Omron NX-IA3117, User Manual

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4 Installation and Wiring
4 - 38 NX-series Digital I/O Unit User’s Manual (W521)
 Precautions when Connecting a Two-wire DC Sensor
When a two-wire sensor is used with a DC Input Unit, check that the following conditions are met.
Failure to meet these conditions may result in operating errors.
(a) Relation between ON voltage of the DC Input Unit and sensor residual voltage
The DC Input Unit cannot detect sensor output ON unless the following conditions are satisfied:
V
ON
≤ V
CC
- V
R
The voltages related to the conditions for NPN type sensors are shown in the figure below.
The voltages related to the conditions for PNP type sensors are shown in the figure below.
V
CC
: Power supply voltage
V
R
: Sensor's output residual voltage
V
ON
: ON voltage of DC Input Unit
IN
IOG
IOV
IOG
IOV
V
R
V
CC
V
ON
Two-wire sensor
DC Input Unit
Communications Coupler Unit or
Additional I/O Power Supply Unit
IOG
IOV
IOG
IOV
IN
V
R
V
CC
V
ON
Two-wire sensor
DC Input Unit
Communications Coupler Unit or
Additional I/O Power Supply Unit