
Analog modules
5.21 Analog input module SM 431; AI 8 x 14 Bit (6ES7431-1KF20-0AB0)
S7-400 Automation System Module Data
280 Reference Manual, Edition 09/2009, A5E00850736-06
Measured value smoothing
You will find information that is generally applicable to the smoothing of analog values in the
respective section. You can only set strong smoothing for the SM 431; AI 8 x 14 Bit.
The module cycle time is a constant, irrespective of how many channels are enabled. It
therefore has no effect on the filter settling time, which is defined by the parameter
assignment of interference frequency suppression and smoothing.
Filter settling time with strong smoothing
Table 5- 54 Interference frequency suppression and filter settling time with smoothing
Noise suppression Smoothing Filter settling time in ms
None Strong -
50 Hz Strong 100
60 Hz Strong 83,333
400 Hz Strong 12,5
Step response with strong smoothing
The following figure illustrates the contents of the table above. It shows the filter settling time
after which, in the case of a step response, the smoothed analog value is applied to
almost 100%, depending on the interference frequency suppression that has been set. The
figure applies to every change of signal at an analog input.
50
100
0
63
60 Hz:
50 Hz:
12030 15060
12,5 83,333 100
400 Hz:
Signal variation
in percent
Step response for any analog input signal
Noise suppression
Filter settling time in ms
Figure 5-30 Step response of the SM 431; AI 8 x 14 Bit (6ES7 431-1KF20-0AB0)
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