5 Steps to Calibrate an RTD

If you are calibrating a medium to high accuracy
RTD, you will probably use the characterization
method of calibration. Characterization is the
type of calibration in which the device under
test (DUT) resistance is determined at several
temperature points and the data are fitted to a
mathematical expression.
To calibrate an
RTD, perform these steps:
1. Place the reference probe and the DUTs in the
temperature source. Make sure they are all placed
as close together as possible, in a radial
pattern with the reference probe in the center of
the circle.
2. Connect the leads to the readout(s), using the
proper 2-, 3-, or 4-wire connection.
3. Measure the reference probe and determine the
temperature. Ideally, you would use a readout
designed for temperature work that can measure
the resistance and calculate the temperature from
calibration coefficients previously entered into
the readout.
4. Measure and record the resistance of the
DUT(s). Since the DUTs are resistance
thermometers similar to the reference probe, they
are measured in a similar manner. It is also good
practice to close the process by measuring the
reference probe one more time.
5. Fit the data. Data fitting is a process in
which you solve a set of simultaneous equations
which contain the calibration data to arrive at a
set of coefficients unique to the RTD and
calibration. There are several software programs
available to accomplish this task.
Recommended
Products
5618B Small Diameter Industrial RTD
1586A Super-DAQ Precision Temperature Scanner
9170, 9171, 9172, & 9173 Metrology Well
Calibrators
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