30 2TLC172001M0211_A
6.2 Single channel systems
Instead of using two-channel systems some applications can be made failsafe by using the
principle of a dynamic single channel. By supplying electronic devices with dynamic signals a fault
in the electronics will lead to a static on or off state at the input which will be detected immediately.
By inverting the signal in or at the sensor, short circuits over the sensor are also detected.
Note: Serial connection is legal, but a short circuit of an even number of sensors is not
detected.
A direct connection between two terminals of IQ type is always detected. Detection of a short
circuit between an output of IQ and an input of I is not detected.
See 13.1 for maximum number of sensors that can be connected in series.
6.3 Emergency stop
When emergency stop functions remain inactivated for long periods of time, the function will
not be monitored. It is therefore strongly recommended that emergency stop systems are
periodically, manually tested and that this forms part of the maintenance instructions for the
machine.
Dyn. C
Dyn. A
Dyn. B
IQ_IQ_
IQ_
I_
IQ_
+ -
IQ_
I_
IQ_
I_
+ - Adam Eva
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