Input and Output Connections
AC-225x-B Series Hardware Installation and User Manual 21
4.1.2 Normally Closed Input Connection
Normally Closed Input has two states:
▪ Switch Closed – Normal State:
Loop resistance = 0 (short circuit).
▪ Switch Open – Abnormal State:
Loop resistance = Infinite (open circuit).
Figure 11: Normally Closed Input Connection
4.1.3 Normally Open Supervised Single Resistor Input Connection
Connect an 8.2 kΩ resistor in parallel to the input switch contacts.
Normally Open Supervised Input has 3 states:
▪ Switch Open – Normal State:
Loop resistance = 8.2 kΩ
▪ Switch Closed – Abnormal State:
Loop resistance = 0 (short circuit).
▪ Open circuit across input terminals – Trouble State:
Loop resistance = Infinite (open circuit).
Figure 12: Normally Open Supervised Input Connection (Single Resistor)
4.1.4 Normally Open Supervised Double Resistor Input Connection
Connect a 2.2 kΩ resistor in series to the input switch contacts.
Connect an 8.2 kΩ resistor parallel to the input switch contacts.
Normally Open Supervised Input has 3 states:
▪ Switch Open – Normal State:
Loop resistance = 10.4 kΩ
▪ Switch Closed – Abnormal State:
Loop resistance = 2.2 kΩ
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