8
3.3 Calibration Procedures
Connect the calibration equipment according to
Figure 3-1
or
3-2
. The
thermocouple wire must be of the same calibration as the transmitter being
calibrated. Make sure that the wiring polarities are correct. (Note that the
RED thermocouple wire is NEGATIVE).
To check or adjust the calibration:
1.
Locate the Z (zero) and S (span) potentiometers.
2.
Select, from Table 3-1, the correct mV input values for the Z (zero)
and S (span) adjustments that correspond to the model number.
For example, for Model TX93A-J2, the Z input is -0.886 mV, and the S
input is 4.907 mV.
If a Thermocouple Calibrator/Simulator is used, such as the Model
CL511 Precision Calibrator, select the Temperature Input Z (zero) and
S (span) values.
3.
Set the dc mV source to the selected Z (zero) mV value. Adjust the
Z potentiometer to read 4.000 mA on the monitoring instrument.
4.
Set the dc mV source to the selected S (span) mV value. Adjust the
S potentiometer to read 20.000 mA on the monitoring instrument.
5.
Repeat steps 3 and 4, as required, until the readings are exactly
4.000 mA and 20.000 mA. This procedure is necessary since there is
interaction between the two potentiometers.
