Input Filters Tab (Analog) - System Block Configuration

View the System Block to set up CPU options by using one of the following methods:

·Click the System Block button on the Navigation Bar.

·Select the View > System Block menu command.

·Click on the System Block icon in the Instruction Tree.

Click on the Analog Input Filters tab to set properties. Enter new properties and then download the modifications to the CPU.

With the CPU 222, CPU 224, CPU 226, and CPU 226XM, 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 dead band) 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.


Analog filtering should not be used with modules that pass digital information or alarm indications in the analog words. The ASi Master Module, Thermocouple Module, and RTD Module require that CPU Analog Input Filtering is disabled.

The default System Block setting for Analog Input Filtering is ON (checked). You must disable filtering (uncheck) all associated Analog Inputs and download the modified System Block to operate these I/O modules.

See Also:

System Block

Application User Reference

Getting Started Contents