Tag deadbands

A deadband is a sensitivity setting for tag values. A deadband is usually associated with I/O tags whose values change constantly. A deadband filters out small momentary changes in a tag value to reduce the amount of InTouch data processing.

The Tagname Dictionary includes two deadband properties for tags associated with integer and real data.

• Value Deadband: The value deadband property sets a threshold that must be exceeded before WindowViewer refreshes the tag’s value in run-time memory. The following figure shows the absolute deadband range around a current tag value.

  

• Log Value Deadband: The log deadband sets a threshold that must be exceeded before the tag’s value is written to the log file. The following figure shows the deadband around the current value of a logged tag.

  

  Only new tag values outside of the deadband are written to the log file. Small value changes within the deadband range are ignored and not logged.

Set a tag deadband

1. Open the Tagname Dictionary dialog box.

2. Choose Select. The Select Tag dialog box appears. The tags currently defined for the application are listed.

3. Select an integer or real tag type from the list.

4. Select OK. The detail portion of the Tagname Dictionary dialog box shows additional options when you select a real or integer tag.

   

5. Set the value deadband by entering an integer or real number in the Deadband box based upon the selected tag type.

   The value deadband sets an absolute threshold level in engineering units.

6. Set the log deadband by entering an integer or real number in the Log Deadband box based upon the selected tag type.

   Like the value deadband, the log deadband sets an absolute threshold in engineering units.

7. Select Save to save your deadband changes.

8. Select Close to close the Tagname Dictionary dialog box.