Analog Input Filter - Siemens SIMATIC S7-200 System Manual

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
Port(s)
Analog Input Filters
AIW 0
AIW 2
Filtered value is the
AIW 4
average value of the
sum of this number of
AIW 6
samples.
Number of samples
64
Configuration parameters must be downloaded before they take effect.
Not all PLC types support every System Block option. Press F1 to see
which options are supported by each PLC.
Figure 6-9
S7-200 Programmable Controller System Manual
A5E00066097-02
Retentive Ranges Password
Pulse Catch Bits
Select which Analog Inputs to filter
8 16
10 18
12 20
14 22
Analog Input Filter
CPU and Input/Output Configuration
Output Table
24 32 40
26 34 42
28 36 44
30 38 46
Deadband (16 - 4080)
320
0 = Deadband Disabled
OK
Input Filters
Background Time
Defaults
48 56
50 58
52 60
54 62
Cancel
6-9