Siemens Simatic S7-200 System Manual page 54

S7-200 Programmable Controller System Manual
The S7-200 Allows You to Filter the Analog Inputs
The S7-200 allows you to select software filtering on individual analog inputs. The filtered value is the
average value 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 current value. This change, called the deadband, is specified in counts of the digital value
of the analog input.
The default configuration is to enable filtering for
all analog inputs.
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1. Select the View > Component >
System Block menu command and click
on the Analog Input Filters tab.
2. Select the analog inputs that you want to
filter, the number of samples, and the
deadband.
3. Click OK.
4. Download the modified system block to the
S7-200.
Tip
Do not use the analog filter with modules that pass digital information or alarm indications in the analog
words. Always disable analog filtering for RTD, Thermocouple, and AS-Interface Master modules.
The S7-200 Allows You to Catch Pulses of Short Duration
The S7-200 provides a pulse catch feature which can be used for some or all of the local digital input
points. The pulse catch feature allows you to capture high-going pulses or low-going pulses that are of
such a short duration that they would not always be seen when the S7-200 reads the digital inputs at the
beginning of the scan cycle. When pulse catch is enabled for an input, a change in state of the input is
latched and held until the next input cycle update. This ensures that a pulse which lasts for a short period
of time is caught and held until the S7-200 reads the inputs.
You can individually enable the pulse catch
operation for each of the local digital inputs.
To access the pulse catch configuration screen:
1. Select the View > Component >
System Block menu command and click
on the Pulse Catch Bits tab.
2. Click the corresponding check box and
click OK.
3. Download the modified system block to the
S7-200.
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Figure 4-25 Analog Input Filter
Figure 4-26 Pulse Catch
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