Configure tags for historical logging

You select tags for historical logging from the Tagname Dictionary. When a selected tag’s value changes, the Historical Logger determines if an entry should be written to the log based upon each tag’s logging deadband and its current value.

If you change a tag from logged to not logged, the data associated with the tag is no longer saved to the log file. Logging resumes when logging is re-enabled. However, the historical trend shows a gap during the period when logging was disabled.

Changes to tag logging are ignored while WindowViewer is running the application. Logging changes to tags do not become effective until the running application is stopped and restarted.

You configure logging for each individual tag from the Tagname Dictionary.

Enable historical logging for tags

1. If needed, stop WindowViewer from running the application.

2. Open the application with WindowMaker.

3. Open the Tagname Dictionary.

4. Select a tag from the Tagname Dictionary list whose data you want to log.

5. Select the Log Data checkbox.

   

   The Tagname Dictionary dialog box includes other tag attributes closely associated with logging:

   • Log Deadband sets a engineering units threshold that must be exceeded before a tag’s value is written to the log file. Only new values outside of the deadband are written to the log file. Small value changes within the deadband range are ignored.

   • The Min EU and Max EU properties scale clamped raw values within a range of engineering units. Minimum and maximum EU properties set the upper and lower boundaries of the scaled values.

     The Min/Max engineering units determine the range boundary for log values shown in a trend. By default, an InTouch historical trend shows log data from 0-100 percent of the EU range.

6. Select Save.

7. Repeat these steps to enable logging for each tag whose data you want to log.

8. Select Close to close the Tagname Dictionary when you are done.