Set data clipping options for tag data

Before you screen tag values, you can specify a valid range for tag values and clip incoming tag data to values within the specified range or ignore values that fall outside of the range.

In the Read/Write External Data window, you can set the Min and Max value for a tag. The If Under Min and If Over Max selections then determine how the software clips the data if the incoming tag values are less than or greater than the specified Min and Max values, respectively. Typically, the Min and Max values represent physical or process-related constraints on the tag values. For example, a valve that cannot open more than 80% for safety reasons should have a Max value of 0.80 on its Pos variable.

Set data clipping options for a tag

1. Open the External Data Manager.

2. Select the tag collection that contains the tags that you want to set data clipping options for, and then select Transfer.

   The Read/Write External Data window appears.

3. In the Tag List section, in the Min and Max columns, enter the minimum and maximum values for the tag data, respectively.

   If you leave the Min and Max value blank, the software does not apply any data clipping for the tag data.

   

4. In the If Under Min and If Over Max lists, select the action that the software should take if the tag value is outside the Min or Max value, respectively.

   • Clip: Set the Screened Value to the Minimum value or Maximum value, respectively.

   • Use Last Good Value: Set the Screened Value to the Last Good Value.

   • Report Error: Leave the Screened Value blank. In addition, the system logs an error, but currently does not display the error in the Log pane.

   • Do Nothing: Leave the Screened Value blank.

   The next time you screen tag values, the software clips the data according to your specifications.