Lenze 8400 - Manual (Page 275)

Safety engineering
Basics for safety sensors
10
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275 EDS84ASC552 EN 9.1
10.4 Basics for safety sensors
The components used must comply with the control category required for the application.
Passive sensors
Passive sensors are two-channel switching elements with contacts. The connecting cables
and the sensor function must be monitored.
The contacts must switch simultaneously (equivalently). Nevertheless, safety functions
will be activated as soon as at least one channel is switched.
The switches must be wired according to the closed-circuit principle.
Examples of passive sensors:
ƒ Door contact switch
ƒ Emergency stop control units
Active sensors
Active sensors are units with 2-channel semiconductor outputs (OSSD outputs). With the
integrated safety system of this device series, test pulses < 1 ms for monitoring the
outputs and cables are permissible. The maximally permissible connection capacity of the
outputs is to be observed. Active sensors are wired directly to the terminals of the
integrated safety system. Monitoring for cross or short circuits must be carried out by the
active sensor.
P/M-switching sensors switch the positive and negative cable or the signal and ground
wire of a sensor signal.
The outputs must switch simultaneously (equivalently). Nevertheless, safety functions
will be activated as soon as at least one channel is switched. Active triggering of only one
channel indicates faulty sensors or impermissible wiring.
Examples of active sensors:
ƒ Lightgrid
ƒ Laser scanner
ƒ Control systems