Siemens SIMATIC S7-400 Reference Manual page 197

Use of 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 mean values, derived from a defined number of converted (digitized) analog
values.
The user assigns parameters to smoothing with a maximum of four levels (none, weak,
medium, strong). The grade determines the number of analog signals used for averaging.
A higher smoothing provides a more reliable analog value, and prolongs the time it takes to
apply a smoothed analog signal following a step response (see the example below.)
Example
The figure below shows the number of cycles a module requires to apply an almost 100%
analog value after a step response, based on the smoothing function settings. The figure
applies to all signal changes at the analog input.
Signal variation in
percent
Smoothing
Figure 5-3
Further information on smoothing
For information showing whether a specific module supports smoothing functions, and special
features to observe, refer to the section dealing with the analog input module.
S7-400 Automation System Module Data
Reference Manual, Ausgabe 11/2016, A5E00850736-08
5.7 Conversion, cycle, settling and response time of analog modules
Step response for any analog input signal
100
63
50
0
50
Low:
average:
high:
Example of the effect of smoothing on step responses
150
100
Module cycles
Analog modules
200
197