Wired Temperature Sensor: A Comprehensive Guide

Wired temperature sensors are essential devices used to measure the temperature of an environment or object and transmit this information to a data acquisition system or controller. The selection of a temperature sensor depends on various factors, including temperature range, package size, thermal response time, electrical response time, heat sinking, thermal mass, robustness, compatibility with harsh environments, easily measured signal, compatibility with sources of error, high sensitivity, high accuracy, high repeatability, low power dissipation, interchangeability, ease of use, low cost, available accessories, and available instrumentation.

Temperature Sensor Types and Specifications

Germanium Resistance Temperature Sensors

Germanium resistance temperature sensors are recognized as “Secondary Standard Thermometers” and have been employed in the measurement of temperature from 0.05 K to 30 K for more than 40 years. They have a useful temperature range of about two orders of magnitude, and their resistance varies from several ohms at their upper useful temperature to several tens of kilohms at their lower temperature. These sensors are very useful for submillikelvin control at 4.2 K and below due to their high sensitivity and excellent reproducibility.

Repeatability

Repeatability is the closeness of agreement among a number of consecutive measurements of the output for the same value of the input under the same operating conditions, approaching from the same direction, for full-range traverses. It is usually measured as a non-repeatability and expressed as repeatability in percent of span. It does not include hysteresis.

Resolution

Resolution is the minimum possible change in input required to produce a detectable change in the output when no reversal of the input takes place. Resolution is typically expressed as a percent of the input span.

Response Time

Response time is usually measured by a parameter that includes both dead time and time constant. When applied to the valve, it includes the entire valve assembly. A second-order system or device is one that has a dynamic relationship between the input and output, characterized by a second-order equation.

Technical Specifications of Wired Temperature Sensors

Specification	Description
Temperature Range	The range of temperatures that the sensor can accurately measure. This can vary from cryogenic temperatures (e.g., 0.05 K to 30 K for germanium resistance sensors) to high temperatures (e.g., up to 1800°C for some thermocouples).
Package Size	The physical dimensions of the sensor, which can range from micro-sized sensors for embedded applications to larger sensors for industrial use.
Thermal Response Time	The time it takes for the sensor to respond to a change in temperature. This is affected by factors such as the sensor’s thermal mass and the heat transfer characteristics of the environment.
Electrical Response Time	The time it takes for the sensor’s electrical output to respond to a change in temperature. This is affected by factors such as the sensor’s electrical characteristics and the data acquisition system.
Heat Sinking	The ability of the sensor to dissipate heat, which can affect its accuracy and stability.
Thermal Mass	The amount of heat required to change the sensor’s temperature, which can affect its response time.
Robustness	The sensor’s ability to withstand environmental factors such as vibration, shock, and corrosive atmospheres.
Compatibility with Harsh Environments	The sensor’s ability to function accurately in challenging environments, such as high temperatures, high pressures, or the presence of electromagnetic interference.
Easily Measured Signal	The sensor’s ability to provide a clear, easily interpreted electrical signal that can be readily measured by data acquisition systems.
Compatibility with Sources of Error	The sensor’s ability to minimize or compensate for sources of error, such as self-heating, lead resistance, or thermal gradients.
High Sensitivity	The sensor’s ability to provide a large output signal for a given change in temperature, which can improve measurement accuracy.
High Accuracy	The sensor’s ability to provide measurements that closely match the true temperature value.
High Repeatability	The sensor’s ability to provide consistent measurements under the same conditions.
Low Power Dissipation	The sensor’s ability to operate with minimal power consumption, which can be important for battery-powered or remote applications.
Interchangeability	The sensor’s ability to be easily replaced with another sensor of the same type without the need for recalibration or significant changes to the measurement system.
Ease of Use	The sensor’s ability to be easily installed, configured, and integrated into a measurement system.
Low Cost	The sensor’s affordability, which can be an important factor in many applications.
Available Accessories	The availability of accessories, such as mounting hardware, cables, and signal conditioning modules, that can simplify the integration of the sensor into a measurement system.
Available Instrumentation	The availability of compatible data acquisition systems, controllers, and other instrumentation that can be used to interface with the sensor and process the temperature data.

Conclusion

Wired temperature sensors are versatile and essential devices used in a wide range of applications, from cryogenic temperature measurement to high-temperature industrial processes. By understanding the various types of temperature sensors and their technical specifications, users can select the most appropriate sensor for their specific needs, ensuring accurate and reliable temperature measurements.

References:
– Sensor Technology Handbook
– OLLINTEC Temperature Measurement and Control Catalog
– Lake Shore Cryotronics
– Digital Habit Evidence – Duke Law Scholarship Repository
– SmartMesh WirelessHART Application Notes – Analog Devices
– CONTROL VALVE HANDBOOK | Emerson