Omron GX-AD0471, User Manual, Page: 380 / 394

A Appendix
A - 76 GX-series EtherCAT Slave Unit User’s Manual
A-3 Precautions with Connecting
Two-wire DC Sensors
When using a two-wire DC sensor with a DC input type Slave Unit, check that the following conditions
have been met. Failure to meet these conditions may result in operating errors.
V
ON
≤
V
CC
- V
R
V
CC
: I/O power supply voltage (The allowable power supply voltage range is 20.4 to 26.4 V, so 20.4 V will be
used here to allow for the worst possible conditions.)
V
ON
: ON voltage for a Unit with DC inputs
V
R
: Sensor's output residual voltage
It is sometimes possible to satisfy the above equation by adjusting the I/O power supply voltage (V
CC
)
to 26.4 V.
I
OUT
(min)
≤
I
ON
≤
I
OUT
(max)
I
OUT
: Sensor control output (load current)
I
ON
: ON current of a Unit with DC inputs
I
ON
is calculated as follows:
I
ON
= (V
CC
- V
R
- V
F
) / R
IN
V
F
: Internal residual voltage of a Unit with DC inputs
R
IN
: Input impedance of a Unit with DC inputs
When I
ON
is smaller than I
OUT
(min), connect a bleeder resistor R.
The bleeder resistor constant can be calculated using the following equation.
R
≤
(V
CC
- V
R
) / (I
OUT
(min) - I
ON
)
Power W
≥
(V
CC
−
V
R
)
2
/ R
×
4 [allowable margin]
A-3-1 Relation between ON Voltage of a Unit with DC Inputs and Sensor
Residual Voltage
A-3-2 Relation between ON Current of a Unit with DC Inputs and Sensor
Control Output
2-wire
sensor
DC input
type slave
R
IN
V
R
R
V
CC