Threshold Value Trigger - Siemens S7-1200 Operating Instructions Manual

Configuration and operation
4.15 STEP 7 configuration of individual parameters
Analog inputs that are configured as an event are processed on the CP in the following
sequence:
Sequence of analog value processing
1. Reading the data from the input area of the CPU
2. Analog value preprocessing (part 1)
Processing involves the following steps:
– Mean value generation
– Unipolar transfer (if configured)
– Error suppression time (if configured)
– Smoothing (if configured)
3. Threshold value calculation (if Threshold value trigger is configured)
4. Analog value preprocessing (part 2)
– Set limit value 'low' / Set limit value 'high' (if configured)
5. Storage of the value in the send buffer
Transfer of the value to the partner if trigger and threshold value conditions are met.
4.15.7.3

Threshold value trigger

The CP calculates the value for the threshold value trigger after the analog value
preprocessing, refer to the section Analog value preprocessing (Page 79).
Threshold value trigger: How the integrattion calculation works
To calculate the threshold value trigger, the integration method is used.
In the integration threshold value calculation, it is not the absolute value of the deviation of
the process value from the last stored value that is evaluated but rather the amount of the
integrated deviation.
The calculation cycle
The integration threshold value calculation works with a cyclic comparison of the integrated
current value with the last stored value. The calculation cycle in which the two values are
compared is 500 milliseconds.
(Note: The calculation cycle must not be confused with the scan cycle of the CPU memory
areas).
The deviations of the current process value are totaled in each calculation cycle. The trigger
is set only when the totaled value reaches the configured value of the threshold value trigger
and a new process value is entered in the send buffer.
78
- if configured: Calculation and then continue at point 4.
- if not configured: Continue with "Unipolar transfer".
Operating Instructions, 01/2015, C79000-G8976-C381-01
CP 1243-7 LTE