Siemens Simatic S7-400 - Manual (Page 252)

Analog Modules
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S7-400, M7-400 Programmable Controllers Module Specifications
A5E00069467-07
Basic Execution Time of the Analog Input Channels
The basic execution time corresponds to the cycle time for all the enabled
channels.
Setting the Smoothing of Analog Values
You can set the smoothing of the analog values in STEP 7 for some analog input
modules.
Using Smoothing
Smoothing of analog values ensures a stable analog signal for further processing.
It makes sense to smooth the analog values with slow variations of measured
values – for example, with temperature measurements.
Smoothing Principle
The measured values are smoothed by digital filtering. Smoothing is accomplished
by the module calculating average values from a defined number of converted
(digitized) analog values.
The user assigns parameters to smoothing at not more than four levels (none, low,
average, high). The level determines the number of analog signals used for
averaging.
The higher the smoothing level chosen, the more stable is the smoothed analog
value and the longer it takes until the smoothed analog signal is applied after a
step response (refer to the following example).