5
Functional description
Page 62
gas-lab
Q1
There are two different methods of avoiding fluttering messages:
1. Hysteresis monitoring (only in case of measurement monitoring)
A hysteresis can be defined to avoid fluttering messages if a measurement
fluctuates around a limit value. The message
<Hint limit begins>
will then
be generated or removed only if the measurement leaves the hysteresis
range.
measured
value
Lower hint limit
occurs
Lower hint limit
ends
Lower hint limit
Hysteresis
range
Upper hint limit
Hysteresis
range
Upper hint limit
ends
Upper hint limit
occurs
2. Considering a minimum pending time
When a minimum pending time is evaluated, a message is only considered
pending if the condition to be signalled (set digital input, hint limit violation,
etc.) is pending longer than the minimum pending time lasts.
The target of the message-processing concept is to combine messages in
groups. Owing to group monitoring and evaluation the monitoring itself remains
clearly understandable even if the amount of signals is rather large.
The user himself may define the scope of the associated error listing. Via the
device parameterisation he determines for each message whether a
single
message shall be entered in the error listing and logbook of the monitoring
module. Only if this is the case, the message will be entered in the error listing
as soon as it begins. There is no acceptance required for single messages; they
are automatically removed from the error listing when they end.