Rockwell Automation Publication 1794-UM061B-EN-P - March 2020 107
Interpret the Indicators Appendix A
For 3-wire sensors:
• an open fault will be detected when an open occurs on either the
sensor-power wire, the sensor (-V) wire, or the high-current portion of the
input sensor field device.
• an open on the input-signal wire or low-current portion of the input sensor
field device will not be detected, and will be seen as an off/inactive input
sensor field device.
• a shorted circuit from the sensor-power wire to sensor common (-V) is
detected as short fault (no voltage at the sensor-power port).
• a shorted circuit from the sensor-power wire to the input-signal wire
cannot be detected. It will appear as an on/active input device.
• a shorted circuit from the input-signal wire to sensor common (-V), with
the input sensor field device in the off-state, cannot be detected. It will
appear as an off/inactive input sensor device.
• a shorted circuit from the input-signal wire to sensor common (-V), with
the input sensor field device in the on-state, is detected as a short fault if
the sensor field device can pass the sensor power short circuit current.
• a shorted 3-wire input sensor device may or may not be detected,
depending on which portion of the input sensor device is shorted.
• a shorted circuit to the DIN rail or chassis ground cannot be detected.
Open OFF or ON OFF Red Red Open wire
and Module
No current in Sensor Power terminal-
Missing sensor, cut Sensor Power or Input Signal wire
Short OFF OFF Red Red Short and Module Shorted Sensor Power/ Common
OFF ON OFF Yellow None Shorted Sensor Power/ Input Signal
OFF OFF OFF OFF None Shorted Input Signal/ Common
ON OFF Red Red Short and Module
Shorted Input Signal/ Common
1
Reverse
User
Power
OFF or ON OFF Red OFF Reverse and
Module
User power supply wiring is reversed
1
If sensor can pass Sensor Power short circuit current
Fault Device/Input State Indicators Error Bit
Status
Conditions
Field
Device
Input
Status
Module
Fault
Channel
Fault
Open OFF OFF Red Red Open wire
and
Module
No current in Sensor Power terminal-
Missing sensor, cut Sensor Power or
Common wire
OFF or ON OFF OFF OFF None Cut Input Signal wire
Short OFF OFF Red Red Short and Module Shorted Sensor Power/ Common
OFF ON OFF Yellow None Shorted Sensor Power/ Input Signal
OFF OFF OFF OFF None Shorted Input Signal/ Common
ON OFF Red Red Short and Module
Shorted Input Signal/ Common
1
Reverse User Power OFF or ON OFF Red OFF Reverse and Module User power supply wiring is reversed
1
If sensor can pass Sensor Power short circuit current
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