Limit monitoring
9.2 Influence of hysteresis and delay time on limit monitoring
Analog input module AI Energy Meter 480VAC/CT HF (6ES7134-6PA00-0CU0)
78 Manual, 07/2018, A5E42674880-AA
Hardware interrupt at a limit violation
The hardware interrupt provides the following information:
● Measured value ID of the monitored measured or calculated variable
● Number of the limit (0 = Limit 1. 15 = Limit 16)
● Information on whether limit was exceeded or fallen below
For more detailed information, refer to section Hardware interrupts (Page 110).
Changing properties in RUN
The following table shows the supported control information:
Enable/disable monitoring per limit
1
Disabled Module version with 20 bytes of output
Reset number of total limit violations 0 Module version starting at 2 bytes of
output data
1
Effective only with enabled gate
Influence of hysteresis and delay time on limit monitoring
Delay time and hysteresis
In order to prevent the triggering of limit violations with small fluctuations, you have the
following configuration options in STEP 7:
● Delay time in seconds (0 to 10 s)
With the delay time, you filter faults and thereby prevent limit value monitoring from
triggering too frequently. The limit violation is counted only when the limit violation is
present for longer than the configured delay time. The delay time is also taken into
consideration with an outgoing limit violation, directly after a high or low limit has been
violated in the permitted range. If the measured variable lies between limit violation and
hysteresis after the limit violation has been corrected again, the delay time expires also
without leaving the hysteresis.
● Hysteresis as a percentage (0 to 20%)
With the hysteresis, you suppress fluctuations around the limit. The hysteresis is a
tolerance range that you define as a percentage deviation of the configured limit. The limit
violation is considered to be corrected only when the monitored value leaves the
tolerance range.
Note
You can get information about underflow and overflow from the calculation of
minimum
243) and maximum values (Page 237) of selected measured variables.
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