RTD Temperature Sensor Calibration Procedure

Typically, RTD temperature sensors are checked when calibrating connected equipment, such as panel gauges or temperature transmitters. However, if a problem is suspected with the temperature sensor, the sensor calibration can be performed separately from the calibration of the process electronics.

Calibrate and test RTD sensors

The on-site inspection of the temperature sensor can be easily carried out using a dry block or a temperature bath. For best results, calibrate the temperature sensor completely on the workbench.

Calibration procedure:

Isolate the sensor from the process.
Completely immerse the sensor in an accurate temperature source, such as a dry well or bath that can cover the required temperature range.
For best accuracy, temperature standards can also be completely immersed in a dry well or bath for comparison.
To check the calibration of the RTD temperature sensor separately from the control system temperature indicator, disconnect the RTD temperature sensor from the electronics/transmitter.
Connect the maintenance RTD temperature sensor to a precision instrument that can measure resistance, such as a decimal resistance box or a multi-function calibrator.
Adjust the temperature of the bath or dry well to each test point. Say 25 ℃, 50 ℃, 75 ℃, 100 ℃ and so on.
At each test point, record the temperature bath reading and RTD temperature sensor output reading at each test point.
If the RTD temperature sensor is measured separately from its measuring electronics, compare the measured resistance with the expected resistance in the applicable RTD temperature sensor thermometer. Otherwise, compare the reading on the instrument display with the reading of the temperature standard (possibly a dry well).
Note: The above steps are the same as those for 2-wire 3-wire or 4-wire RTD temperature sensors. Simply connect the corresponding wiring of the RTD temperature sensor in the Decade resistance box or multi-function calibrator used to measure the resistance of the RTD temperature sensor.