Principle of change-over contact diagnostics
If the digital inputs of a channel group are configured as "change-over contacts", the module for
this channel group carries out diagnostics for the change-over contact encoder type.
If the plausibility check is negative, the following happens:
• The module identifies the value status of the NO channel as "invalid" (QI = "0").
• The module creates a diagnostics entry for the NO channel.
• If the change-over contact error diagnostics is enabled, a diagnostic interrupt is triggered.
The digital input signal and the value status are only updated for the NO channel. The digital
input signal is 0 and the value status is "invalid" (QI = "0") for the NC channel. This channel is only
used for a validity check of the sensor.
Special features
Please note the following special features for change-over contact diagnostics:
• If the normally open and normally closed contact signals are not plausible after 300 ms, a
change-over error is output as diagnostics information.
• If there is already a fault (QI = 0, e.g. a wire break), the module will no longer perform
diagnostics for change-over errors.
• There are different diagnostics options depending on the type of change-over contact.
Depending on the encoder type, a change-over error can have different causes.
– In the case of connected change-over contacts, a change-over error may also be the result
– In the case of unconnected change-over contacts, a change-over error may also be the
– If a wire break or short-circuit can be detected with the particular encoder type but its
DI 16xNAMUR HA
Equipment Manual, 08/2019, A5E39293880-AD
7.4 Useful information about diagnostics for the change-over contact encoder type
of a short-circuit (encoder is not defective; there is a short-circuit).
result of a wire break.
diagnostics is not enabled, instead of the wire break or short-circuit diagnostics
information, the change-over error diagnostics information is displayed if this is enabled.
Displays and interrupts
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