Do i ever need to calibrate PT100 probes?

[mbartoli]

I concur with the majority sentiment here... the RTD itself cannot be calibrated, only compared to a certified standard. We use Rosemount RTD transmitters (4-20mA)here by the hundreds; our Metrology lab will annually calibrate the transmitters with a certified standard. Our installation standard for RTD instruments specifies termination at the instrument and PLC only, with no intermediate termination points. This minimizes the possibilities of a poor connection affecting the reading.

 

[AustralIan]

Hmm, I think the term 'calibrate' cause confusion because it has more than one meaning.

Calibrate means to check or adjust to a standard. Many see it as strictly check AND adjust.

So if I was tasked to calibrate an RTD, I would remove the RTD, put it in somethings I knew the temperatures of and record its resistance after some settling time, and write the deviation from the standard. What you then do with that is another question.

If you increase the temperature beyond the maximum limits of the PT100, it can melt and deform, giving an off reading.

 

[AustralIan]

If you use an IO-Link RTD, you can access it's calibration from a central database, and have your PLC automatically adjust based on which serial number RTD you grabbed off the shelf and plugged in.

 

[dcam]

The whole RTD topic is what we give to new E/I techs to learn and master first. There are several instrumentation and metrology principles that are reinforced with this task.

The very small platinum element and hair like wires (3 in this case-1 "odd man out" and 2 electrically "the same") are encased in a temperature engineered epoxy inside a Stainless Steel housing never to move or see the light of day again. It cannot have its temperature/resistance characteristics changed.

These instruments next connect to a Wheatstone bridge then an rtd input module or a R/I. What ever adjustments are made after the physical RTD, cannot effect the RTD itself. This thread has evolved into a wording issue.

I invite all newer knowledge seekers to start taking broken instruments apart. This will help tremendously in understanding.