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How to interprt the numerical negative digital state values from the PI archive

Question asked by cranford on May 21, 2015
Latest reply on May 22, 2015 by gachen


We have an application the recovers PI data from the PI archive using the PI API and these calls:

piar_timedvalues

piar_interpvalues

The program is old and cannot be modified due to the strict controls maintained by our plant computer management policies.  We need to understand how to convert the negative digital state values back in to the literal equivalent without using another PI API call. In other words can you please describe how to manually interpret the negative numbers from the PI archive?

We need more than just the definitions that state use the upper and lower 16 bits etc. we need an example to really understand what it is we need to do.

Thank you!

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