4.8        Tag Fields

Tag Fields describe the attributes of each tag, for example Tag Name, Description, High Span, Low Span, Engineering Units, Alarm Limits, Alarm state and many more.  Tag Fields are available for all tags and all parameters of blocks.


Some Tag Fields represent values set during tag configuration and allow on-line changes (i.e. changing Alarm Limits on-line from VIEW without using

the Project Manager). These Tag fields require an Administrators Access Level (level 127) in order to change them.


Some Tag Fields are set by the WebAccess SCADA node software (for example, the Alarm Status). Users or administrators cannot change these read-only tag fields. The read/write character is described for each tag fields.


In addition to reading and writing the values of tags in the WebAccess, you can also access the Tag Fields in the Point Info Dialog Box or Graphic Displays.  Enter the Tag name followed by a periods (.) then the Tag Field.  For example TI001.TYPE will give the point type, TI001.ENUNITwill give the engineering units.


By modifying Tag Fields users, keymacros and scripts can enable and disable Alarming, modify Alarm Limits and other attributes of a Tag on-line in run-time mode. Normally, these changes are lost if the SCADA Node is restarted or downloaded. If On Line changes to Tag fields is enabled in SCADA Node Properties, on-line changes to these fields are saved to the Configuration Database on the Project Node (bwCfg.mdb).


These changes can be made during runtime using the Point Detail Displays. Or the change can be made using the Point Info Dialog box by appending the Tag Field to the tag name.


Tag Fields are most commonly used to enhance a Graphic or monitor a Tag’s Status in a Script. The most common change to a Tag Field is to Alarm Limits. Tag Fields also enable a certain Online Configuration Changes to Alarms, Description, Engineering Units and Change Limits.


Some tag fields are common to all point types, while others are available only to digital or analog points.