Rockwell Automation Publication ICSTT-RM448M-EN-P - February 2021 89
Chapter 5 Install the AADvance System
Field Loop Circuit for Line Monitored Digital Input for Fire and Gas Systems (F & G)
• The F&G circuit will also allow two devices to be in alarm without
reporting short circuit.
• All of the input circuits are suitable for simplex, dual and TMR
configurations.
• The F&G circuit assumes that the devices are volt-free contacts.
• For further information, please refer to application note AN-T90001
Field
Loop Configuration, which is located in the Rockwell Automation
Knowledgebase Support Center. This also includes advice for fire
detectors which are not simple volt free contacts.
Digital Input Slew Tolerance
It is possible during sustained periods of abnormal input voltage slewing that
channels can be declared faulted as a consequence of diagnostics otherwise
designed to verify that the channels are operating within their designed safety
accuracy.
To avoid spurious declaration of channel faults it is necessary to ensure that
the input signal condition satisfies the maximum slew rate criteria defined in
the Solutions Handbook. Accordingly it may be necessary to condition the
input signal such as by filtering or by appropriate choice of process safety time.
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