Rockwell Automation Publication ICSTT-RM406J-EN-P - February 2021 51
Chapter 6
Troubleshooting and Rectifying Channel/Field
Faults
This chapter provides recommended approaches to find and repair channel/
field faults. It must be read in conjunction with the local operation and
maintenance manual or equivalent documentation for your system.
Understanding the State
Variable
(<variablename>.STA)
The state variable (<variablename>.STA) is one attribute of the full structure
for input and output channels. The variable reports a numeric value which
reflects the current state of the channel.
There are seven possible values (states) for the state variable from 1 to 7. States
2 and 4 show normal operation for digital inputs and outputs; state 3
represents normal operation for an analogue input. The other states show a
fault.
The state variable updates in real time. The fault diagnosis procedures for field
faults use the value of the state variable.
Correlation of Status Indicators with State Variable for a Digital Input
A digital input channel without line monitoring can find and report states 2, 3,
4, 6 and 7, but cannot find an open circuit or short circuit. A line monitored
input can find and report every state, including an open circuit or short circuit.
ARC FLASH HAZARD: : If you connect or disconnect wiring, modules, or
communications cabling while power is applied, an electrical arc can
occur. This could cause an explosion in hazardous location installations. Do
not remove wiring, fuses, modules, or communications cabling while circuit
is energized unless the location is known to be non-hazardous. Failure to
follow these instructions can cause injury.
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