
11
SICK8 007 755.0300
DC 3/4-wire sensors
Apart from the oscillator, direct-
current sensors also have an output
amplifier. They are supplied as 3/4-
wire sensors with NO, NC,
complementary or programmable
outputs. Sensors of this type have
short-circuit, reverse-polarity
protection, and power-up pulse
suppression. The residual current is
negligable. A capacitive load of up to
0.15 µF can be connected. These
sensors are supplied as:
- NC, negative-switching (NPN)
- NC, positive-switching (PNP)
- NO, negative-switching (NPN)
- NO, positive-switching (PNP)
- programmable NO/NC,
negative-switching (NPN)
- programmable NO/NC,
positive-switching (PNP)
- complementary NO and NC
negative-switching (NPN)
- complementary NO and NC
positive-switching (PNP)
- free configurable as
NO, negative-switching (NPN)
NO, positive-switching (PNP)
NC, negative-switching (NPN)
NC, positive-switching (PNP)
These points are particularly relevant
in the case of parallel and serial
connections. These sensors are
supplied as:
-normally open
-normally closed
-programmable NO/NC
Serial connection
of 2-wire sensors:
Not recommended
Parallel connection of 2-wire sensors:
In the case of parallel connection, the
residual currents of all proximity
sensors are added together.
Glossary
Electrical
Serial connection of 3-wire sensors:
With series connection, the voltage
drops and the standby delay times of
the individual proximity sensors are
added together.
That is the reason for a reduced load
voltage.
PNP-connection:
Sensor n
Sensor 1
0V
+Ub
Parallel connection of 3-wire sensors:
The LEDs of all proximity sensors light
up if only one sensor is active. It is
therefore advisable to install blocking
diodes in the switching output.
PNP-connection:
+Ub
0V
Sensor 1 Sensor n
AC/DC 2-wire sensors
Apart from the oscillator, alternating
current 2-wire sensors also have a
transistor as an output amplifier.
These sensors are directly operated
in series with the load. As a result, a
small residual current flows across
the load when the sensors are
disabled. In forced-tripping mode, a
drop in voltage also occurs at the
sensor.
Protection class
Sensors not bearing the symbol
must be operated at power sources
which comply with the safety require-
ments for extra-low voltage as per
VDE 100.
L1/+
Sensor 1 Sensor n
N/-