Festo CECX-X-C1 Series, Manual

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System manual CECX / Analog input/output module CECX-A-4E4A-V
CECX-II 21-13
21.6 Operating behavior
21.6.1 Response of the analog inputs
The input switch has a usable input voltage range of
±
10.4 V. The range
+10.0 V …+10.4 V or -10.4 V... -10.0 V can be used as saturation region.
The module returns concrete measurement values at the full input range of
±
10.4 V.
For sensor failure detection the input pins are fitted with expansion resis-
tance, which in case of an open input pin will bring the analog inputs to in-
put differential voltage of >10.4 V.
Once the upper transducer limit value has been reached through voltages
above 10.4 V the sensor failure bit will be set. If the lower transducer limit
value has been undercut the sensor failure bit will be automatically reset.
The expansion resistance (1 M
Ω
) allows the measure of approx. 30 V at
the analog inputs.
21.6.2 Behavior during a fault
21.6.2.1 Module errors
In case of a module error an internal watchdog monitor will be triggered. In
this case the outputs will be set to 0V, the module is reset and signals the
module error to the CPU module.
The CECX-A-4A-V module is no longer operative after a watchdog reset
and should therefore be replaced.
21.6.2.2 Sensor failure
In case of sensor failure the expansion resistance will bring the input to an
input difference voltage of > 10.4 V.
The sensor failure is communicated to the CPU.
Once the sensor failure has been corrected the status "Sensor failure" will
be automatically reset.