WATLOW Series 942 User's Manual
57
Appendix
RTD Calibration
RTD Field Calibration Procedure
Before attempting any calibration procedure, make sure you have the
proper equipment called for in each procedure.
Equipment Required
•
1K
Ω
precision decade resistance box with 0.01 ohms resolution.
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 decade resistance box to Terminal #4, 5 and 6 on the ter-
minal strip. Use regular 20 - 24 gauge wire of the same length and type.
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 the
rLO
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
calibration equipment. When you have completed all of the RTD 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
rLO
parameter, set the decade resistance box to the correct low
setting. See the table below. This parameter can be calibrated to JIS or
DIN. Allow at least 10 seconds to stabilize. Press the MODE key.
6.
At the
rHI
parameter, set the decade resistance box to the correct high
setting. Allow at least 10 seconds 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 RTD calibration,
advance the MODE key to the next parameter or exit the Calibration menu
by pressing the HOLD/RUN key twice.
NOTE:
Not all parameters
will appear. They
are dependent on
your unit type. Use
only the steps that
apply to your unit.
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.
Calibration
Low
High
1
°
17.31
317.33
0.1
°
59.59
177.13
942A-3XX0-0000
Table 7 -
RTD Settings.
942A-2XX0-0000
