Calibration Procedures 3
34980A Service Guide 77
Thermocouple Reference Junction 34921A (Optional)
To make a thermocouple measurement a known reference junction temperature
measurement must be made. The reference junction temperature is measured by two
solid state temperature sensors in the input connection area on the module. The
adjustments store calibration constants used to correct the measurements from the
temperature sensors.
Thermocouple measurements using an internal reference are only supported by the
34921A module using the optional 34921T terminal block. The isothermal block is
located on, and is an integral part of,
the terminal block.
There are no adjustments for the reference junction.
Thermocouple Reference Junction Verification
1 Read “Plug-in Module Test Considerations" on page 67.
2 Connect a calibrated thermocouple to channel 21.
3 Install the module in slot 1.
4 Place the J Type calibrated thermocouple at a known temperature
(ice bath or calibrator).
5 Select Channel 21. Configure the channel as follows:
TEMPERATURE
THERMOCOUPLE
J TYPE
INTEG 10 PLC
INTERNAL REF
SENS:TEMP:TRAN:TYPE TC,(@1021)
SENS:TEMP:TRAN:TC:TYPE J,(@1021)
SENS:TEMP:NPLC 10,(@1021)
SENS:TEMP:TRANS:TC:RJUN:TYPE INT,(@1021)
6
Subtract the thermocouple error from the measured temperature.
Verify the result is within ± 1.0 °C of the known temperature (set in step 4).
You should perform these verification if you are using the module for
thermocouple measurements.
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