56
WATLOW Series 942 User's Manual
Appendix
T/C Calibration
NOTE:
Before calibration
on an installed
control, make sure
all data and para-
meters are docu-
mented. See the
Setup and Operation
Tables, and the
Master Step Chart,
Pages 27, 30 and 35.
NOTE:
Not all parameters
will appear. They
are dependent on
your unit type. Use
only the steps that
apply to your unit.
Thermocouple Field Calibration Procedure
Before attempting to calibrate, make sure you have the proper equipment
called for in each procedure.
Equipment Required
•
Type "J" or "R" reference compensator with reference junction at
32
°
F/0
°
C, or
Type "J" or "R" thermocouple calibrator set at 32
°
F/0
°
C.
•
Precision millivolt source, 0 - 50mV minimum range, 0.01mV resolution
Setup And Calibration
1. Connect the AC line voltage L1, L2, and ground to the proper terminals on
the 942. See Chapter 2.
2. Connect the millivolt source to Terminal #9 Negative and Terminal #7
Positive on the Series 942 terminal strip. Use regular 20 - 24 gauge wire.
3. Apply power to the unit and allow it to warm up for 15 minutes.
After warm-
up
put the unit in the CAL menu. See Page 54.
IMPORTANT:
When the RUN LED is ON the unit is automatically calibrating. Your
sequence is VERY important. Always move to the next parameter before
changing the calibration equipment. When you have completed all of the
thermocouple calibration parameters, press the HOLD/RUN key twice.
Failure to do so will result in inaccurate calibration values.
4. Press the HOLD/RUN key twice to enter the RUN mode. The unit is
calibrating when the RUN LED is ON. Make sure the unit is in the RUN
mode
only
when you are in the correct parameters. See Page 55.
5. At the
tCL
parameter, enter 0.00mV from the millivolt source to the control.
Allow at least 10 seconds to stabilize. Press the MODE key.
6. At the "
CH
parameter, enter 50.00mV for type "J" units or 16.035mV for type
"R" units from the millivolt source to the Series 942. Allow at least 10
seconds to stabilize. Press the MODE key.
7. At the
tC
parameter, disconnect the millivolt source, and connect the
reference compensator or T/C calibrator to Terminal #9 Negative, and
Terminal #7 Positive on the Series 942 terminal strip. Allow 10 seconds for
the control to stabilize. The unit will leave the CAL mode if 1 minute passes
between key activations. Press the HOLD/RUN key twice to exit the RUN
mode. To conclude the thermocouple calibration, advance the MODE key to
the next parameter or exit the Calibration menu by pressing the HOLD/RUN
key twice.
