An accurate determination of temperature is one of the essential factors across process industries. Obtaining precise temperature plays a vital role in deciding the quality and consistency of the final product. Also, temperature measurement and control is part of many processes to not only get the desired output, but also keep the system working as expected. This is because the temperature should be maintained in the required range and not exceed beyond the given upper limit. Different types of temperature measurement devices are used to control the temperature level within the given range. Resistance thermometer detectors or RTDs and thermocouples are being used from decades for temperature sensing and control in various manufacturing processes. RTDs and thermocouples have evolved with time and hence can automate the temperature control process as well as facilitate remote access and control to the operator. Both RTDs and thermocouples can measure temperature in a broad range of applications. Now you may ask which is better RTD or thermocouple? This post discusses differentiating factors between RTDs and thermocouple sensors in terms of their applications. So, stay tuned.

Resistance Thermometer Detectors vs Thermocouples – Know Differential Characteristics

Here are some important factor considerations when differentiating resistance thermometer detectors and thermocouples. So, let’s have a look at them.

  • Introduction: Thermocouples sense and measure temperatures using two dissimilar wires. Owing to their different compositions, wires offer different electric conductivity. They find applications for temperature measurement and control in segments such as diesel engines, gas turbine exhausts, and more. On the other hand, RTDs are devices that measure temperature based on the change in resistance of a metal. The resistor rises more or less based on the temperature change. Hence, the measurement of the temperature is relative and not absolute. RTDs are widely used across industries where even a slight change in the temperature impacts the process.

  • Construction: This is another important factor for consideration. RTDs are made using a metal wire and materials that do not contain iron. The wire is wounded on the glass to create RTDs. The metal wires are constructed using nickel, copper, and platinum alloy as they have a positive temperature coefficient. Probe RTDs and surface mount RTDs are types that are widely used across industries. As discussed earlier, thermocouples are constructed using a pair of dissimilar conductor materials such as tungsten and platinum alloys.

  • Working: RTDs operate based on the composition between temperature and metal resistance. The temperature is directly proportional to the RTD resistance. This means the resistance of RTDs rises with the rise in temperature and vice versa. RTDs sense this shift in the temperature and can correlate it with a specific temperature. On the other hand, thermocouples function based on the Seeback effect, which is seen when two dissimilar metals create a closed circuit at two separate junctions. An electromotive force or EMF is induced in the circuit when the change in the temperature is observed.

  • Temperature Measurement Level: RTDs work well with temperatures up to 400°C. Advanced RTDs are designed especially for higher temperatures. Thermocouples work well in temperatures up to 2500°C.

  • Sensitivity: Both RTDs and thermocouples give quick responses to temperature changes. However, thermocouples are three-time faster than RTDs.

  • Accuracy: RTDs can be designed with tight tolerances and offer more accurate output than thermocouples. They can detect differences as close as +or- 0.1°C, while the output offered by thermocouples may fluctuate by + or – 1-2°C.

  • Cost: Thermocouples are more economical than RTDs owing to their simple and low-cost manufacturing process. Typically, they are used where some amount of temperature change is tolerated by the process.

Now that the comparison between RTDs and thermocouple sensors is known, you can select the best-suited one for your application, depending on the accuracy you require. When selecting temperature sensors for your applications, don’t compromise on quality as it makes a significant difference. Ensure to source the temperature sensors from a trusted manufacturer and supplier like The Transmitter Shop. With years of industry experience and highly skilled employees, the company offers high-quality, performance-driven temperature sensors of different types and features.