Discrepancy Time - WAGO 753-668/000-004 Manual

WAGO-I/O-SYSTEM 750
753-668/000-004 4FAI 0/4-20 mA Diff PROFIsafe
4.8

Discrepancy Time

If there is a discrepancy, the unit value is set to substitute value.
If there is a discrepancy after switching on or after an acknowledgment, unit
value 2 is set to the configured substitute value, as no valid process value exists
previously. The status of both channels of the channel pair is 1.
During the cyclical check of the input measured values for two-channel use, the
time period during which the input measured values of a channel pair may
deviate outside the set tolerance window can be defined. If one channel of a
channel pair leaves the tolerance window, it is in discrepancy mode and the time
measurement of the discrepancy time is started. Meanwhile, the process value is
kept at the last valid process value before discrepancy operation starts. If a
deviation outside the set tolerance window continues to be detected after the
discrepancy time has expired, the error "Discrepancy time exceeded" is reported
and both affected input channels are passivated. The error must be
acknowledged, see Section "Diagnostics".
If the input measured values no longer deviate outside the set tolerance, the
channel status and process value are updated. The F I/O module is then in
normal operation again.
The settings are made via the "Discrepancy Time" parameter, which is
described in Section "Commissioning" > ... > "Setting Parameters".
In case of channel error, two-channel evaluation is aborted.
If a channel error occurs, the two-channel evaluation is aborted. The process
values of the two channels of the channel pair are transferred to the process
image as in single-channel operation.
The following parameters must also be set:
•
Sensor evaluation
•
Tolerance window
•
Relative tolerance and/or
•
Absolute tolerance
Version 1.0.0, valid from HW/SW Version 01/01
Functions 59
Manual