
Input and Output Connections
24
AC-425x-B Hardware Installation and User Manual
4.1.5
Normally Closed Supervised Single EOL Resistor Input Connection
Connect a 2.2 k
Ω
resistor in series to the input switch contacts.
A Normally Closed Supervised Input has 3 states:
Switch Closed – Normal State:
Loop resistance = 2.2 k
Ω
Switch Open – Abnormal State:
Loop resistance = Infinite (open circuit)
Short circuit across input terminals – Trouble State:
Loop resistance = 0 (short circuit)
Figure 14: Normally Closed Supervised Input (Single Resistor)
4.1.6
Normally Closed Supervised Double EOL Resistor Input Connection
Connect a 2.2 k
Ω
resistor in series to the input switch contacts.
Connect an 8.2 k
Ω
resistor parallel to the input switch contacts.
A Normally Closed Supervised Input has 3 states:
Switch Closed – Normal State:
Loop resistance = 2.2 k
Ω
Switch Open – Abnormal State:
Loop resistance = 10.4 k
Ω
Open circuit (infinite loop resistance) or short circuit (0 resistance) across input terminals
– Trouble State