How do I interpret the Audit Value using a GSV?

[Chris3EC]

I'm looking for a way to use the Audit Value for the controller to detect changes made programmatically. This link lays it out pretty cleary (page 47): https://literature.rockwellautomation.com/idc/groups/literature/documents/pm/1756-pm015_-en-p.pdf, but I'm not understanding how to relate the value that I get from the GSV to the bit number descriptions in the link above. Can anyone point me in the right direction?

 

[plvlce]

Change the style you are looking at your tag in to Binary, or just examine it at the bit level.

You might want to add bit level descriptions to the tag corresponding to the event descriptions.

 

[Chris3EC]

I think my mistake was assuming the Audit Value would change on a bit level that corresponds to the ChangesToDetect bit descriptions. It looks like the Audit Value just generates a new number randomly when a change is detected.

 

[plvlce]

I think my mistake was assuming the Audit Value would change on a bit level that corresponds to the ChangesToDetect bit descriptions. It looks like the Audit Value just generates a new number randomly when a change is detected.

That is what I had assumed as well, but it looks like you are correct that it just generates new numbers rather than actually making any indication of what was changed:

• A unique audit value is generated when a project is downloaded to the controller.
• When a change is detected in the controller, a new audit value is generated

All ChangesToDetect does is allow you to finetune what conditions will trigger the generation of a new Audit Value. Not nearly as useful as one might hope.

 

[Chris3EC]

Agreed. Thanks anyway!

 

[JeremyM]

It’s not random - it increments upon any change - so you could probably use current against previous value to set a flag of your own.

 

[Chris3EC]

It’s not random - it increments upon any change - so you could probably use current against previous value to set a flag of your own.

It does seem to increment, but I still don't see a way to use that value to determine exactly what type of change occurred. Indicating a change is easy enough, but I was hoping to track the type of changes made.

 

[JeremyM]

IIRC, you are correct. You can monitor a given set of type of change, but you can’t monitor multiple sets in parallel.