Watlow Calibrating Watlow Series 988 Family Process Controls - Manual (Page 8)

Low Gain Thermocouple Input Procedure
For all thermocouple inputs excluding Type R, S and B
Equipment Required
•
Type J reference compensator with reference junction at 32
°
F/0
°
C, or
Type J 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 voltage L1, L2 and ground to the proper terminals on the Series
988. See Chapter 2 in the user's manual.
2. For Input #1 calibration: Connect the millivolt source to terminal #9 (+) and
terminal #10 (-) on the 988 terminal strip. Use 20 to 24 gauge copper wire. If
you have model number 98_ _ - 2 _ _ _ - _ _ _ _, remove the control from the
case and set the Input 1 DIP switches to:
1 OFF 2 ON 3 ON
For Input #2 calibration: Connect the millivolt source to terminal #19 (+) and
terminal #20 (-) on the 988 terminal strip. Use 20 to 24 gauge copper wire. If
you have model number 98_ _ - _2 _ _ - _ _ _ _, remove the control from the
case and set the Input 2 DIP switches to:
1 OFF 2 ON 3 ON
3. Apply power to the unit and let it warm up for 15 minutes. After warm-up, put
the unit in the CAL menu. See Page 6.
When performing calibration procedures, always do the Input 1 prompts
(beginning with an “A”) first, then continue on to the Input 2 prompts
(beginning with a “B”). See the Calibration menu on Page 6.
4. At the A 50 prompt, or the B 50 prompt, enter 50.00mV from the millivolt source
to the Series 988. Allow at least 10 seconds to stabilize. Press the Up key to
change the upper display to YES. Press the Mode key.
5. At the A 00 prompt, or the B 00 prompt, enter 0.00mV from the millivolt source
to the Series 988. Allow at least 10 seconds to stabilize. Press the Up key to
change the upper display to YES. Press the Mode key.
6. At the tc prompt, disconnect the millivolt source, and connect the reference
compensator or T/C calibrator to terminal #9 (+) and terminal #10 (-) on the 988
terminal strip. If using a compensator, turn it on and short the input wires.
When using a Type J calibrator, set it to simulate 32
°
F/0
°
C. Allow 10 seconds
for the control to stabilize. Press the Up key to change the upper display to
YES. To conclude the T/C calibration, press the Display key.
8
WATLOW Series 988 Calibration Manual
Low Gain T/C
NOTE:
Any prompt begin-
ning with an “A”
applies to Input 1.
Those beginning
with a “B” apply to
Input 2.