How to verify the calibration of a average temperature sensor


Thread Starter

Toni Kaesbeck


Does anybody have experience in how to verify the calibration of an average temperature sensors when this sensor has multiple RTD or T/C.
With a single element sensor we may use a calibration bath, but in the case of a very long sensor such as the multiple elements temperature sensor, do we have to use a specially designed calibration bath? Is there an alternative method to the bath?

Thank you!
Toni Kaesbeck

Richard King

Hi Toni,
To check an averaging sensor in a bath, the entire sensor must be placed in the bath (if the bath is long enough, then no problem). We used 13 foot MIMS single element type k T/C to measure exit product temperature at 700 deg C. We calibrate the Transmitter with a mV calibrator
and check the T/C for continuity. If we suspect it, we replace it.

Checking Methods (Not for calibration)
For a T/C nothing beats a calibration bath, but in theory I guess you could heat/cool the cold junction keeping the element at room temperature and measure the mV. You would need to be sure you knew where the cold junction was (I am not sure how this probe is wired).

For RTD, simply read the resistance (this will be a function of how many RTD elements there are) at room temperature. If the resistance corresponds to
the room temperature then it is ok.

If there was a bad connection that is only evident when the probe expands at higher temperatures, then the only method I am aware of, other than a bath, is to check it with a known good probe placed in the process beside the
suspect probe (or hot swap them).

I hope this information helps.

Richard King