax error when taking a reading from different view position will give different reading leads to an error which creates uncertainty in measurement.

Frequently Asked Questions.

What are absolute and secondary instruments?

Absolute Instrument:

These instrument provides the magnitude of the measuring quantity in terms of physical instrumental constant. 

Secondary instrument:

These instrument convert the analog o/ps  of the primary/absolute instrument into an electrical signal. These instruments are required to be calibrated by comparison with an absolute instrument that has already been calibrated.

Analog Instruments are preferred for ?

Error in Analog Instruments ?

three different types of error that happen in any instrument:

  •  Instrumental Errors: These errors are caused by miss-use of the instrument, loading effect, ageing or inherent shortcomings.
  •  Environmental Errors: These errors are caused by external condition of the instrument, hence errors are may affect by surroundings temp, pressure, humidity, dust, etc.
  •  Observational Errors: these errors occur due to human observational factors. There can be reading parallax error in analog instruments, which is an observational error. Different moving parts in an analog instrument can produce an error when friction between two components is created, an instrumental error. Ageing of the instrument can produce an error is also an instrumental error. 

What are some examples of common Analog Devices ?

What are the Comparative Advantages and Disadvantages of Digital and Analogue Multimeters ?

What is a Micrometer ?

Micrometer is also known as micrometer caliper or micrometer screw gauge. It is an instrument for measuring linear(small) distance precisely, such as diameter, length, thickness, etc. 

How does an Ohm Meter Measure Resistance ?

Ohm meter can not measure resistance directly but can measure the power through a circuit. Any known voltage is connected to a component whose resistance is measured, where resistance is unknown by measuring the current through the measuring component. Through Ohm’s Law relationship between voltage current and resistance is known. Therefore, we can calculate the value of the unknown resistance by finding current through the circuit as the voltage is known.

Is Wifi a Digital Signal or an Analog?

The wifi signal is both analog and digital and for that ,  ADC  and DAC and modulation of the signal takes place as requirements.

What is Wattmeter and its construction?

A wattmeter is an instrument that measures the electrical energy of a circuit. The unit of measurement is in watts. It can be an electro-dynamometer or induction watt meter. It can be constructed with a current coil and voltage coil, the current coil is adjoining in series connection, and the voltage coil is connected by parallel connection. The needle which moves on the calibrated scale is connected to the voltage coil. The voltage coil is a moving coil, whereas the current coil is immobile.

How to find Multiplication factor for Wattmeter ?

Multiplication factor = (voltage range X current range X power factor)/(range of wattmeter)

Is there anything that an Analog Multimeter does better than Digital one If so Why ?

Analog multimeters are suitable for measuring fluctuating values better than that of digital multimeters, because sudden fluctuation can not be precisely represented by digital multimeters. While analog multimeter has changing display which can accurately show the sudden fluctuations, it may not provide exact reading but it will provide instantaneous and rough measurement.

D Type Flip Flop : Circuit Diagram, Conversion, Truth Table, Applications

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What are the different types of a flip flop?

D flip flop Types

Level triggered D flip flop

D flip-flop whose output changes according to the input with a high level of the clock pulse is a level triggered D flip-flop, and then the clock level is low, the D flip-flop stays in a hold state.

What is Edge Triggered D type flip flop ?

D type Edge Triggered flip flop

D edge triggered flip-flop is the flip-flop in which the output can change only with the edge of the clock pulse, regardless of the change in the input. That means the output of the flip-flop changes with the transition of the clock pulse, either from high to low to high. 

D type Edge Triggered flip flop type

Edge triggered D type flip flop can be of 2- types:

The edge triggered flip Flop is also called dynamic triggering flip flop.

Edge Triggered D flip flop with Preset and Clear

Edge Triggered D type flip flop can come with Preset and Clear; preset and Clear both are different inputs to the Flip Flop; both can be synchronous or asynchronous. Synchronous Preset or Clear means that the change caused by this single to the output can affect the clock pulse; here, it is edge triggered to change with the edge of the clock pulse. Whereas Asynchronous Preset can Clear can change the output at any instant of time.

Edge Triggered D flip flop Timing Diagram

The given timing diagram shows one positive type of edge triggered d flip flop; there is clock pulse CLK, D the input to the D flip flop, Q the output of the D flip flop; as you can see, the changes in output are happening during the transition of the clock pulse from low to high, because it is a timing diagram of a positive edged D type flip flop.

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Fig. Time diagram of a positive edge triggered type d flip flop

Edge Triggered D flip flop Circuit Diagram

The circuit diagram of the edge triggered D type flip flop explained here. First, the D flip-flop is connected to an edge detector circuit, which will detect the negative edge or positive edge of the clock pulse. Then, according to the output of the edge detector circuit, the D flip flop will operate accordingly.

d flip flop types
Fig. Circuit diagram of edge triggered d type flip flop

Edge Triggered D flip flop Truth Table

table 1
Table: Truth table of edge triggered D type flip flop with input and output values.

Rising Edge Triggered D flip flop | Positive Edge D flip flop

The positive edge D type flip flop, which changes its O/P according to the I/P with the +ve transition of the clock pulse of the flip flop, is a positive edge triggered flip-flop. It has high-speed performance with low power consumption, that is because it is widely in use. The positive edge D type flip flop can be represented with a triangle at the D flip-flop block diagram at the clock end. 

Positive Edge Triggered D flip flop Circuit Diagram

The Positive edge triggered D type flip flop circuit can be designed with three latches, where two input latches are adjoining with the clock pulse, one latch is attached with the input data, the circuit is designed in such a way that the output response happens only at positive transition of the clock pulse.

d type flip flop
Fig. Positive edge triggered D type flip flop.

Positive Edge Triggered D flip flop Timing Diagram

Clock pulse CLK, D the input to the D flip flop, Q the output of the D flip-flop, the changes in output is happening during the transition of the clock pulse from low to high.

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Fig. Timing Diagram of +ve edge triggered D flip flop.

Positive Edge Triggered D flip flop Truth Table

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Table: Positive Edge Triggered D flip flop Truth Table with input and output value.

Falling edge Triggered D flip flop | Negative Edge Triggered D flip flop

The D flip-flop, which changes its output according to the input with the -ve. transition of the clock pulse of the flip-flop, is a -ve. edge triggered flip-flop. The negative edge D flip-flop can be represented with a triangle and a bubble at the clock end of the D flip-flop block diagram.

Negative Edge Triggered D flip flop Circuit Diagram

The -ve edge D flip flop can be designed by adding a -ve edge detector circuit with the clock pulse. The -ve edge detector detects the -ve edge of the clock pulse. According to the O/P of the detector circuit, the rest of the circuit will operate. When there is a negative transition in the clock pulse, the circuit produces output according to the input. Otherwise, the circuit stays in a hold state.

Picture9
Fig. Circuit diagram of negative edge triggered D flip-flop.

Negative Edge Triggered D flip flop Timing Diagram

Clock pulse CLK, D the input to the D flip flop, Q the output of the D flip flop, the changes in output is happening during the transition of the clock pulse from high to low; this is the characteristic of the negative edge flip flop.

Picture10
Fig. Timing diagram of negative edge triggered D flip-flop

Negative Edge Triggered D flip flop Truth Table

table 3 2
Table: Negative Edge Triggered D flip-flop Truth Table with input and output value.

Master Slave D flip flop | MS D flip flop

Master Slave flip-flop was designed to make synchronization more predictable. To avoid race around conditions, a master slave flip-flop is also known as the pulse-triggered flip Flop because the response time of the output is equal to the width of the one clock pulse.

  Master slave D flip flop can be configured from 2-D flip-flop; each flip-flop is connected to a CLK pulse complementary to each other. One flip-flop as Master and the other act as a slave; when the clock pulse is high, Master operates and slave stays in the hold state, whereas when the clock pulse is low, the slave operates and the Master stays in a hold state. The O/P of the Master is feed into the slave flip-flop as I/P.

How to design Master Slave D flip flop using NAND gates ?

Master Slave D flip flop Circuit Diagram

The master slave D flip flop is designed with NAND gates, configured with 2-D flip-flops, one a latch with the gated circuit, as a master flip-flop, and the other work as a slave flip-flop with a complemented CLK pulse to each other.

Picture11
Fig. Circuit diagram of Master Slave D flip-flop designed with NAND gate.

Master Slave D flip flop Truth Table

DQ(PREVIOUS)CLOCKQ
0010
0110
1011
1111
0000
0101
1000
1101
Table: Master salve D flip-flop Truth Table with input and output value.

Timing Diagram of Master Slave D flip flop

In the given diagram, a signal of the CLK pulse, D the I/P to the master flip-flop, Qm is the O/P of the master flip-flop, and Q is the O/P of the slave flip flop. Thus, the behavior of a master slave D flip-flop can be observed through its timing-diagram.

Picture12
Fig. Timing Diagram of the Master-Slave D flip-flop.

Master Slave Edge Triggered D flip flop

If the master slave circuit is designed with edge triggered D flip flop, or in addition to D flip-flop circuit, there is one edge detector circuit, which detects the edge of a clock pulse. According to the output of the detector, the Flip-flop works. Then the overall circuit is a master slave edge triggered flip flop circuit.

D flip flop Design

D flip flop can be configured in many ways, like it can be created with NAND gate, NOR gate, Multiplexer, etc. It can be derived from other flip flops like JK flip flop, SR flip flop, or T flip flop. It can be designed with the help of many different combinations of the circuit with the clock.

How to design D flip flop using NAND gate ?

D flip flop circuit diagram using NAND gates

The D flip flop can be designed with NAND gate only, here one SR latch is designed with NAND is gated with two more NAND gates, and the clock pulse is input to the gated NAND with Data input, where one NAND gate D as input and the other NAND gate gets D compliment as one input. And according to the gated output, the SR latch is processed. The resulting circuit is a D flip flop circuit.

Picture13
Fig. D flip flop circuit designed with NAND gates

How to design D flip flop using NOR gate ?

D flip flop using NOR gate

The D flip flop can also be designed with NOR gates; here, three SR latches with clock pulse are used to develop the D flip-flop. The two input SR latch create the D and D complement output separately, and that output is feed into the third latch, which produces Q and Q-compliment as output. 

Picture14
Fig . Circuit Diagram of D flip flop designed with NOR gates

When there is no clock pulse, the initial latches get locked with the current state because of the interconnections, which cause the whole flip Flop to put on a hold state; regardless of the change in input data, the output cannot change.

D flip flop using 2 D Latches

Picture5
Image Credit :jjbeard, Public domain, via Wikimedia Commons

Transparent latch D flip flop

Picture16
Image Creditr:Glpuga – Author’s own work., Public Domain,

What is D flip flop SR Latch circuit diagram ?

Picture17
Fig. D flip-flop designed with SR latch

How to design D flip flop Using CMOS ?

D flip flop using CMOS Transistors

 

Picture18
Fig. D flip flop CMOS circuit designed with PMOS and NMOS.

Design D flip flop using Transmission Gate

The D flip flop can be designed with a Transmission gate, which reduces the complexity of the circuit as it reduces the number of transistor counts. When LOAD =0, the Latch stores the data input; when LOAD = 1, the latch is transparent. The transmission gate also helps to reduce the overall circuit size.

CMOS D flip flop Schematic

Picture19
Fig. Schematic diagram of D flip flop designed with Transmission gates.

D flip flop using 2×1 MUX

Picture21
Fig. D flip flop designed with a multiplexer (MUX).

D flip flop using MUX Explanation

A D flip flop can be designed with a single multiplexer(MUX), data ‘D’ is an input to the MUX, and the other input of the MUX is the feedback of the multiplexer output Q to itself’s input, the clock signal is acting as select line, If the clock (CLK) = one then the output of the MUX is D, otherwise the output of the MUX remain the past output Q. 

How to Design D flip flop using JK flip flop ?

Conversion of JK flip flop to D flip flop

D will be the external input to the JK flip flop, and JK flip flop is the universal flip Flop; we can design D flip-flop from the JK flip flop if we connect the K input of the JK flip flop with an inverter to the J input. Then the resulting circuit will be D flip-flop with I/P as D and O/P as Q and Qbar.

Picture22
Fig. Block representation of D flip flop designed from JK flip flop.
Inputoutput
JK flip inputflop

DQnQn+1JK0000X010X11011X111X0

Table: Conversion table from Jk flip flop to D flip flop with input and output values.

Where Qn+1 means the next output state and Qn means the present output state in the conversion table.

How to design Frequency Divider Circuit using D flip flop ?

D type flip flop Frequency Divider | D flip flop Clock Divider

A frequency divider is a digital circuit that divides an input frequency by a required factor. One such frequency divider is designed with a D flip flop, which divides the input clock frequency by two. One inverted feedback is from output Q to the input D is forming this frequency divider circuit.

Picture4
Fig. Frequency divider circuit designed with D flip flop and NOR gate.

Divide by 3 Circuit using D flip flop

The given circuit divides the input frequency by three. In this circuit there is 2 D flip-flop is used, and one NOR gate, which forms the resulting circuit, divides the input frequency by three.

Picture3
Fig. Frequency divider circuit designed with D flip flop which divide the frequency by 3.

Phase Detector using D flip flop

A phase frequency detector is a circuit used to detect the difference of frequencies and phase of two given inputs. The UP signal is generated when the clock signal is slower than the reference clock signals. The down signal is generated when the clock signal is faster than the reference clock.

Picture2
Fig. Phase frequency detector using two D flip flops.

The phase frequency detector can be designed with two D flip-flop as shown in the above figure; both the flip flop has different clock frequencies as input, and the reset of the flip flops are connected with a NAND gate whose input is the Down and Up signal.

Frequency Multiplier using D flip flop

The frequency multiplier is a digital circuit that generated the multiple of the input clock frequency signal. 

Picture1 2
Fig. Frequency multiplier designed with D flip-flop and inverters.

The circuit can be designed with the D flip-flop and even the number of inverted in the feedback line. The feedback is started from the output Q and goes to the NOR gate, which is attached with the clock input of the Flip Flop. The multiplier circuit output depends on the delay produced by the inverters; with different delays, we can produce different frequencies as output.

D flip flop Oscillator

The oscillator is a circuit that generates repeated and alternating waveforms. The oscillator can be designed with D flip-flop, where D flip-flop must be in a toggle, so whenever it gets a high input, the output value should toggle; for creating toggle flip flop from d flip flop, the complementary output of the D flip-flop is feedback to the Data input of the D flip-flop.

D flip flop Register

A register is a group of flip flops that can store more than one bit at a time, depending on the number of flip flops in the register.

What are the Quad D flip flop IC ?

Quad D type flip flop 74175 | Quad D flip flop 7475

Quad d flip flop is available in Ingratiated circuitry, which has 16 pins. It has a 4 d flip flop with separate input(D) and output ( Q and Qbar ) pins. The remaining pins are one ground, one clear, one clock, and one voltage supply pin. Its function is equivalent to the TTL 74175. It contains edge triggered D flip flop.

Hex D type flip flop

It is a type of d flip flop available in IC, which contains 6 d flip flops each has different input and output pin in the integrated circuit. Thus, it has 16 pins with one clock pin, one ground pin, one voltage supply pin, and one clear pin.

8 bit Octal D flip flop

Octal d type flip flop is commercially available as an Ingratiated circuit. It contains 20 pins, which have three-state output. All the flip-flops are mainly controllable by the clock and enable pin. Each flip Flop has different input (D) and output (Q) pins. The remaining pins are one clock pin, one ground pin, one voltage supply pin, one clear pin. This Ic is used to design a storage register, pattern generator, etc.

16 bit D flip flop

 It is a type of D flip flop available in IC; mainly a 16-bit edge triggered d flip flop with three-state output, designed for driving highly capacitive or low impedance load. It can be used as a 16 bit flip Flop, also can be used as two 8 bit flip flops. It has 48 pins, whereas each flip Flop has separate pins for input and output; two clock pins and two enable pins. It is used in designing buffer registers, input or output ports, bidirectional buses, etc.

Exhaustive Vhdl Code & Verilog Code: 27 Important Facts

vhdl code verilog code 0

 Content :

Verilog was originally for stimulation and verification of digital circuits, it is a hardware description language (HDL). Here, all the code is designed with D flip flop whether VHDL or Verilog code.

Verilog Code for D flip flop using NAND gates

module nand_g(c, a, b); //*each module contains statements that defines the circuit, this module defies a NAND gate which is named as nand_g*//

input a, b; / a and b is the input variable to the NAND gate
output c; / output variable of NAND gate is defined
assign c = ~(a & b); / this assign is used to derive the value of c through a and b
endmodule /module end with endmodule statement

module not_g(e, f); / this block defines the NOT gate
input f; / f is the input variable to the NOT gate
output e; / e is the output variable of the NOT gate
assign e = ~f;
endmodule

module d_ff_st(q_out, qbar_out, d_in, clk_in );
 //* this module defines a d flip flop which will be design with NAND gate and NOT gate *//
input d_in, clk_in; / input variable of D flip flop d_in is the data input and clk_in is the clock input 
output q_out, qbar_out; / output of the D flip flop q_out and qbar_out where q_out and qbar_out is compliment to each other

not_g  not_1(dbar, d_in); /NOT gate module is called with dbar and d_in parameter

nand_g nand_1(x, clk_in, d_in); /NAND gate module is called with x, clk_in and d_in parameter
nand_g nand_2(y, clk_in, dbar); /NAND gate module is called with y, clk_in and dbar parameter
nand_g nand_3(q_out, qbar_out, y); / NAND gate module is called
nand_g nand_4(qbar_out, q_out, x); / NAND agte module is called
endmodule

Verilog Code for D flip flop with Asynchronous Reset

module dflip_flop_asy_rst (q, d_in, clk_in, reset_in);

input d_in, clk_in, reset_in; / input variables  of the d flip flop is defined
output reg q; / output variable of the d flip flop is defined
always@ (posedge clk_in or posedge reset_in) 

//* always block is the block who's statements are executed sequentially here the block will executed when clk_in is in positive edge or reset_in is in positive edge *//

if (reset_in) / if reset_in is high or true then q <= 1'b0 
q <= 1’b0; / here 1'b0 means one bit number value zero
else / if reset_in is low or false then q<= d_in
q<=d_in;
endmodule / end of the module
verilog
fig. Block diagram of D flip flop designed from the above Verilog code.

Verilog Code for D flip flop using Dataflow Modelling

//* 
Dataflow modeling provides the descriptions of combinational circuits by their function rather
than by their gate structure.*//

module dflipflo (q, d_in, clk_in); / module defines d flip flop in data flow modelling

input clk_in, d_in ; / input variable of the d flip flop

output q; / output variable of the d flip flop

assign q = clk_in ? d_in : q; / if clk_in is true the q = d_in and if clk_in is flase the q = q

endmodule
d ffff
Fig. Diagram of d flip flop designed with the above dataflow code.

D flip flop Behavioral Verilog Code

//* Behavional is used when cicruit is sequential circuit it contain procedural statements *//
module dflip_flop_bh (q, d_in, clk_in); 

input d_in, clk_in; / input variable of d flip flop is defined
output reg q; / output variable of the d flip flop is defined

always @ (posedge clk_in) / the block is takes place continuously when clk_in is in its positive edge of the pulse

if(clk_in) / if clk_in is high or true then q<=d_in
q<=d_in;
endmodule

Verilog Code for Shift Register using D flip flop

//* this code is used to designed 4 bit shift register using d flip flop, here left to right shifting is taking place through this code*//
module shift_reg_LtoR (out, clock, reset_in, in);/ this module define left to right shift register of 4 bit

input in, clock, reset_in; / input variable is defined
output out;
output reg [3:0] s; / output varible s is defined as a register that can have 4 bit value

always@ (posedge clock, negedge reset_in) 
//* the sensitivity of this block is negative edge of reset_in or positive edge of clock *//
\t
if(!reset_in) / if else statement
s<=4’d0;
else
s<={ s [ 2 :0], in}; //* as s can have 4 bit value the s[2 : 0] has 3 bit and in has 1 bit, together they produce the 4 bit of s *// 
assign out= s[3];
endmodule

4 bit Ripple Counter using D flip flop Verilog Code

//* following code is for 4 bit ripple counter designed with d flip flop*//
module dff_r (input d_in, clk_in, rst_in, output reg q, output q_n); 
//* module define a d flip flop with clock, reset, d, as input, and q and qbar as output *// 

always@(posedge clk_in or negedge rst_in) //* this block sensitivity is positive edge of clk_in pulse or negative edge of rst_in *// 

if (! rst_in) / if rst_in is low or false the q is implemented with zero
q<=0;
else
q<= d_in;
assign 
 q_n <= ~q;
endmodule

module ripple_c (input clk_in, rst_in, output [3:0] o); / this module define the ripple counter of 4 bit
wire q_0, qn_0, q_1, qn_1, q_2, qn_2, q_3, qn_3; / wire is used to define the output or input signal 

 //* implementing d flip flop module with different parameter 4 times *//
dff_r dff_0(.d_in(qn_0), .clik_in(clk_in), .rst_in(rst_in), .q(q_0), .q_n(qn_0));
dff_r dff_1(.d_in(qn_1), .clik_in(q_0), .rst_in(rst_in), .q(q_1), .q_n(qn_1));
dff_r dff_2(.d_in(qn_2), .clik_in(q_1), .rst_in(rst_in), .q(q_2), .q_n(qn_2));
dff_r dff_3(.d_in(qn_3), .clik_in(q_2), .rst_in(rst_in), .q(q_3), .q_n(qn_3));

assign o={qn_0, qn_1, qn_2, qn_3};

endmodule

Positive Edge Triggered D flip flop Verilog Code

module pos_edge_df (q, d_in, clk_in, rst_in);
 //* this module define d flip flop with q as output and data, clock and reset as input *//

input d_in, clk_in, rst_in; / input variable of the d flip flop is defined
output reg q; / output variable of the d flip flop is defined

always @ (posedge clk_in) / this block is implemented continuously with every positive edge of the clock pulse

if ( !rst_in) / if else statement
q<= 1’b0;
else
q<=d_in;

endmodule
0000 1 edited 1
fig. Block diagram of D flip flop designed from the above code.

