Temperature reigns as the most often measured process parameter in industry. While temperature measurement utilizes sensors of many forms, the actual measurement of temperature is accomplished via only five basic sensor types: Thermocouple (T/C), Resistance Temperature Detector (RTD), Thermistor, Infrared Detector, and via semiconductor or integrated circuit (IC) temperature sensors. Of these five common types, the thermistor is perhaps the most commonly applied for general purpose applications. Semiconductor sensors dominate most printed circuit board or board level sensing applications. Infrared is used for non-contact line-of-sight measurement. But for industrial applications that typically employ remote sensing, thermocouples and RTD’s reign as the most popular sensor types.
Most industrial applications require that a temperature be measured remotely, and that this signal be transmitted some distance. An industrial transmitter is commonly used to amplify, isolate, and convert the low-level sensor signal to a high level signal suitable for monitoring or retransmission. With respect to these transmitters, your choice of sensor type is generally limited to T/C, or RTD. But given the wide variety of RTD and T/C types, how do you choose the best sensor type for your specific application? This paper will look at important characteristics of these two main industrial sensor types and offer information to help you select the best type for your
application. Part 1 explores the thermocouple. Part 2 looks at the RTD. Part 3 compares thermocouples and RTD’s and gives information for choosing between them.