Input and Output Connections
32
AC-825IP Hardware Installation and User Guide
Figure 24: Normally Closed Input Connection
4.1.3
Normally Open Supervised Single EOL Resistor Input
Connection
Connect an 8.2 k
Ω
resistor in parallel to the input switch contacts.
A Normally Open Supervised Input has 3 states:
Switch Open – Normal State:
Loop resistance = 8.2 k
Ω
Switch Closed – Abnormal State:
Loop resistance = 0 (short circuit)
Open circuit across input terminals – Trouble State:
Loop resistance = Infinite (open circuit).
Figure 25: Normally Open Supervised Input (Single Resistor)
4.1.4
Normally Open 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 Open Supervised Input has 3 states:
Switch Open – Normal State:
Loop resistance = 10.4 k
Ω
Switch Closed – Abnormal State:
Loop resistance = 2.2 k
Ω
Open circuit (infinite loop resistance) or short circuit (0 resistance) across
input terminals – Trouble State