Negative Edge Triggered D flip flop Verilog Code

module pos_edge_df (q, d_in, clk_in, rst_in);  
//* this module define d flip flop with q as output and data, clock and reset as input *//

input d_in, clk_in, rst_in; / input variable of the d flip flop is defined
output reg q; / output variable of the d flip flop is defined

always @ (negedge clk_in) / this block is implemented continuously with every negative edge of the clock pulse

if ( !rst_in) / if else statement
q<= 1’b0;
else
q<=d_in;

endmodule

Verilog Code for D flip flop using Structural Model

/Structural model is used to integrate diffrenet blocks

module nand_gat(co, a, b); / this module defines NAND gate
input a, b; 
output co; 
assign co = ~( a & b); 
endmodule

module not_gat(e, f); / this module defines NOT gate
input f; 
output e; 
assign e= ~f; 
endmodule

module d_ff_strt(q,q_bar,d_in,clk_in); //* this module define d flip flop with q and qbar as output, and data and clock as input *//
input d_in, clk_in; / input variable of the d flip flop is defined
output q, q_bar; / output variable of the d flip flop is defined

not_gat not1 (d_bar, d_in); / here NOT gate module is implemented

/ next NAND gate module is implemented with different parameters 4 times
nand_gat nand1 (x, clk_in, d_in); 
nand_gat nand2 (y, clk_in, d_bar); 
nand_gat nand3 (q, q_bar, y); 
nand_gat nand4 (q_bar, q, x); 

endmodule

Verilog Code for Ring Counter using D flip flop

module dffc (q_in, d_in, clk_in); / d flip flop module is defined
output reg q_o;
input d_in,c_in;
initial
q_o=1'b1;

always@(posedge clk_in) / sensitivity is positive edge of the clock pulse
q_o = d_in;
endmodule

module ring_counterdff (q_o, clk_in); / ring counter module is defined with d flip flop
inout [3:0]q_o;
input clk_in;

/ d flip flop module is implemented with different parameters 4 times
dffc df1(q_o[0], q_o[3], clk_in);
dffc df2(q_o[1], q_o[0], clk_in);
dffc df3(q_o[2], q_o[1], clk_in);
dffc df4(q_o[3], q_o[2], clk_in);
endmodule

Verilog Code for T flip flop using D flip flop

module T_ff(q, t_in, clk_in, rst_in); / this module define T flip flop 

input t_in, clk_in, rst_in; / input variable of the t flip flop is defined
output q; / output variable of the t flip flop is defined

always @ (posedge clk_in) / sensitivity of this block is positive edge of the clock pulse
if(rst_in)
t_in<=t_in^q;
endmodule

D flip flop Verilog Code with Testbench

//* following code is the test bench for a d flip flop is does not have any input or the output as variable, it's purposes is of exercising and verifying the functional correctness of the hardware model *//
module d_flipflopt_b;

reg d_in;
reg clk_in;
wire q;

d_flipflop_mod uut (.q(q),.d_in(d_in), .clk_in(clk_in) );
initial begin
d_in = 0;
clk_in = 0;
end

always #3 clk_in=~clk_in;
always #5 d_in=~d_in;
initial                     #100 $stop;

endmodule

Master Slave D flip flop Verilog Code

module M_slave(d_in, reset_in,clk_in, q ,q_bar);/ this module define the master slave of d flip flop
 input d_in, clk_in ,reset_in;
 output q, q_bar; 
 Master Maste_r(d_in, reset_in, clk_in, qn, q_barn); / implementing master d flip flop module 
 Master Slav_e(q_n,reset_in,!clk_in,q, q_bar); / implementing slave d flip flop module
endmodule

module Master(d_in, reset_in, clk_in, q_in, q_bar); / this module defines d flip flop
 input d_in, reset_in, clk_in;
 output reg q, q_bar;
 initial
  q = 0;
 
always @(posedge clk_in) begin
  if (~reset_in) begin
   q <= d_in;
   q_bar <= !d_in;
  end
  
else begin
   q <= 1'bx;
   q_bar <= 1'bx;
 end

 end

endmodule

JK flip flop using D flip flop Verilog Code

module D_flip_flopf (input D_in ,clk_in ,Reset_in, enable_in,  output reg Fo); / this module define D flip flop
    always @(posedge clk_in) begin
        if (Reset_in)
            Fo <= 1'b0;
        else if (enable) 
            Fo <= D_in;
    end 
endmodule

module JK_flip_flopf (input J_in, K_in ,clk_in, Reset_in, enable_in, output Q); / this module defines JK flip flop
    wire S_1,S_2,S_3,S_4,S_5;
    D_flip_flopf D1(S_4, clk_in, Reset_in,enable_in, Q );

    not N2(S_5, Q);
    and A1(S_1, J_in ,S_5);
    not N1(S_3, K_in);
    and A2(S_2,S_3,Q);
    or O1(S_4,S_1,S_2);
endmodule

Frequency Divider using D flip flop Verilog Code

module freq_div_by2 (clk_out, clk_in, reset_in); //* this module defines frequency divider which can devide the frequency by 2 *//
input clk_in, reset_in;
output reg clk_out;
always @ (posedge clk_in)
if(reset_in)
clk_out<=0;
else clk_out<=~clk_out;
endmodule
FRQ DIV D FF edited
fig. Block diagram of the frequency divider circuit designed with D flip flop.

D flip flop Verilog Code Gate Level

module dffgate(D_in, CLK_in, Q ,Q_n);
    input D_in, CLK_in;
    output Q, Q_n;
    reg Q, Q_n, Ro, So;

always @(negedge CLK_in) begin
    Ro = ~(~(~(D_in|So)|Ro)|CLK_in);
    So = ~(~(D_in|So)|Ro|CLK_in); 
    Q = ~(Ro|Q_n);
    Q_n = ~(So|Q);
end
endmodule

Image Credit : “Binary code” by Christiaan Colen is licensed under CC BY-SA 2.0

VHDL Code for D flip flop

library ieee;
use ieee.std_logic_1164.all;

entity d_flip_flop is 
port (d_in, clk_in: in std_logic; q, q_bar: out std_logic);
end d_flip_flop;

architecture beh_v of d_flip _flop is 
signal qn, q_barn: std_logic;
begin
Process (d_in, clk_in)
begin
If (clk_in’ event and clk_in = ‘1’)
then qn <=d_in;
end if;
End process;
q<=qn;
q_bar<=not (qn);
end beh_v;

VHDL Code for D flip flop using Dataflow Modelling

library ieee;
use ieee.std_logic_1164.all;
use ieee.std_logic_arith.all;
use ieee.std_logic_unsigned.all;

entity d_flip_flop is 
port (d_in, clk_in: in std_logic; q_in, q_out: inout std_logic);
end d_flip_flop;

architecture data_f of d_flip_flop is
signal d_1, s_1, r_1: std_logic;
begin
s_1 <= d_in nand clk_in;
d_1 <= d_in nand d_in;
r_1 <= d_1 nand clk_in;
q_in <= s_1 nand q_out;
q_out <= r_1 nand q_in;
end data_f;

VHDL Code for D flip flop using Structural Model

library ieee;
use ieee.std_logic_1164.all;
use ieee.std_logic_arith.all;
use ieee.std_logic_unsigned.all;
entity d_f _f_st is 
port (d_in, clk_in: in std_logic; q_in, q_out: inout std_logic);
end d_f_f_st;

architecture d_ff_s of d_f_f_st is
component nand_1
port (a, b : in std_logic; c : out std_logic);
begin

n_0: nand_1 port map(d_in, clk_in, s_1);
n_1: nand_1 port map(d_in, d_in, d_1);
n_2: nand_1 port map(d_1, clk_in, r_1);
n_3: nand_1 port map(s_1, q_out, q_in);
n_4: nand_1 port map(r_1, q_in, q_out);
end d_ff_s;

library ieee;
use ieee.std_logic_1164.all;
use ieee.std_logic_arith.all;
use ieee.std_logic_unsigned.all;

entity nand_1 is
port (a, b: in std_logic; c: out std_logic);
end nand_1;

architecture beha_v of nand 1 is 
begin
c<= a nand b;
end beha_v;

D flip flop Behavioral VHDL code

library ieee;
use ieee.std_logic_1164.all;
use ieee.std_logic_arith.all;
use ieee.std_logic_unsigned.all;

entity d_flip_flop_bh is
port (d_in, clk_in, rst_in: in std_logic; q_in, q_out: out std_logic);
end d_flipflop_bh;

architecture beh_v of d_flip_flop_bh is 
begin
process(d_in, clk_in, rst_in)
begin
If (rst_in = ‘1’) then q_in <= ‘0’;
else if (rising_edge(clk_in)) then q_in <= d_in;
q_out<= not d_in;
end if;
end process;
end beh_v;

VHDL Code for D flip flop with Asynchronous Reset

library ieee;
use ieee.std_logic_1164.all;

entity d_ff_asy_rst is
port (d_in, clk_in, reset_in: in std_logic; q_out: out std_logic);
end d_ff_asy_rst;

architecture beha_v of d_ff_asy_rest is 
begin
if (reset_in = ‘0’) then q_out<=’0’;
elseif (clk_in’ event and clk_in= ‘1’)
then
q_out<=d_in;
end if;
end process;
end beha_v;

VHDL Code for D flip flop with Synchronous Reset

library ieee;
use ieee.std_logic_1164.all;

entity d_syn_reset
port( d_in, reset_in, clk_in: in std_logic; q_out: out std_logic);
end d_syn_reset;

architecture beha_v of d_syn_reset is
begin
process
begin
wait until (clk_in’ event and clk_in =’1’)
if reset_in = ‘0’ then q_out<=’0’;
else
q_out<= d_in;
end if;
end process;
end beha_v;

VHDL Code for Negative Edge Triggered D flip flop

library ieee;
use ieee.std_logic_1164.all;

entity d_ff_neg is
port (d_in, clk_in: in std_logic; q_out: out std_logic);
end d_ff_neg;

architecture beha_v of d_ff_neg is
begin process (clk_in) begin
if (clk_in’ event and clk_in = ‘0’) then
q_out<= d_in;
end if;
end process;
end beha_v; 

Test Bench for D flip flop in VHDL

library ieee;
use ieee.std_logic_1164.all;

entity d_flip_flop_test is
end d_flip_flop_test;

architecture behaviour of d_flip_flop_test is
component d_flip_flop_test
port( d_in: in std_logic; clk_in : in std_logic; rst_in: in std_logic; d_out: out std_logic);
end component;
signal d_in: std_logic:= ‘0’;
signal clk_in : std_logic:= ‘0’;
signal rst_in: std_logic:= ‘1’;
signal d_out: std_logic;
constant clk_p: time:=20ns;
begin 
uut: d_flip_flop_test
port map(d_in=>d_in; clk_in => clk_in; rst_in=> rst_in; d_out=> d_out);
clk_p: process begin
clk_in<=10;
wait for clk_p/2;
clk_in<=’1’;
wait for clk_p/2;
end process;
sti_prc: process
begin
rst_in<=’1’;
wait for 50 ns;
rst_in<= ‘0’;
d_in <= ‘0’;
wait for 50ns;
rst_in<=’0’;
d_in<= ‘1’;
wait;
end process;
end;

4 bit Shift Register using D flip flop VHDL Code

library ieee;
use ieee.std_logic_1164.all;
 
entity p_I_p_o is
 port(
 Clk_in: in std_logic;
 D_in: in std_logic_vector(3 downto 0);
 Q_1: out std_logic_vector(3 downto 0)
 );
end p_I_p_o;

architecture archi of p_I_p_o is
begin
 process (clk)
 begin
 if (CLK_in'event and CLK_in='1') then
 Q_1 <= D_in;
 end if;
 end process;
end archi;

VHDL Code for 8 bit Register using D flip flop

library ieee;
use ieee.std_logic_1164.all;

entity reg_sip_o is
port (clk_in, clear : in std_logic; input_d : in std_logic; q: out std_logic vector (7 downto 0 ) );
end reg_sip_o;

architecture arch of reg_sip_o is 
begin
process (clk_in)
If clear = ‘1’ then 
q<= “00000000”;
 elseif (clk_in’ event and clk_in = ’1’ ) then
q(7 downto 1)<= q(2 downto 0);
q(0)<= input_d;
end if;
end process;
end arch;

VHDL Code for Asynchronous Counter using D flip flop

//*following is the VHDl code for a asynchoronous counter designed with d flip flop *//
library ieee;
use ieee.std_logic_1164.all;

entity dff1 is
port (d_in, clk_in ,clr_in : in std_logic; q, q_bar : inout std_logic);
end dff1;

architecture my_dffbharch of dffl is
begin
process (d_in, clk_in, clr_in)
begin
if (clr_in  = '1') then
if (clk_in  = '1') AND (clk_in'EVENT)  then
q <= d_in;
q_bar <= not (d_in);
end if;
else
q <= '0';
q_bar <= '1';
end if;
end process;
end my_dffbharch;

library IEEE;
use IEEE.STD_LOGIC_1164.ALL;

entity dcoun is
port(clk_in, clr_in :in std_logic;
q, q_b:inout std_logic_vector(3 downto 0));
end dcoun;

architecture arch of dcoun is
component dff1 is
port(d_in, clk_in, clr_in :in std_logic;
qi, q_bar:out std_logic);
end component;
signal k ,p , m :std_logic;
begin
k<=qi (0);
p<=qi (1);
m<=qi (2);
a1:dff1 port map('1','1', rst_in, clk_in , qi(0),q_b(0));
a2:dff1 port map('1','1', rst_in,k,q(1),q_b(1));
a3:dff1 port map('1','1', rst_in, p, qi(2), q_b(2));
a4:dff1 port map('1','1', rst_in, m,qi(3), q_b(3));
end arch;

What is a Power Triangle: 23 Facts You Should Know

Power trinagle 300x200 1

The triangle of power | Power voltage current triangle

A power triangle is simply a rightangle triangle with side representing active power, reactive power, and apparent power. The base component symbolizes active power, the perpendicular component denotes reactive power, and the hypotenuse symbolizes apparent power.

What is power triangle?

Define power triangle | Power triangle definition

A power triangle is the graphical presentation of real or active power, reactive power, and apparent power in a right-angled triangle.

Power triangle equation | PQS power triangle

Power triangle

Power triangle formula calculation | Power triangle equation

In a power triangle, active power P, reactive power Q, and apparent power S form a right-angled triangle. Therefore,

hypotenuse2 = base2 + perpendicular2

S2 = P2 + Q2

Here, Apparent power(S) is measured in Volt-Ampere(VA).

Active power(P) is measured in Watt(W).

Reactive power(Q) is measured in Volt-Ampere reactive(VAR).

  • A power triangle is the graphical presentation of real or active power, reactive power, and apparent power in a right-angled triangle.
  • Active or true power refers to the entire amount of power dissipated in an electrical circuit. It is measured in Watt (W) or KiloWatt (KW) and represented with P and average value of the active power P.
  • Reactive power or imaginary power is the power that doesn’t do any real work and causes zero power dissipation. T is also known as watt-less power. This is the power derived from reactive elements like the inductive load and the capacitive load. The reactive power is calculated in KiloVolt Amp reactive (KVAR) and is denoted by Q.
  • The total power in the circuit, both absorbed and dissipated, is known as apparent power. The apparent power is computed by multiplying the r.m.s voltage with r.m.s current without any phase angle quantity.
  • Ohm’s Law always works with DC circuits, but in the case of AC, it only works when the circuit is purely resistive, i.e., the circuit doesn’t have any inductive or capacitive load. But, most of the AC circuits consist of a series or parallel combination of RLC. Due to this, voltage and current become out of phase, and a complex quantity is introduced.
  • The power of the three-phase system is = √3 x power factor x voltage x current.

Power triangle for RLC series circuit | Power triangle circuits

RLC

Let us consider an RLC circuit connected in series as above.

Where, a resistor with resistance R.

 an inductor with inductance L.

a capacitor with capacitance C.

An AC voltage source Vmsin⍵t is applied.

V is the r.m.s value of applied voltage, and I is the r.m.s value of the total current in the circuit. The inductor and the capacitor produce XL and XC oppositions, respectively, in the circuit. Now, there can be three cases-

Case 1: XL > XC

Case 2: XL < XC

The power triangle is obtained from the phasor diagram, if we multiply each of the voltage phasors with I, we get three power components.

Phasor

From the phasor triangle, we can quickly get the power triangle by multiplying the voltages with I. The real power is multiplied by VR, which is equal to I2R. The reactive power is I multiplied by (VC – VL), which is equal to I2(XC – XL). The apparent power V = I2Z is calculated from the active power and the reactive power for both cases, Here we take into consideration another quantity, the complex power. The complex power is the summation of the active power and the reactive power represented in complex form, i.e., with the ‘j’ quantity.

Therefore, complex power

S = P – jQ  when XL < XC

S = P + jQ when XL > XC

Now, for case 1, inductive reactance is less than capacitive reactance. Therefore, reactive power is negative, and angle ϕ is also negative. For case 2, inductive reactance value is more than capacitive reactance value, reactive power is +ve, and angle ϕ is also +ve.

Active reactive apparent power triangle | Power volts amps triangle

Active power and reactive power triangle.

True power triangle.

Active or true power refers to the entire amount of power dissipated in an electrical circuit. It is measured in Watt (W) or KiloWatt (KW) and represented with P and average value of the active power P is,

P = VI = I2R

Reactive power triangle

Reactive power or imaginary power is the power that doesn’t do any real work and causes zero power dissipation. Itt is also known as watt-less power. This is the power derived from reactive elements like the inductive load and the capacitive load. The reactive power is calculated in Kilovolt Amp reactive (KVAR) and is denoted by Q.

Reactive power Q = VIreactive = I2X.

Apparent power triangle

The total power in the circuit, both absorbed and dissipated, is known as apparent power. The apparent power is computed by multiplying the r.m.s voltage with r.m.s current without any phase angle quantity.

Apparent power

CodeCogsEqn 27

For a purely resistive circuit, there’s no reactive power. So, the apparent power is equal to active or true power.

Power triangle for AC circuit | Electrical power triangle

AC circuits can have any combination of R, L, and C and if we want to calculate the total power correctly, we have to know the phase-diff among the I and V. The waveform of the current and the voltage are sinusoidal. As the power = voltage x current, maximum power is obtained when both the waveforms coincide. In this situation, the waveform are called ‘in-phase’ with each other.

  • In a purely resistive AC circuitry, the I and V perfectly align with each other in terms of phase. Therefore just by multiplying them, we can get the power.
  • If the circuit has any inductive or capacitive load, a phase difference is created. Even if the phase difference is minute, AC power is divided into two parts- one positive and one negative. The negative power is not a mathematically negative quantity; it just implies that the power is provided to the system, but no energy transfer takes place. This power is known as reactive power. The positive quantity does some real work, so it is classified as real or active power.
  • Another portion of power is provided to the circuit from the source. It is known as apparent power. The apparent power is calculated by multiplying the r.m.s values of the current and the voltage.

Ohm’s Law power triangle | Ohm’s power triangle

Ohm’s Law always works with DC circuits, but in the case of AC, it only works when the circuit is purely resistive, i.e., the circuit doesn’t have any inductive or capacitive load. But, most of the AC circuits consist of a series or parallel combination of RLC. Due to this, voltage and current become out of phase, and a complex quantity is introduced. We need to apply some special formulas in order to calculate the alternating current and parameters of the power triangle.

Power triangle for capacitive load

A capacitive load means that the power factor is leading as the current lead the voltage by the phase angle.

Power triangle for inductive load

An inductive load represent that the power factor is lagging because the I lags V by the phase angle.

Complex power triangle

Complex power is nothing but the representation of power using complex numbers. The real part represent the active power. Imaginary part represent the reactive power.

Let us assume that the current and the voltage in a capacitive circuit are I and V, respectively. We know, for capacitive load, the I leads the V by a phase angle. Let us take this angle as ϕ.

Let’s say the voltage across the load, V= ve and current I = iej(Ɵ+ϕ).

We know, the power is the voltage multiplied by the current conjugate.

So complex power S = VI* = ve x ie-j(Ɵ+ϕ)= vie-jϕ

S = vi(cosϕ – jsinϕ) = vicosϕ – jvisinϕ = P – jQ [we know active power P = vicosϕ and reactive power Q = visinϕ ]

For the capacitive load, the I lags V by the phaseangle. So, the voltage across the load, V= ve and current I = iej(Ɵ-ϕ).

So complex power

S = VI* = ve x ie-j(Ɵ-ϕ)= vie

S = vi(cosϕ + jsinϕ) = vicosϕ + jvisinϕ = P + jQ

Three-phase power triangle

Alternating current can be single-phase or three-phase. The variation of current amplitude results in the generation of sine waves. For a single-phase supply, there’s just one wave. Three-phase systems split the current into three parts. The three current components are out-of-phase by one-third of a cycle each. Each current component is equal in size but opposite in direction to the another two conjunctive.

The power of the three-phase system is = √3 x power factor x voltage x current.

Impedance triangle and power triangle

Impedance triangle power factor

In DC circuits, only the resistance is responsible for opposing the current. But in AC circuits, a quantity called reactance also opposes the current. The reactance can be any combination of inductance and capacitance. But both the inductance and the capacitance differ from the resistance with a phase angle (lagging or leading). So, we cannot add them arithmetically. So, we construct an impedance triangle with hypotenuse Z(impedance), base R(resistance), and reactance X( inductive or capacitive reactance or both).

CodeCogsEqn 28

Power factor= R/Z

Power triangle power factor

The power factor in the power triangle is referred to as the ratio of active power and apparent power, defined as the cosine of the phasor angle.

Power factor correction triangle

The power factor correction is a method to increase the efficiency of an electrical circuit by reducing the reactive power. Power factor correction is achieved through parallel-connected capacitors that oppose the effects caused by inductive elements and decrease phase shift.

Power factor triangle formula

The power factor for capacitive or inductive load= R/Z

Power factor = Real power/Apparent power

Power energy triangle

Electrical energy is defined as the system’s power multiplied by the total time the power is used.

Energy E = P x T

How to draw a power triangle?

Power triangle generator

The power triangle is constructed by taking the active power as the base, the reactive power as perpendicular, and the apparent power as the hypotenuse.

Metal triangles on power lines

We often see a few triangular loops hanging from the power lines. These are used to provide stability to the lines in high wind. These triangular fins prevent the lines from bouncing too close to each other and ensure that they are not loosened from the insulators.

Electrical power triangle calculations | Power triangle calculator

Q. An inductor coil of 120 mH and a 70 ohm resistance are connected in series with a 220 volt, 50 Hz supply. Calculate the apparent power.

Inductive reactance

CodeCogsEqn 29

Impedance of the inductor

CodeCogsEqn 30

So, the current consumed by the inductor = V/Z= 220/79.5 = 2.77 A

Therefore, phase angle

CodeCogsEqn 31

lagging

Active power

CodeCogsEqn 32

Reactive power

CodeCogsEqn 33

Apparent power

CodeCogsEqn 34

Q. Calculate the power factor of the series RLC circuit with inductive load 23 ohm, capacitive load 18 ohms, and resistive load 12 ohms connected with a 100 volt 60 Hz supply voltage.

Given:

Inductive reactance XL = 23 ohm

Capacitive reactance XC = 18 ohm

Resistance = 12 ohm

Total impedance of the circuit

Power factor of the circuit = R/Z = 12/13 = 0.92

Power triangle example

Q. A load of 20 kW is at a power factor 0.8 lagging. Find the capacitor rating so that it can raise the value of the power factor to 0.95.

Here, the true power P = 20 KW

Power factor cosϕ1 = 0.8

We know, the reactive power must be reduced to get an increased power factor. Therefore, the phase angle will also decrease. Let us assume that initially, the phase angle was ϕ1, and after reducing the reactive power, the phase angle is ϕ2. So, the power triangle looks like-

Example

We can see from the diagram that the reactive power has decreased to AB from AC. So we need to compute the difference of AC and AB, and this quantity is the required capacitor rating.

Here, OA = 20 KW

cosϕ1 = 0.8

cosϕ2 = 0.95

We know, cosϕ1 = OA/OC  

So, OC = 20/0.8 = 25 KVA

AC = √(OC2 – OA2) = 15 KVAR

Cosϕ2 = OA/OB

So, OB = 20/0.95 = 21 KVA

AB = √(OB2 – OA2) = 6.4 KVAR

Therefore, BC = AC – AB = (15 – 6.4) = 8.6 KVAR

FAQs

How many types of powers are there in the power triangle?

