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Wiring Precautions Section 3-6
• The circuit below should NOT be used for I/O devices having a voltage
output.
Precautions when
Connecting a Two-wire DC
Sensor
When using a two-wire sensor with a 24-V DC input device, check that the fol-
lowing conditions have been met. Failure to meet these conditions may result
in operating errors.
1,2,3... 1. Relation between the FQM1 ON voltage and the sensor residual voltage:
V
ON
≤ V
CC
– V
R
2. Relation between the FQM1 ON current and sensor control output (load
current):
I
OUT
(min) ≤ I
ON
≤ I
OUT
(max.)
I
ON
= (V
CC
– V
R
– 1.5 [FQM1 internal residual voltage])/R
IN
If I
ON
is smaller than I
OUT
(min), connect a bleeder resistor R. The bleeder
resistor constant can be calculated as follows:
R
≤ (V
CC
– V
R
)/(I
OUT
(min.) – I
ON
)
Power W
≥ (V
CC
– V
R
)
2
/R × 4 [allowable margin]
IN
7 mA
0 V
+
COM
+
IN
COM
7 mA
0 V
+
IN
COM
0 V
+
+
Output
Output
Output
NPN current output
PNP current output
Voltage output
Sensor
power
supply
Sensor power
supply
Sensor
power
supply
DC input
DC input
DC input
Current
regulator
+
IN
0 V
+
COM
−
Sensor
power
supply
DC input
Output