Omron NX-IA3117, User Manual

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4 Installation and Wiring
NX-series Digital I/O Unit User’s Manual (W521)
4
-4 Wiring
E
x
amp
les
4
4-
4-1 Wiring the Inpu
t Unit
s
(b) Relation between input current to the DC Input Unit and sensor control output (load current)
The DC Input Unit cannot detect sensor output ON unless the following conditions are satisfied:
I
OUT
(min) ≤ I
in
≤ I
OUT
(max)
I
OUT
(min): Minimum value of load current
I
OUT
(max): Maximum value of load current
Use the following equation to calculate the input current of the resistance input.
I
in
= (V
CC
- V
R
- 1.5 [internal residual voltage of DC Input Unit]) / R
IN
Use the following equation to calculate the input current of the constant current input.
I
in
= I
ON
Note For constant current input type Input Units, the input current does not increase linearly for the input volt-
age. If you gradually raise the input voltage and once the input current reaches I
ON
, the input current
does not increase and remains roughly constant even when the input voltage is raised.
When I
in
is smaller than I
OUT
(min), connect a bleeder resistor R. The bleeder resistor constant can
be calculated as follows: Select an appropriate bleeder resistor R so that both equations can be sat-
isfied.
R ≤ (V
CC
- V
R
) / (I
OUT
(min) - I
ON
)
Rated power W of bleeder resistor ≥ (V
CC
- V
R
)
2
/ R × 4 [allowable margin]