Omron NX-ID3343 User Manual page 106

4 Installation and Wiring
 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 ≤ V - V
ON CC
The voltages related to the conditions for NPN type sensors are shown in the figure below.
Two-wire sensor
The voltages related to the conditions for PNP type sensors are shown in the figure below.
Two-wire sensor
V : Power supply voltage
CC
V : Sensor's output residual voltage
R
V : ON voltage of DC Input Unit
ON
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R
V V
CC ON
V
R
V V
R CC
V
ON
IOV
Communications Coupler Unit or
Additional I/O Power Supply Unit
IOG
IOV
IN
DC Input Unit
IOG
IOV
Communications Coupler Unit or
Additional I/O Power Supply Unit
IOG
IOV
DC Input Unit
IN
IOG
NX-series Digital I/O Unit User's Manual (W521)