WATLOW Series 942 User's Manual
61
Appendix
NOTE
Before calibration on
an installed control,
make sure all data
and parameters are
documented. See
the Setup and
Operation Tables,
and the Master Step
Chart, Pages 27, 30
and 35.
0-20/4-20mA Output
0-20/4-20mA Output Field Calibration Procedure
Before attempting any calibration procedure, make sure you have the
proper equipment called for in each procedure.
Equipment Required
•
470
Ω
, 1/2 watt 10% resistor.
•
4 1/2 digit Digital Multimeter.
Setup and Calibration
1. Connect the AC line voltage L1, L2, and ground to the proper terminals of
the 942. See Chapter 2.
2. Connect the multimeter in series with the 470
Ω
resistor to Terminal #17 (+)
and #18 (-) for 4-20mA units, on the Series 942 terminal strip. Use Termi-
nal # 17 (+) and #16 (-) for 0-20mA units. 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. Press the MODE
key until
O1LO
parameter is displayed.
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 calibra-
tion equipment. When you have completed all of the 4-20mA output 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
O1LO
parameter, the multimeter should read approximately 0mA for
0-20mA units and 4mA for 4-20mA units. Allow at least 10 seconds to
stabilize.
6. Use the UP/DOWN keys (reverse acting) to adjust the reading on the
multimeter for 0.0mA
±
0.10mA on 0-20mA units, and 3.85mA
±
0.10mA on
4-20mA units. Press the MODE key.
7. At the
O1HI
parameter, the multimeter should read approximately 20mA.
Allow at least 10 seconds to stabilize. The unit will leave the CAL mode if 1
minute passes between key activations.
8. Use the UP/DOWN keys (reverse acting) to adjust the reading on the
multimeter for 20.0mA
±
0.10mA on 0-20mA units and 20.15mA
±
0.10mA
on 4-20mA units.
9. Press the HOLD/RUN key twice to exit the RUN mode. To conclude the
output calibration, advance the MODE key to the next parameter or exit the
Calibration menu by pressing the HOLD/RUN key twice. Press the HOLD/
RUN key twice to exit the RUN mode.
