#WishIknew Thermocouple or RTD?


When you have a question about process automation that needs a short answer, let us know with #WishIknew and #Visaya! We’ll reply with a #WishIknew post. It’ll give a quick explanation, then some related articles, videos, or reviews if you want to know more.

I wish I knew whether to use a thermocouple or RTD!

This answer depends on the max temperature in your process and other factors. For instance, a resistance temperature detector (RTD) can measure up to 1000 degrees Celsius, but a thermocouple (TC) can go up to  1700 degrees Celsius.

However, if your temperature goes higher than 400 degrees Celsius, the accuracy of an RTD will drop. This limitation has created a rule broadly accepted in the industrial world: Under 850, you can go with RTDs. Over 850 degrees Celsius, use a TC.

You also have other factors to consider beyond temperature. TCs have better response times than RTDs, but RTDs have better long-term stability and overall accuracy. So if you have a high-heat application that doesn’t need pinpoint accuracy but does need to run for 20 years, maybe you’ll want to think about an RTD!

This video has more temperature stuff: