Rockwell Automation AADvance Controller Safety Manual - Manual (Page 70)

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4-14 Document: 553630
ICSTT-RM446K-EN-P Issue: 10 _C
Safety Manual (AADvance Controller)
 Minimum Isolation is 0.75M  between the field loop conductors.
 These values will allow the input to detect more accurately different
voltage levels that represent OPEN CCT - OFF - ON - SHORT CCT and
will also detect Over Voltage and an input which is neither ON or OFF.
The values ensure that a line fault will be declared before it becomes
possible for a false declaration of On and Off states due to a combination
of resistor value drift and loop voltage variation.
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. This also includes advice for fire detectors which are
not simple volt free contacts.