Spectrum Controls 1771sc-IFE32 - Manual (Page 42)

32 PLC-5 TM 32-Channel Analog Input Module
1. Make sure the field wiring arm is in position on the module.
2. Apply power to the 1771 I/O chassis.
3. Check each input (either single-ended or differential) for common mode voltages
exceeding +14.25V with respect to module common.
A. Hold the positive probe of the voltmeter on the first input terminal.
B. Hold the negative probe of the voltmeter on a module common terminal
(terminals 20 or 21).
4. If any voltage is seen that exceeds +14.25V, remove that channel’s input wiring and
observe the affect on the input data table of the programmable controller.
ATTENTION: Remove power from the 1771 I/O chassis backplane and field wiring
arm before removing or installing input wiring.
• Failure to remove power from the backplane or wiring arm could cause module
damage, degradation of performance, or injury.
• Failure to remove power from the backplane could cause injury or equipment
damage due to possible unexpected operation.
If no other common mode voltages are present, the input data for all other channels
should stabilize to some predictable value.
5. Attempt to equalize all grounds at the offending channel beforereconnecting the
input wiring.
ATTENTION: Remove power from the 1771 I/O chassis backplane and field wiring
arm before removing or installing input wiring.
• Failure to remove power from the backplane or wiring arm could cause module
damage, degradation of performance, or injury.
• Failure to remove power from the backplane could cause injury or equipment
damage due to possible unexpected operation.
6. If the common mode voltage cannot be removed on the input, an isolation device
may be required on that channel.
Disconnecting inputs from the field wiring arm one at a time while observing module
action.
During this procedure, monitor the input data table of the programmable controller
and observe any changes which occur.
1. Make sure the field wiring arm is in position on the module.
2. Apply power to the 1771 I/O chassis.
3. While observing the input data table, remove one input at a time.
ATTENTION: Remove power from the 1771 I/O chassis backplane and field wiring
arm before removing or installing input wiring.
• Failure to remove power from the backplane or wiring arm could cause module
damage, degradation of performance, or injury.
• Failure to remove power from the backplane could cause injury or equipment
damage due to possible unexpected operation.
4. When the offending input channel is disconnected, the input data table will
stabilize to some predictable values.
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