Precautions When Connecting A Two-Wire Dc Sensor - Omron CP1L-EL20DR-D Operation Manual

Wiring CP1L-EL/EM CPU Units
Precautions when
Connecting a Two-wire DC
Sensor
1,2,3...
When using a two-wire sensor with a 24 VDC input device, check that the fol-
lowing conditions have been met. Failure to meet these conditions may result
in operating errors.
1. Relation between voltage when the PLC is ON and the sensor residual
voltage:
≤ V − V
V
ON CC R
2. Relation between current when the PLC is ON and sensor control output
(load current):
(min) ≤ I ≤ I
I
OUT ON OUT
− V − 1.5 [PLC internal residual voltage]*)/R
I = (V
ON CC R
When I is smaller than I
ON
bleeder resistor constant can be calculated as follows:
R ≤ (V − V
)/(I
CC R OUT
Power W ≥ (V − V
CC
3. Relation between current when the PLC is OFF and sensor leakage cur-
rent:
≥ I
I
OFF leak
Connect a bleeder resistor if I
equation to calculate the bleeder resistance constant.
R ≤ R × V
/(I
IN OFF leak
Power W ≥ (V − V
CC
Two-wire Sensor
Vcc: Power voltage
Von: PLC ON voltage
Voff: PLC OFF voltage
Ion: PLC ON current
Ioff: PLC OFF current
Rin: PLC input impedance
4. Precautions on Sensor Inrush Current
An incorrect input may occur due to sensor inrush current if a sensor is
turned ON after the PLC has started up to the point where inputs are pos-
sible. Determine the time required for sensor operation to stabilize after the
sensor is turned ON and take appropriate measures, such as inserting into
the program a timer delay after turning ON the sensor.
(max)
(min), connect a bleeder resistor R. The
OUT
(min) − I
)
ON
2 /R × 4 [allowable margin]
)
R
is greater than I
leak
× R − V
)
IN OFF
2
/R × 4 (allowable margin)
)
R
R
V R
IN
R
V
CC
Vr: Sensor output residual voltage
Iout: Sensor control output (load current)
Ileak: Sensor leakage current
R: Bleeder resistance
Section 3-4
IN
. Use the following
OFF
DC Input Unit
85