The power triangle consists of three types of power

  • – True or active power.
  • – reactive power.
  • – apparent power.

What is power triangle? Explain active,reactive and apparent power with an exemplar.

The power triangle is the triangular representation of the relationship between the true power, the reactive power, and the apparent power.

For example, in any electrical appliance, the total power generated is the parts of the active and the reactive power.

What is the power triangle of an AC circuit?

The power triangle of an AC circuit can be resistive, capacitive, or Inductive and  triangle consists of three kinds of powers, and the apparent power is computed with the help of the active power and the reactive power.

What is the power triangle of an RL circuit?

The RL circuit has a power triangle with the active power = I2R, the reactive power = I2XL, and the apparent power = I2Z, where XL is the Inductive reactance and Z is the total impedance of the circuit.

What is the relation between KVA, KW, & KVAr?

KVA is the unit of the apparent power, whereas KW and KVAR are the units of true power and reactive power, respectively. Therefore from the concept of the power triangle, we can conclude that KVA2 = KW2 + KVAR2.

What is the significance of the power factor?

For inductive and capacitive loads, the power factor plays a vital role in computing the reactive power. Reactive power is the part of active power that gets diminished and powerfactor is the ratio of the true power and the apparent power. The unity power factor indicate that the circuit is completely resistive in nature.

How many watts is 6 KVA?

6 KVA = 6000 VA

At unity power factor 6 KVA = 1 x 6000 = 6000 Watts

If the power factor is anything else, 6 KVA = 6 x (power factor) watts

How to convert KWH to KVAH?

KWH = KVAH X power factor

Therefore, KVAH = KWH/ power factor

How many watts does 1 kVA equal to?

For a purely resistive load, there’s no reactive power. So the power factor is 1. Here 1 kVA= 1 Watt

If the load is capacitive or inductive, the resistive power is not 0, as power factor is resistance/impedance. Here 1 kVA = power factor x 1 KW

Why are electric towers in triangular shapes?

For the following reasons, electric towers are triangular.

  • ‌Triangles have a greater base area which allows them to be highly rigid. This rigidity helps in withstanding side loadings.
  • ‌Triangles have less area than any quadrilateral. If the shape were quadrilateral, then the cost would have been more. The triangular shape reduces the cost by eliminating one extra side.

What is the power factor for a transformer?

The power factor of a transformer depends upon the characteristics of the load.

‌If the load is purely resistive, the power factor is Unity or 1.

‌If the load is capacitive, i.e., XC > XL, the power factor is known as leading.

‌If the load is inductive, i.e., XL > XC, the power factor is known as lagging.

What is the difference between KVA KWH KVAH and KVAR? | Power triangle KW KVA KVAR

KVA stands for Kilo Volt Ampere. This is the unit of real or active power.

KWH stands for Kilo Watt Hour. This is used to measure how much power(in kilowatts) is consumed in an hour.

KVAH stands for Kilo Volt Ampere Hour. KVAH is the apparent power, whereas KWH is the active power. KVAH = KWH/ power factor

KVAR stands for Kilo Volt Ampere reactive. It is used to measure reactive power.

What is the power factor of an L-R circuit?

The impedance of an L-R circuit is Z = R + jωL

We know, power factor

CodeCogsEqn 36
CodeCogsEqn 37

What is the unit of the power factor?

The power factor is the ratio of the active power (KW) and the apparent power (KVA) as both the numerator and the denominator are powers, the power factor is a unit less quantity.

 

Desuperheater: 17 Important Facts You Should Know

Superheated Steam and the Desuperheater 300x200 1

TABLE OF CONTENTS

DESUPERHEATER DEFINITION

Desuperheater is used for carrying out the desuperheating process which is to reduce the temperature of the superheat and to bring back the vapor into a saturated state. A desuperheater performs the role contrary to that of a superheater. In most of the desuperheaters, the temperature of the exit fluid is within 3degrees of the saturation temperature. There are also cases where the discharge temperature is more than 3 degrees of saturation temperature.

Desuperheater
Desuperheater in Industrial Settings (Image Credit: Komax Systems)

In power generation plants, the role of superheat is significant and hence superheaters are highly recommended. When the temperature of the steam is higher than the saturation temperature, then the state of the steam is referred to as superheated. In this state, the liquid and the vapor are not in equilibrium and can be analyzed from the equilibrium charts.

Superheated steam is preferred during the transfer of heat from one source to another because it acts as an insulator while saturated steam is required for heat transfer processes. In power generation processes, there is a need for both heat insulation and heat transfer, and this is respectively carried out using superheating and desuperheating procedures using superheaters and desuperheaters.

The temperature of the superheated steam is lowered using a heat exchanger that uses a coolant to lower the temperature of the superheated steam and is termed as a desuperheater. In most of the desuperheaters, the fluid that is used for lowering the temperature of the superheated steam is the same as it that of the vapor. Water is the fluid used as a coolant in the case of superheated steam.

DESUPERHEATER TYPES

Desuperheaters are mainly of two types i.e., a direct contact type superheater and an indirect contact superheater which are explained in detail below:

1. Indirect contact desuperheater: In this type of desuperheater, the coolant does not come in direct contact with the superheated vapor. Here the coolant employed will be a liquid or a gas which is allowed to flow through one side of the heat exchanger while the superheated steams pass through the other side. The heat from the superheated steam passes into the coolant through the heat exchanger.   

An example of this type of process is the heat exchange between air which is used as a coolant and hot fluid that is passing through the coils where the air does not come in direct contact with the superheated fluid, but the heat is transferred from the fluid to the air through indirect contact or convection mode of heat exchange.

In these types of desuperheaters, the coolant flowrate or the inlet pressure of the superheated steam can be used for controlling the temperature of the desuperheated steam. It is not feasible to control the flow of superheated steam in these types of processes.

2. Direct contact desuperheater: In this type of superheater, the superheated steam comes in direct contact with the coolant. Usually, the coolant that is used for lowering the temperature of the superheated steam is the liquid form of the vapor. Water is used in most cases as a liquid coolant for superheated steam.

In a direct superheater, a measured quantity of coolant is added to the superheater utilizing the mixing process wherein the coolant mixes with the steam. Once it passes through the desuperheater, the coolant leaves or evaporates from the mixture by absorbing heat from the superheated vapor. In this way, the temperature of the superheated steam is lowered.

The amount of coolant to be added to the process is calculated depending on the steam temperature flowing out of the desuperheater. The desuperheater steam temperature would be set above 3 degrees of the saturation temperature. It is essential in such cases, to keep the superheated steam pressure constant.

DESUPERHEATER PIPING DIAGRAM | DESUPERHEATER PIPING

The Ins and Outs of Desuperheaters and the Industries that Benefit 1024x681 1
Desuperheater Piping (Image Credit: Komax Systems)

The desuperheater piping is complex. During the installation of a desuperheater pipeline, the following precautionary measures need to be followed

  • When the same header gives rise to two or more control valves, it should be ensured that there is no instability inflow due to pressure changes.
  • The pipe installed upstream of the control valve should be straight and should have a length 6 times that of the inlet diameter of the pipe body.
  • Downstream to the valve, it is suggested not to rise the piping alignment to avoid the collection of condensates.
  • Further, it is also recommended to protect the temperature probe with insulation where bellows or valves are present.

DESUPERHEATER COILS

Desuperheater coils especially the pack less type has a tube-to-tube design. In this type of design, water flows through the inner tube which has a double wall and the refrigerant flows through the annulus between the tube-to-tube walls. The convoluted structure of the inner tube promotes enhanced heat transfer per unit length and unit area. Further, the convolutions that are offered by the coils promote turbulence which also contributes to the increased thermal efficiency. The rate of heat transfer is enhanced with water and refrigerant in a counterflow arrangement.

DESUPERHEATER BUFFER TANK

In residential apartments or homes, a desuperheater buffer tank is a tank in which the water from the pipeline flows into it enters the water heater. The water is preheated by the desuperheater connected to the buffer tank before it is sent to the water heater. Thereby reducing the load on the water heater.

DESUPERHEATER WORKING PRINCIPLE

Desuperheater or Steam Desuperheater works on the principle of evaporative cooling whereby the liquid water that is sprayed on the superheated steams results in its cooling. On the other hand, the heat absorbed by the liquid coolant helps it in the evaporation process. The heat is obtained from the superheated steam via convection heat transfer. As a result of this process, the steam that comes out from the desuperheater is at a lower temperature.

In a powerplant with a desuperheater, the accumulation of water near the sides of the equipment can occur due to its continuous operation. A hot water spray can be used to remove the water that is accumulated. The hot water spray is maintained at a temperature close to the steam saturation temperature at the exit of the equipment.

STEAM DESUPERHEATER DESIGN

The steam superheater design and sizing are dependent on several requirements with a few being less severe while others having a greater impact on the proper functioning of the desuperheater. To ensure that the desuperheater is performing at an optimal level, the following factors need to be addressed carefully:

1. Ensure that an appropriate amount of cooling is available i.e. ΔTsteam

2. Measure the accurate flow of spray water that is required (Fspray/ Fsteam)

3. Ensure the narrow difference between the steam and saturation temperature (Tsteam – Tsaturation)

4. Fixed range of superheated steam flow rates

5. Fixed range of coolant or water spray flow rates

6. Pressure head of the coolant spray

7. Factors affecting the installation of the desuperheater

These requirements are usually met in applications such as reheat attemperator, bypass process in turbines, and while processing steam for the export. A physical model needs to be in place for the spraying, evaporation, and atomization process of desuperheating. The important rules to be followed for sizing and selection of desuperheater are as follows:

1. It should be ensured that the droplet size is within 250 microns at all operating conditions.

2. The penetration of the spray droplets should be in the range of 15 to 85 percent of the tube diameter. This is to avoid the impingement that can occur. It is a result of cold water hitting the surface of hot bodies or metals or surfaces.

DESUPERHEATER SPRAY NOZZLE DESIGN

A desuperheater spray nozzle helps in controlling the superheat by regulating the cooling water that will be sprayed through the nozzles in the design. It usually consists of a water control valve which helps in attaining a controlled desuperheated flow temperature and negligible pressure drop. The Kv / Cv value and the number of nozzles which is about 6 to 9 will be calculated according to the process conditions.

DESUPERHEATER CONTROL VALVE

Desuperheater is used for carrying out the desuperheating process which is to reduce the temperature of the superheat and to bring back the vapor into a saturated state. A desuperheater control valve helps in controlling the temperature and pressure by adjusting the valve openings depending on the saturation temperature.

DESUPERHEATER REFRIGERATION

In a refrigeration system, the energy from the condensation process of a refrigeration system is left to the ambient environment or discharged to a heat sink. This energy could be used in an effective way for water heating or room heating. To recover the waste heat, the installation of a desuperheater is highly recommended whereby the waste loss can be minimized.

The location of a desuperheater in a refrigeration system is between the compressor and condenser to make use of the energy of the superheated refrigerant. For utilizing the waste heat, a separate heat exchanger should be installed wherein water can be heated using the energy from the superheated gas.

The temperature difference between the discharge from the compressor and the refrigerant condensing temperature will give the available amount of superheat. In case, there is no need for hot water, then this system can be bypassed, and the condenser should have the required condensing power or capability.

Since water is the common fluid that is used in desuperheaters, there are high chances for scaling to take place because as the temperature increases it is difficult to dissolve limestone or calcium carbonate which is the main component of scaling. The allowable temperature of water to limit scaling would be in the range of 65-700C. Further, the use of hard water also increases the chances of scaling. In such cases, it is recommended to use co-current flow to avoid high-temperature risks.

DESUPERHEATER GEOTHERMAL | WATERFURNACE DESUPERHEATER 

A desuperheater which is also termed a water furnace desuperheater or a geothermal desuperheater helps in reducing the costs of water heating and room heating. The excess amount of heat that is absorbed during the summers is used for heating the water. During winter, the heat that is available via a desuperheater is at a much lower cost than a standard domestic water heater.

