Omron DRT2 Series Operation Manual page 270

Precautions with Connecting Two-wire DC
When using a two-wire Sensor with a Slave using transistor inputs, check that the following conditions have
been met.
Failure to meet these conditions may result in operating errors.
Relation between ON Voltage of Slave with Transistor Inputs
and Sensor Residual Voltage
≤ V − V
V
ON CC R
V : I/O power supply voltage (The allowable power supply voltage range is 20.4 to 26.4 V, so 20.4 V will be
CC
used here to allow for the worst possible conditions.)
− : ON voltage for a Slave with Transistor Inputs
V
ON
V : Sensor's output residual voltage
R
It is sometimes possible to satisfy the above equation by adjusting the I/O power supply voltage (V
26.4 V.
Relation between ON Current of Slave with Transistor Inputs
and Sensor Control Output (Load Current)
(min) ≤ I ≤ I
I
OUT ON OUT
I : Sensor control output (load current)
OUT
I : Slave ON current
ON
− V − V
I = (V )/R
ON CC R F
V : Internal residual voltage of a Slave with Transistor Inputs
F
R : Input impedence of a Slave with Transistor Inputs
IN
When I is smaller than I
ON
The bleeder resistor constant can be calculated using the following equation.
R ≤ (V − V (min.) − I
)/(I
CC R OUT
Power W ≥ (V − V 2
)
CC R
2-wire
V
Sensor R
V
CC
Appendix E
(max.)
IN
(min), connect a bleeder resistor R.
OUT
)
ON
/R × 4 [allowable margin]
Slave with
Transistor
R R
IN
Input
Sensors
) to
CC
253