Watlow Series 985 - Manual (Page 42)

0-20/4-20mA Output Field Calibration Procedure
NOTE
Not
all parameters
will appear. They
are dependent on
your unit type. Use
only the steps that
apply to your unit.
Equipment Required
l
470 ohm 1/2 watt 10% resistor.
l
4 - 1/2 digit Digital Multimeter.
Setup And Calibration
NOTE
1.
2.
3.
Before calibration on an installed control, make sure all data and
parameters are documented. See Setup and Operation Charts,
Pages 26 and 28.
Connect the AC line voltage Ll , L2, and ground to the proper terminals of
the 980/985. See Chapter 2.
Connect the multimeter in series with the 470 ohm resistor to Terminal #1 (+)
and #3 (-) for 0-20mA units, on the Series 980/985 terminal strip. Use
Terminal #I (+) and #2 (-) for 4-20mA units. Use regular 20 - 24 gauge
wire.
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 Figure 33 on Page 37.
Press the MODE key until the 4A0 prompt is displayed.
IMPORTANT:
When the MANUAL LED 's ON the unit is automatically calibrating. Your
sequence is VERY important. Always move to the next prompt before
changing the calibration equipment.
4.
5.
6.
7.
8.
9.
Press the AUTO/MAN key twice to enter the MANUAL mode. The unit is
calibrating when the MANUAL LED is ON.
At the 4A0 prompt, the multimeter should read approximately 0mA for 0-
20mA units and 4mA for 4-20mA units. Allow at least 10 seconds to
stabilize.
Use the UP/DOWN keys (reverse acting) to adjust the reading on the
multimeter for 0.0mA ±0.1 OmA on 0-20mA units and 4.0mA+/-0.2mA on
4-20mA units. Press the MODE key.
At the 2AO prompt, the multimeter should read approximately 20mA.
Allow at least 10 seconds to stabilize.
Use the UP/DOWN keys (reverse acting) to adjust the reading on the
multimeter for 20.0mA ±0.10mA on 0-20mA units and 20.0mA+/-0.2mA
on 4-20mA units.
Press the AUTO/MAN key twice to exit the MANUAL mode. This pauses
calibration to exit the CAL mode.
42
WATLOW Series 980/985 User’s Manual