User manual

62
Cautions when using 2 wired type
Use a breeder resistor as below when the leakage current from 2 wired
type photoelectric switch or proximity switch keeps flowing into the
PLC.
DC 12-24V type input unit
(OFF voltage 2.5V, input impedance 3
KΩ)
2 wired sensor
DC input unit
Since the OFF voltage of input is 2.5V, determine the R
value to set the voltage between COM terminal and input
terminal to be 2.5V or less.
Input impedance is 3
KΩ
For the resistor, W can be calculated as follows:
(Power supply voltage)
2
W =
R
Use 3 to 5 times larger value .
Breeder
resistor
Internal Circuit
Input
terminal
COM
terminal
7. 5
R
≤ (KΩ)
3I-2.5
3R
I x ≤ 2.5,
3 + R
I: Leakage current (mA)
R: Breeder resistance (KΩ)