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RTD Reading Fluctuation
Cause of RTD reading fluctuation?

hello everyone. I am instrument technician and I have one question regarding the RTD output.

The range is --50~60c and its a located on suction line of the compressor. The problem is the reading fluctuate once and become normal. I checked the wires and resistance all found ok.

What will be the possible cause for the fluctuation of the reading?


possibly vibration related to a combination blade passing frequencies and thermowell vibration, etc.

do you have dimensional specifics, flows etc?

>do you have dimensional specifics, flows etc?

Thanks for your response. I will try to get the information and let you know.

Another thing, same RTD related. Sometimes it's showing low reading and when we attend didn't find any loose so after loosen and tighten the termination its become ok. why its behaving like that?

By laplace1050 on 22 April, 2017 - 2:16 am

Hello, how mutch is this fluctation ? first possiblity cause for me is vibration, but can also be RTD becoming bad is fluctation go to very high value.

Did you check the wiring termination? possibly from loose connection in the terminal.

Or you can check the ground cable. My suggestion is take out the RTD and measure using multimeter (ohm). If everything is normal then it must be problem on your wiring/cable.

you checked the external wiring, so it is likely in the sensor itself, RTD's tend to be easily damaged.

Sometimes this problem comes from interference signals.

So you need to check if the RTD cable near to a power cable or not.
Also check the temperature transmitter cable (if there is) also this should be not near any power cable.

it could be from vibration, transmitter electronic problem, cable earthing problem or the reciving channel at PLC/Controller problem.