The heat that is rejected is made use of an in desuperheater hot water superheater. It is recommended to have a buffer tank or a pre-tank which would help in preheating the water.

DESUPERHEATER PUMP

In residential or domestic water heating using desuperheaters, the heat during the summers is used for heating the water. It is essential to have a desuperheater pump that would help in pumping the water to the buffer tanks before it is available for the desuperheating process. During winter, the heat that is available via a desuperheater is at a much lower cost than a standard domestic water heater.

It is essential to note if the sizing of the pump is appropriate for heating purposes. The desuperheater uses the heat energy that is being removed while its main purpose is to cool the room.

DESUPERHEATER COST

The desuperheater cost which can be installed for residential purposes is very much affordable and costs about $1350 approximately. For installing a desuperheater, it is essential to have a heat pump which is included in the total cost that is mentioned. A heat pump with a coefficient of performance of value 4 would help in saving 75% which is a great investment when it comes to the residential or domestic water heater.

DESUPERHEATER AND ATTEMPERATOR

A desuperheater is used for removing the heat that is present in the superheat thereby reducing the temperature of the superheat close to saturation temperature or below. An attemperator is used for regulating the steam temperature of the boiler. A desuperheater is usually located downstream from the boiler where saturated steam would be useful. While an attemperator is allocated close to the boiler where high temperatures could have an impact on the walls or surfaces which would, in turn, have an impact on the process operation.

VENTURI DESUPERHEATER | VENTURI TYPE DESUPERHEATER

Venturi desuperheaters or annual desuperheaters help in reducing the temperature of the superheated steam by bringing it in direct contact with water. Here evaporative cooling takes place. They can be used in different environmental conditions and can be vertically or horizontally installed. When they are vertically installed, there is a substantial increase in the turn-down ratio.

These types of superheaters prevent the accumulation of water, which is not vaporized, which is a major drawback in most of the desuperheaters. Here the droplets of water that fail to vaporize will be sent back to the high-temperature region where they will be completely vaporized.

The advantage of using Venturi desuperheater is that they can be installed either vertical or horizontal. Further, they are built of heavy materials and do not have any moving parts which could interfere with their proper functioning. They are generally used in controlling temperatures of fluid that are sent to the evaporator or used in heat exchangers especially at the entrance to reduce the dimensions and cost.

LNG DESUPERHEATER

In a propane refrigeration system, water is used for condensation of the propane after the compression stage. It is recommended to use two propane desuperheaters which work on the same principle that is to reduce the temperature of the superheated steam. Such a system should also be equipped with 6 propane condensers in parallel orientation. Shell and tube heat exchangers are usually used in this type of system.

FREQUENTLY ASKED INTERVIEW QUESTIONS AND ANSWERS

1. How does a desuperheater work in a boiler? | Function of desuperheater in a boiler

Desuperheaters are used in boilers to reduce the temperature of the superheated steam that is produced in the superheater for electricity generation. The desuperheater helps in lowering the high temperature of the steam to low temperatures that will help in safely carryout the other process operation. The temperature of the superheated steam is controlled by bringing the steam in direct or indirect contact with a coolant. The injected water is then allowed to evaporate.

The two main reasons for lower the steam temperature are as follows:

1. The downstream equipment is designed to handle lower temperatures hence it is essential to lower the temperature of the steam.

2. To ensure that a controlled temperature is maintained for processes that required a specific temperature.

2. Why is a steam desuperheater installed after a turbine and what is the function of a surface condenser installed after it?

A steam desuperheater is used for lowering the temperature of superheat by bringing the superheat in direct or indirect contact with a coolant.

The superheated steam loses some of its heat in the turbine though not all of it. The remaining superheat which when exposed to a lower pressure results in entrained droplets of water flashing into steam which causes water hammer and other conditions.

The job is completed using the surface condenser which removes all the steam from the entry point and below the saturation so that the steam is condensed can be used for other purposes which include recycling to the boiler or other load extraction processes.

3. How is desuperheating of steam in superheaters and reheaters in a steam power plant considered a loss inefficiency?

In a desuperheater, the heat from the steam is not being used and contributes as waste heat which needs to be recovered through integrated systems. Further, the steam temperature at the outlet of the desuperheater is lower than before. Hence, this results in a loss of efficiency.

For systems with reheating, the heat that is obtained from coal or any other fuel is always less than the heat that is available for the steam. A reheater can never attain 100% efficiency. As a result, the available efficiency will be multiplied by the actual efficiency and this will lower the efficiency value.

4. How much water is required to desuperheat steam?

The amount of water required in a desuperheater depends on the amount of superheat or degrees of temperature that need to be lowered and depends on the pressure of the steam header. It can be calculated using an enthalpy balance whereby the summation of the enthalpy of steam and water is equal to the heat that is present in the exit stream. For carrying out this calculation, a steam chart would be handy.

Since the heat capacity of steam and the heat of vaporization is noted to be 0.5BTU/lbf and 1000 BTU/lbf respectively, the amount of water that is required for desuperheating would be less than the amount that one would guess. The water that is used for desuperheating should be demineralized to avoid solid build-up in the desuperheater.

In short, the amount of water required for desuperheating superheated steam depends on the temperature of the steam and the degrees of temperature to be lowered.

5. How does a pressure-reducing desuperheating system work in a thermal power plant?

In a pressure-reducing desuperheating system which is also known as a PRDS system, the required steam quality of specific quantity, temperature and pressure is released. The steam that is used in this system is either fresh steam or steam that is bled. This process is carried out using attemperating water that is obtained from the condensate water. The two fluids are mixed at controlled measures to obtain the steam at specific pressure and temperature.

6. What keeps a superheater from being damaged by heat before a boiler makes steam?

The reason why the superheater is not affected by the heat is that the steam that flows through the superheater cools the metal surfaces and other parts thereby reducing damages to the superheater.

7. What is the maximum velocity of water through the spray nozzle for the desuperheater?

The maximum velocity of water through the nozzle is about 46 to 76 meters per second. The turbulence is noted to be low when the minimum velocity of water is low, such that droplets of water get suspended from the steam and fall out.

8. Desuperheater Energy Balance

It can be calculated using an enthalpy balance whereby the summation of the enthalpy of steam and water is equal to the heat that is present in the exit stream. For carrying out this calculation, a steam chart would be handy.

Hsteam + Hwater = Qexit stream

9. what is the use of a desuperheater in a superheater?

Desuperheaters are used in boilers to reduce the temperature of the superheated steam that is produced in the superheater for electricity generation. The desuperheater helps in lowering the high temperature of the steam to low temperatures that will help in safely carryout the other process operation.

10. Turn off desuperheater in winter

It is recommended to turn off the desuperheater during the winter because there are chances of absorbing heat from the pipeline carrying hot water, thereby reducing the efficiency of the system to heat the house during the winters.

To have a better understanding of Desuperheaters, it is recommended to read on Superheaters

Kelvin 4 Wire Resistance Measurement: 11 Important Facts

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The Subject of Discussion: Kelvin 4 Wire Resistance Measurement:

What is 4 Wire Resistance Measurement ?

4 Wire Resistance Measurement

There are different methods to measure different types of resistance, where varies with the range of resistance. 4 wire resistance measurement method is a very accurate measurement method, which can measure very low resistance with high accuracy. It is used to avoid contact resistance or lead wire resistance problems in the circuit. Here every connection wire is called kelvin connection.

In 4 wire resistance measurement method, the four-wire connection is used where two-wire is used to deliver the supply current to the measuring component, and another two-wire is used to measure the voltage drop across the measuring element.

As we know, at constant temperature Ohm’s law define resistance ‘R’ as the ratio of voltage across the resistance to the current ‘I’ passing thru it, So with measuring the voltage drop across the measuring component with known current passing through it, the resistance of the measuring element can be calculated.

What is Kelvin Bridge ?

Kelvin Bridge

The basic principle of the Kelvin 4 wire resistance measurement is based on Kelvin Bridge. Kelvin Bridge is a modified version of the Wheatstone bridge used to measure the very low resistance value, which ranges from 1 ohm to 0.00001 ohms. In this bridge, the effect of load resistance contact resistance and the resistance of the lead wires are taken into account.

Kelvin Bridge Circuit:

circuit 3
Fig. Kelvin Bridge circuit.

Yb in the figure is the connecting lead wire Resistance.

Whenever the galvanometer is connected to point ‘a’, then the resistance of the connected lead is summed up to the resistance Rx and total impacts become Rx + R{ab} + R{cb}.

Whenever the meter is attached  to point ’c’ the resistance of the lead wires  summed up to R3 + R{ab} + R{cb}.

And when the galvanometer is attached to the point ‘b’, which is between ‘a’ and ‘c’ point, in such a way that the ratio of lead resistance from ‘a’ to ‘b’ and ‘c’ to ‘b’ is the same as the ratio of R1 to R2.

Equation 1 :

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Now the overall equation of the circuit become

Equation 2 :

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From equation 1 and 2 after solving we get :

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The final equation is the same as the balanced Wheatstone Bridge, which shows that connecting lead wire has been eliminated by connecting the galvanometer at point ‘b’. Yb is eliminated with the kelvin bridge.

Kelvin 4 Wire Resistance Measurement has been described in this article with important concepts .
4 Wire Resistance Measurement Circuit elaborated.
Advantages and Disadvantages of Kelvin 4 Wire Resistance Measurements described.
Difference between 4 Wire vs 2 Wire Resistance Measurement represented.
Important Applications of 4 Wire Resistance Measurement has been described.

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What is 4 Wire Resistance Measurement ?

4 Wire Resistance Measurement Method | 4 Wire Resistance Measurement Technique

When measuring low resistance, the connecting wires can cause an error in the result of measurement. If the error produced is higher than the tolerance, or if the accuracy of the measurement is required very high degree, then four-wire resistance measurement is used. Ideally, the wire does not have any internal resistance, but in practice, every wire has some internal resistance.

4 Wire Resistance Measurement Circuit:

In the 4 wire resistance measurement method, 4 wire connection is used where two-wire is used to deliver the measurement current to the measuring component, and another two-wire is used to measure the voltage drop across the measuring component.

kelvin 4 wire resistance measurement
Fig. 4 wire resistance measurement circuit.

In this 4 wire resistance measurement method fixed current generator is used. So if the resistance through the circuit varies, the fixed current generator will supply a constant current through the circuit.

The wire which is used in voltage measurement is connected straight to the legs of the resistance, which is to be measured, and the voltage metre is used in this method is of high impedance so that minimal current passes through it. With a small current through the wire, the overall voltage drop across the wire is negligible, which doesn’t affect the value of the measuring component voltage drop. This method eliminates the wire resistance, which is also called Kelvin or four-wire method. Hear special connecting clips are used, which is known as Kelvin clips.

Kelvin Clip Circuit Connection:

circuit 4
Fig. Kelvin Clip used in the circuit connection.

Kelvin clips are also known as alligator or crocodile clips. Each half of the jaw of a Kelvin clip is insulated from one another; both Jaws of the Kelvin clip are electrically common to each other, which usually joint at the high point. The current delivering wire is connected to one jaw, and the voltage measuring wire is linked to the other jaw. Kelvin Clips are used when the accuracy of the measurement is required high.

What are the Applications of 4 Wire Resistance Measurement ?

4 Wire Resistance Measurement Application:

  • Remote Sensing.
  • Resistance thermometer detector.
  • Induction hardening.

What are the main Disadvantages of  4 Wire Resistance Measurements ?

Disadvantages of Kelvin 4 Wire Resistance Measurements:

  • Expensive.
  • Complicated circuit.
  • Testing speed is very slow.
  • The no. of test points is twice.
  • Larger number of connection wires are required.

2 Wire and 4 wire Resistance Measurement

In the 2 wire resistance measurement, the total lead wire resistance adds to the measurement because the current through the whole circuit is the same. As the voltage drop through the wire and the measuring component can produce a measurement with error, It does not have a very accurate output for a small value of resistance when the measuring resistance is much larger than the wire resistance. Then the lead resistance can get negligible. If the length of the wire can be minimum as possible, then the measurement’s accuracy can be increased.

circuit 1 1
Fig. Two wire resistance measurement connection.

As we can see from the above figure, RW1 and RW2 are the lead wire resistance. This is because the Voltmeter measures the voltage drop across R + RW1 + RW2 . 2 wire resistance measurement is a less accurate simple circuit structure, requiring fewer connecting wires.

3 Wire Resistance Measurement

3 wire resistance measurement, which is not accurate as 4 wire resistance measurement, is more accurate than two-wire resistance measurement. The complexity of the circuit is less than that of 4 wire resistance measurement.

circuit 2
Fig. 3 wire resistance measurement circuit.

In this method, the switch is used, so at first, the upper loop of the resistance is measured, the Voltmeter measures the voltage across RW1 + RW2, then divide the value by 2, which gives the average resistance of these two wires. RW3 is assumed to be the same as the avg. of RW1 and RW2.

Then, switch the circuit to the regular connection, which measures the measuring component and the resistance of wire RW2 + RW3. The calculated value across ( R + RW2 + RW3) then compared with the first measured value

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which is used to eliminate the lead resistance produced by the wire from the measured value.

3 wire resistance measurement connection can be very accurate if all the three wires connected are of the same resistance value R1 = R2 = R3. 3 wire resistance measurement is widely used in industrial applications, which offers good compromise; it is accurate and uses less wire than 4 wire resistance measurement.

4 Wire Resistance Measurement Vs 2 Wire | 2 Wire Vs 4 Wire Resistance Measurement | 4 Wire vs 2 Wire Resistance Measurement

Parameter4 Wire Resistance Measurement2 Wire Resistance Measurement
Connecting wire4 connection wire2 connecting wire
AccuracyVery high even for low resistance measurement.Very low for low resistance measurement.
Used for range of the resistanceUnder 1-ohm resistance1 ohm to 1 kilo ohm
Circuit designComplexSimple
CostExpensiveCheap
Table: comparison between kelvin 2 wire and kelvin 4 wire resistance measurement

Frequently Asked Questions

What is actual working of 2 wire 3 wire and 4 wire types of resistance temperature detector i e RTD ?

RTD stands for resistance temperature detector. It is known that the resistance of a metal changes with the temperature change, so by measuring the resistance with the temperature change, the temperature difference can be detected. They are some metals where the temperature Coefficient is positive, so with the increase in temperature, the electrical resistance of metal increases. RTD can use 2 wire, 3 wire or 4 wire method.

The error introduced by the lead can cause a significant error, so there are very few applications of 2 wire RTD, 2 wire RTD is used with short lead wire or where high accuracy is not needed. Three-wire RTD measurement circuit that minimises the effect of lead wire resistance as long as the connecting wires are of the same length. Some factors such as terminal corrosion or loose connection can still significantly differentiate the lead resistance.

Three-wire RTD is more accurate than two-wire RTD, whereas less accurate than 4 wire RTD, where three-wire RTD is commonly used in the industry relatively cheaper than that of four wires and has a more straightforward Circuit Design than that of a four-wire RTD. In 4-wire resistance measuring, RTD is where the lead wire resistance can be observed and separate from the sensor measurement 4-wire RTD is a true 4 wire resistance measuring Bridge 4-wire RTD is used where high accuracy is needed. Still, it is very expensive and complex in design.

What are the disadvantages of the method of measuring resistance of a wire utilizing an ammeter and a voltmeter in a circuitry ?

Disadvantages depend upon the circuitry’s design, which will measure the resistance for two-wire resistance measurement accuracy is low and for four-wire resistance measurement accuracy is high. In contrast, the two-wire measurement circuit is very simple and cheap, whereas 4 wire resistance measurement is complex and expensive.

The disadvantage of measuring resistance using an ammeter and Voltmeter can be using meters that are not working correctly. The range of the measurement should be considered for the selection of meters, other disadvantage voltmeter and ammeter should be connected to the circuit in different branches. The Voltmeter should be connected parallel to the measuring load, where the ammeter should be connected in series with the branch where the current is to be measured.

To know more about mutual inductance click here

What is the resistance of an electric heater?

According to Joule heating or Ohm heating, heat is proportional to resistance. Joule heating is a process by which electric current passes through a conductor produces heat, so for an electric heater, there must be high resistance in the wire.

What are the factors affecting the resistance?

  • Temperature
  • Length of the wire area
  • Cross-section area the wire
  • Nature of material

Will a thick wire have more resistance than a thin wire Why ?

The thin wire usually have greater resistance than a thick wire because the thin wire has fewer electrons to carry the current and In comparison, the thick wire has more electrons to carry the current. In addition, the relation of resistance and area of cross section of a wire is reciprocally proportionate, because of this if cross section of a wire reduce, the value of wire’s resistance will be higher.

How to increase the resistance of a wire ?

The increase in length of the wire or decrease in the area of the cross-section of a wire increases the resistance.

What is the cross sectional area of a wire?

If we cut a wire vertically perpendicular to its length, then we get a circle face of the wire. The area of the circle face of the wire is known as the cross sectional area of the wire and this area of a wire does not depend upon the length of the wire, and it is generally uniform throughout the entire length of the wire.

Why use a high impedance voltmeter ?

Ideal Voltmeter has an infinite impedance that does not consume any current from the circuit. Still, practically e infinite impedance is not possible. A high impedance voltmeter is used. The current that passes through the Voltmeter is very small, so it does not affect the overall circuit.

Is temperature is directly proportional to resistance ? 

The temperature is directly proportional to resistance for a metal conductor or the metal with a positive temperature coefficient.

What are the effects of temperature on resistance?

The effect of temperature on resistance depends on the temp co-efficient of the resistance. This can be defined as the change in resistance per unit change in temperature,if co-efficient is positive, resistance will increase with the temperature rise and if Co-efficient is negative, resistance will decrease with the temperature rise.

Can a wire have zero resistance?

Ideally, zero wire resistance is possible, but practically, no wire present has zero resistance.

Why do we use three-wire RTD?

Three-wire RTD is most accurate when connecting lead wire resistance to three-wire RTD is cheaper than a four-wire RTD and has a less complicated Circuit Design than a four-wire RTD.

What is the benefit of a four-wire resistance measurement?

Four wire resistance measurements can eliminate the lead wire resistance and have resistance measurement having the highest accuracy.

Link to latest article

Forming Process: 31 Important Factors Related To It

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Forming is type of manufacturing process used very widely through out the world and is one of the old technique. Following are the points we are going discuss in detail in this article:

Content

What is forming? | Fundamentals of metal forming processes

Forming/ Metal forming is a process in which material deforms plastically to get the required shape by application of force in such a way that the stress generated should be greater or equal to yield stress, and simultaneously, it should be less than the ultimate stress of the material.

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Types of forming process | Forming process in manufacturing | Bulk metal forming processes | Metal forming processes | Forming operations | Type of forming operations | Different types of forming | | Classification of metal forming process | Types of plastic forming

Metal forming:

1) Bulk metal forming: 

  1. Forging
  2. Rolling
  3. Extrusion 
  4. Wire forming

2) Sheet metal forming

  1. Bending
  2. Deep cup drawing
  3. Shearing
  4. Stretching
  5. Spinning

3) Advanced metal forming

  1. Super plastic forming
  2. Electroforming
  3. Fine and banking operation
  4. Hydro forming
  5. Laser forming
  6. Powder forming

Microstructure evolution in metal forming processes

When metal forming is carried out, the material goes under very high stress to change it shape. The microstructural change in the material take place. But the formation of crystals will only re arrange if it is hot work, that is worked above recrystallization temperatre. That is the material is heated above its recrystallization temperature and forming is carried out.

Temperature in forming processes | Hot metal forming processes | Cold metal forming processes | Effect of temperature on metal forming process

  • Temperature stands to be a very important factor in the manufacturing process, as the material properties are a function of the temperature.
  • The working in forming process is divided into three parts on basics of temperature:
  • 1. Cold working
  • 2. Warm working
  • 3. Hot working
  • Before defining the above points, let us know what Recrystallization temperature is.

Recrystallization temperature:

  • The temperature at which the material will reform the arrangement of its crystal is known as recrystallization temperature.
  • It is unique value for each material
  •  Lead, Tin, Zinc, and Cadmium is the material whose recrystallization temperature is equal to the room temperature and hence work perform on this materials is always hot work.
  • Recrystallization temperature ranges from 0.5 to 0.9 times of melting temperature of the material.

Cold working:

  • When work is done on the material, when material’s temperature is below the Recrystallization temperature, such work comes under the category of cold working.
  • The amount of force and energy required in cold working is very high.
  • The accuracy is quite good in cold working as compared to others.
  • Properties like Strength and Hardness increase. 
  • While the properties like malleability and ductility reduce.
  • Friction acting in cold working is low.

Warm-working:

  • When work is done on the material at a temperature above cold working but less than the recrystallization temperature, it comes under the category of warm working.
  • It is preferred over cold working when the amount of force applied is less.

Hot working:

  • When work is done on the material, material’s temperature is greater than the Recrystallization temperature, such work comes under the category of hot working.
  • The amount of force and energy required in hot working is less.
  • The accuracy maintains poor in hot working as compared to others.
  • Properties like Strength and Hardness decrease.
  • While the properties like malleability and ductility increase.
  • Friction acting in hot working is high.

Types of cold forming process

Cold forming techniques: squeezing process, bending process, drawing process, and shearing process. 

Squeezing process consist of:

  • Rolling process,
  • Extrusion process,
  • Forging process,
  • Sizing process

Bending process consist of:

  • Angle bending process,
  • Roll bending process,
  • Roll forming process,
  • Seaming process,
  • Straightening process
  • Shearing process consist of:
  • Sheet metal shear-cutting process,

Blanking.

  • Drawing process consist of:
  • Wire drawing process,
  • Tube drawing process,
  • Metal spinning process,
  • Sheet metal drawing process,
  • Ironing process

Friction and lubrication in metal forming process | Friction in metal forming process

  • friction in metal forming take place due to close contact of work piece surface and the tool (die, punch) at high pressure (Also high temperature for some operation).
  • This high pressure, high compressive stress and also friction plays a very important role in forming of the product.
  • But over 50% of energy is required to overcome tis friction.
  • Surface quality is retarded, the tool and die life is reduced.
  • To overcome such undesirable effects lubrication is introduced

To overcome the friction lubrication is carried out:

Lubrication in metal forming process | Types of lubricants used in metal forming

Metal forming uses lubrication: water-based, oil-based, synthetic and solid film

  • Water based: they good for cooling purpose but are has less lubricity. They are mostly used for high speed application.
  • Oil-based: It overcome draw backs of water based lubricant but you lack additive solubility.
  • Synthetic: with solubility it also provides good lubricity.
  • Solid film: can be used with or without oil/water, mostly used for high pressure, low speed and low temp application.

Advantages and disadvantages of metal forming process

Advantages:

  • Material wastage is negligible or zero (As no shear/ cutting action involved).
  • Grain can be oriented in required direction
  • By cold working strengthens and hardness is increasing, while by hot working the ductility and malleability increases.

Limitations:

  • Force and energy required is very high
  • Automation is required, therefore it is costly
  • Except forging all other process can produce uniform cross section.
  • Crossover and undercut are difficult to produce.

