Here’s how to do a simple comparison calibration of a probe-style RTD at one temperature point using temperature sensor calibration equipment, a dry-block calibrator in this case.  Fully insert the probe RTD into one of the dry-block insert holes and connect the cable to an RTD temperature readout.  Ramp the dry block to 100 ºC (212 ºF).  When the dry-block display shows a stable 100 ºC, record the value of the RTD temperature readout.  You now have one data point to compare the RTD temperature on the readout to the dry-block calibrator which is being used as a stable measurement reference standard.  A typical sensor calibration would be done at several temperature points that span the working range of the sensor when used in a production environment

Comparison calibration using a dry-block calibrator


For a higher accuracy calibration, a reference PRT connected to a thermometer readout could be inserted into another of the dry-block insert holes.  In this case, the PRT which has a higher accuracy than the internal display of the dry-block calibrator is used as the reference standard and compared to the reading of the RTD temperature readout. 


Comparison calibration using a reference PRT with dry-block


Please read Selecting a dry-block calibrator for help in choosing the right dry-block calibrator.