How to choose the right temperature sensor technology (RTD or Thermocouples)
Feb 2, 2023
This depends mainly on the temperature range and accuracy. Furthermore, it also depends on other variables, such as costs, ruggedness of the application, vibration resistance, etc. Thermocouples probes have a wider temperature range, RTD probes are more accurate in a certain set temperature range.
Thermocouples usually have a better resistance against vibration. So in applications where vibration is high, thermocouples are recommended. RTD sensors tend to be a bit more costly when looking at the complete sensor. Installation costs for RTD sensors are lower because simple copper wires can be used.
The most accurate way to measure temperature is by using a Resistance Temperature Detector (RTD). However, the temperature range of an RTD sensor is limited compared to a thermocouple. Therefore, at higher temperatures (e.g. >650°C) thermocouples tend to be more accurate.
What is the most accurate way of measuring temperature?
The most accurate way to measure temperature is by using a Resistance Temperature Detector (RTD). However, the temperature range of an RTD sensors is limited compared to a thermocouple. Therefore, at higher temperatures (e.g. >650°C) thermocouples tend to be more accurate.
When do you need an thermocouple sensor?
When you need resistance and stability at high temperatures, then a tc sensor is a good fit. Thermocouple sensors do have a lower accuracy than other technologies, it is good to keep that in mind. Thermocouple sensors do have a short response time and are more affordable then an RTD sensor.
Thermocouple Symbol - Thermocouple Chemical composition - Recommended max. working temperature
Type E | Cu-CuNi | 850°C
Type J | Fe-CuNi | 750°C
Type K | NiCr-Ni | 1200°C
Type N | NiCrSil-NiSil | 1200°C
Type T | Cu-Ni | 350°C
Type S | Pt10%Rh-Pt | 1450°C
Type R | Pt13%Rh-Pt | 1450°C
Type B | Pt30%Rh-Pt6%Rh | 1700°C
Type C | W5%Re-W26%Re | 2200°C
Type D | W3%Re-W25%Re | 2200°C
When do you need an RTD sensor?
RTD sensors are often used when high precision measurement is needed in a certain set temperature range. You can find an overview of the different RTD classes in sequence based on accuracy here; https://kamet-trading.com/faq/pt100-how-accurate-is-an-rtd-sensor/
Usually RTD sensors are used within temperature ranges of -200°C to 850°C. RTD sensors are in favor when it comes to linearity and have high repeatability. Over 90% of RTD sensors are designed for temperatures below 400°C.
Which thermocouple or RTD wire do I need?
Both options have their advantages and limitations. Kamet can and will help you to find the right wire type for your process or application. Before we make an offer we always like to have a call or meeting to discuss the required specifications.