Safety engineering
Overview of sensors
10
l
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EDS84ASC552 EN 8.1
10.3 Overview of sensors
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−off 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.
P/M−switching sensors switch the positive and negative cable or the signal and ground
wire of a sensor signal.
The outputs have to switch simultaneously. Nevertheless, safety functions are triggered
as soon as at least one channel is switched.
Examples of active sensors:
ƒ Lightgrid
ƒ Laser scanner
ƒ Control systems
Sensor inputs
For unused sensor inputs, "Input deactivated" must be parameterised.
Connected deactivated sensors can create the false impression of safety technology being
provided. For this reason, a deactivation of sensors by parameter setting only is not
permissible and not possible. It is monitored that no sensor signal is pending.
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