Applications of metal forming process

  • Channels of direct shape. 
  • Seamless tubes
  • Turbine-rings.
  • Hardware products like nail, hails
  • Agricultural tools used for sawing and cutting.
  • Military products
  • Automobile structure parts doors, outer body shield. 
  • Different plastic products

Rolling 

Rolling is a process when the required shape is obtained by passing the material through rollers. This rollers are places with distance between them, which is define by the required thickness of the output product. As material is forced to pass through this gap the high force is also applied by the rollers. The number of rollers depends on application of force.

FORMING PROCESS
rolling process

Rolling is carried out by the following methods:

1.) Hot rolling

2.) Cold rolling

3.) By application of front and back tension

Roll forming (hot)

  • Hot rolling is a rolling process (also known as hot working) when the material is heated above its recrystallization temperature before passing it through the rollers.
  • Malleability and ductility increase while strength and hardness decreases
  • Surface finish and dimension accuracy is poor
  • Force and energy required is less as compared to cold rolling
  • Friction is high

Roll forming (cold)

  • Cold rolling is a rolling process (also known as cold working) when the material is heated below its recrystallization temperature before passing it through the rollers.
  • Malleability and ductility decreases while strength and hardness increases
  • Surface finish and dimension accuracy is excellent
  • Force and energy required is more as compared to hot rolling
  • Friction is low

Types of roll forming machine

  • Two-high rolling-mills
  • Three-high rolling-mills
  • Four-high rolling-mills
  • Cluster rolling-mill
  • Planetary rolling-mill
  • Tandem rolling-mill

Sheet metal forming processes and applications | Sheet metal forming processes and die design | Sheet metal roll forming process | Sheet metal forming processes and applications

In forming sheet metal operation the material is deform plastically and no cutting action is carried out.

The force applied in sheet metal forming operation is more than the yield stress so as to carry the deformation but less than the ultimate stress as not cutting action in carried out in forming process.

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Different types of sheet metal forming processes | Types of sheet metal forming process | Types of sheet metal forming processes

  • Bending
  • Deep cup drawing
  • Shearing
  • Stretching
  • Spinning

Bending

Bending is a sheet metal forming operation is where metal is bent in the required direction by applying force with the help of punch and die components. When bending occurs, the outside layers of the sheet go through tension while the inside layer goes through compression. If the stretching is excessive, there might be a chance of shifting the neutral plane towards the center of curvature.

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bending

Stretch forming | Types of stretch forming

It is sheet metal forming process in which the selected sheet is stretch and bended continuously over a die to get the required shape. It acquires the shape of the die.

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stretch forming

Types of the stretch forming:

  • Longitudinal stretch forming
  • Transvers stretch forming

Deep drawing metal forming process

Manufacturing of cup from a raw sheet blank with the help of the punch and die is called deep drawing or cup drawing process, Here the material is deformed plastically to get the required shape. It is a sheet metal forming operation hence no cutting action. Punch is used to apply the force to create plastic deformation of the material. And it gets the shape of the die and punches while going through series of bending, stretching, straighten up to produce a vertical deformation wall of a deep-drawn component.

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deep dawing

Guerin process metal forming

guerin process metal forming is a subpart sheet metal forming process. In this process the sheet metal is stamped with help punch to get desirable result. It is simple shaping of sheet metal by stamping process.

Metal press forming process

Metal press forming is very simple process in which sheet metal is hold with help of the clamps and shaped with help die and punch. It is same as the stamping process.

Spinning process in metal forming | Spinning process in sheet metal forming

In this process the disc of the metal sheet is used as raw product. It is clamp over the spinning machine against the mandrel. The disc of sheet is pressed against the high speed rotating mandrel with help of the press tool. The symmetric objects are manufactured in this process. It can be carried out on the CNC machine.

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Roll forming process in sheet metal

Roll forming in sheet metal is a process when the required shape/size is obtained by passing the sheet metal through rollers. This rollers are placed with distance between them, which is define by the required thickness of the output product. As material is forced to pass through this gap the high force is also applied by the rollers. The number of rollers depends on application of force

Types of roll forming

  • Two-high rolling-mills
  • Three-high rolling-mills
  • Four-high rolling-mills
  • Cluster rolling-mill
  • Planetary rolling-mill
  • Tandem rolling-mill

Defects in sheet metal forming process

Defects in sheet metal:

Wrinkle: the folding create at inside of the deep drawn component is called wrinkle. It can be eliminated by applying blank holding force along strip plate.

Earing defects: The folding created at the flange end of the deep drawn component is called as the earing defect. It is generated because of circumferential compressive stress or anisotropic properties of material. 

It can be eliminated by cutting the material after deep drawing operation by trimming process. The amount of material trimming comes under the trimming allowance.

Scratches: In a deep drawing process because of the friction present between component and the die scratches are generated and it reduces surface quality. It can be eliminated by proper lubrication.

Corner crack or fracture: corner crack or fracture are generated at the bottom of the deep drawn components because of thinning of material and stress concentration. 

Orange peel: When annealing of the deep drawn component is done above recrystallization temperature it is observe that the grain get expanded independently and produce coarse size of grain. Which has some structure like peel of orange. Therefore it is called as orange peel.

Advantages and disadvantages of sheet metal forming process | Advantages of sheet metal forming process

Advantage:

  • Production rate is high
  • Minimum waste
  • Uniform density
  • Simple process
  • High strength
  • Good surface finish

Disadvantage:

  • High force required
  • Heavy machineries
  • Automation required
  • Somewhat poor in maintain accuracy

Forging

Forging is a process in which material if deforms plastically to get the required shape by applying high compressive force with the help of hammers. The compressive force is applied at a particular location several times to get the final product.

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forging

Mostly forging uses a hot working process.

Extrusion | Extrusion metal forming process | Extrusion process in metal forming

Extrusion is a process where a billet is placed inside the stationary cylinder with one end attach to opening with die (Output shape) and another end has a ram to apply the force. 

When the force is applied to a solid billet, it acts in a hydrostatic compressive manner.

At one point, this value will reach the flow stress value of the material, where the entire solid material will become extremely soft, like a gel, and will flow through the die, with the shape of the die.

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Extrusion

Extrusion types:

1) Forward/direct extrusion: Hydrostatic extrusion.

2) Backward/ indirect extrusion: Impact extrusion or hollow back extrusion.

Wire drawing | Drawing metal forming process

Wire drawing is a process where the billet is given the shape of required output by pulling it through a die rather than Appling force from backward as the extrusion.

A typical wired drawing can de dived in four zone.

wire drawing
wire drawing

Zone 1: Deformation Zone

The entry diameter of the zone is equal to the rod diameter of the zone, while the end diameter is the diameter of the wire needed to be. Therefore whatever deformation is required to convert the rod into wire takes place in this zone. It is known as the deformation zone. The total included angle of the stented surface of the deformation zone is called as die angle or deformation angle.

Zone 2: Lubrication Zone

This zone is used to supply lubricant to reduce friction and let the process carry out smoothly. If the lubrication is not provided, it dull, rough, and unpleasant surface finish of the wire.

Zone 3: sizing zone

This zone is just used to maintain the same load for some time to convert elastic deformation into permanent plastic deformation.

Zone 4: Exit or Safety zone

This zone is used for collecting high-pressure and high-temperature lubricants.

Punching metal forming process

Punching is process in which punch is used to apply the force on the work piece to get required output and the result may be in form of the cutting/ shear action depending upon a material. It is mostly used to create holes in a metal sheet.

Advanced metal forming processes | Advanced metal forming process

  • Super plastic forming
  • Electroforming
  • Fine and banking operation
  • Hydro forming
  • Laser forming
  • Powder metal forming process

Powder metal forming process

Power metal forming is process in which raw material is in powder form and is well mix for desired output product composition. The powder is push into the die and the punch is used to apply the force and hold it for a time. To increase the density of the product the heat application is also introduced. It is used to manufacturing of self-lubricating bearing.

Blanking metal forming process

Blanking is the specialized precision metal forming process that includes extrusion in cold manner and advanced stamping techniques. It gives clean and good dimension accuracy products, but cost is very high.

Mostly used to manufacture automobile and electronic parts

Types of plastic for vacuum forming

  • Acrylonitrile Butadiene Styrene
  • Acrylic – Perspex
  • Co-Polyester
  • Polystyrene
  • Polycarbonate
  • Polypropylene
  • Polyethelene

FAQ’S

What are the different metal forming processes | Types of metal forming process | what are the different types of forming | Metal forming process example

1) Bulk metal forming: 

  • Forging
  • Rolling
  • Extrusion 
  • Wire forming

2) Sheet metal forming

  • Bending
  • Deep cup drawing
  • Shearing
  • Stretching
  • Spinning

3) Advanced metal forming

  • Super plastic forming
  • Electroforming
  • Fine and banking operation
  • Hydro forming
  • Laser forming
  • Powder metal forming process

Sheet metal forming process

  • Bending
  • Deep cup drawing
  • Shearing
  • Stretching
  • Spinning

Hot metal forming processes

  • When work is done on the material at a temperature greater than the Recrystallization temperature, such work comes under the category of hot working.
  • The amount of force and energy required in hot working is less.
  • The accuracy maintains poor in hot working as compared to others.
  • Properties like Strength and Hardness decrease while the properties like malleability and ductility increase.
  • Friction acting in hot working is high.

Metal forming process in automobile industry

Mostly sheet metal forming is used in automobile industry.

What are the defects in metal forming process

Rolling Defects:

Spreading: In a rolling when material spread along the width such defect is called spreading. Generally when thickness of the strip is very high and width is less material spread along the width direction

Alligatoring: Because of the excessive shear along a shear plane of a raw material strip sometimes it gets fracture from the center and creates a similar structure as the mouth of the alligator. Therefore it is called as the alligatoring defect.

Waviness: Because of the anisotropic property of the engineering material a waviness I generated on the rolled components, such defect is called as waviness defect.

Extrusion defects:

Bamboo defects: soft crack along the surface of the component.

Fish Tail: It occurs when hot extrusion is carried out with impurities in the billet. It is also called as pipping defect. It create sink hole at the end of billet.

Center Burst: Center burst are the internal cracks present in the product. 

Sheet metal forming defects:

Wrinkle: the folding create at inside of the deep drawn component is called wrinkle. It can be eliminated by applying blank holding force along strip plate.

Earing defects: The folding created at the flange end of the deep drawn component is called as the earing defect. It is generated because of circumferential compressive stress or anisotropic properties of material. It can be eliminated by cutting the material after deep drawing operation by trimming process. The amount of material trimming comes under the trimming allowance.

Scratches: In a deep drawing process because of the friction present between component and the die scratches are generated and it reduces surface quality. It can be eliminated by proper lubrication.

Corner crack or fracture: corner crack or fracture are generated at the bottom of the deep drawn components because of thinning of material and stress concentration. 

Orange peel: When annealing of the deep drawn component is done above recrystallization temperature it is observe that the grain get expanded independently and produce coarse size of grain. Which has some structure like peel of orange. Therefore it is called as orange peel.

Is the panel beating metal forming process still in use nowadays

Yes, panel beating is still used now a days. Mostly in small automobile shops to recovery the damage part.

What factors influence formability in metal forming

Properties like, ductility, malleability and formability are important in metal forming.

Is there any difference between sheet metal working process and sheet metal forming process

Yes, in sheet metal work we involve cutting/ shearing apart from forming action but in sheet metal forming the sheet does not go under cutting action. Sheet metal forming is a subpart of metal working.

What is the difference between forming and shaping processes

Forming is the process where the billet is converted and form in a particular shape with the application of compressive force. The volume changes is negligible.

Shaping is the process where the material is cut and machined to get the required output product. The sharp cutting tools are used to machine the material. The volume change take place.

What are some common uses for sheet metal

In automobile, Aircrafts covering.

In domestic appliances: iron covering, washing machine body, fan blades, cooking utensils etc.

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Read more about Quasi-Static Process.