CPU and Input/Output Configuration
6-9
S7-200 Programmable Controller System Manual
A5E00066097-02
6.5 Analog Input Filter
With the CPU 222, CPU 224, and CPU 226 you can select software filtering on
individual analog inputs. The filtered value is the average value of the sum of a
preselected number of samples of the analog input. The filter specification (number
of samples and deadband) is the same for all analog inputs for which filtering is
enabled.
The filter has a fast response feature to allow large changes to be quickly reflected
in the filter value. The filter makes a step function change to the latest analog input
value when the input exceeds a specified change from the average value. This
change is called the dead band, and is specified in counts of the digital value of the
analog input.
Note
Analog filtering should not be used with modules that pass digital information or
alarm indications in the analog words. Use the screen shown in Figure 6-9 to
disable analog filtering for RTD, Thermocouple, and AS-Interface Master modules.
To access the analog input filter, select the menu command View > System Block
and click on the Analog Input Filters tab. Select the analog inputs that you want to
filter and click OK. See Figure 6-9. Default STEP 7-Micro/WIN 32 analog input filter
configuration is enabled for all inputs.
System Block
OK Cancel
Configuration parameters must be downloaded before they take effect.
PasswordPort(s) Retentive Ranges
Analog Input Filters
Output Table Input Filters
Pulse Catch Bits
Background Time
AIW 0
AIW 2
8
10
16
18
24
26
32
34
40
42
48
50
56
58
N
umber of samples
Deadband (16 - 4080)
0 = Deadband Disabled
64
320
Not all PLC types support every System Block option. Press F1 to see
which options are supported by each PLC.
Defaults
12
14
20
22
28
30
36
38
44
46
52
54
60
62
AIW 4
AIW 6
Select which Analog Inputs to filter
Filtered value is the
average value of the
sum of this number of
samples.
Figure 6-9 Analog Input Filter
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