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Negative value in DNPr not coming

Bhadresh

I am trying Schneider NOR module to read data over DNPr protocol. Has anyone have tried to read negative value from NOR in CitectSCADA ?

As i am not getting value in negative. Instead its displaying 65535 like that value. I tried to read same tag in Kepserver and datatype with Short datatype and its reading negative value properly. Even Kepware also not able to read same negative value using Long/read (Which only support for Analog Input in Citect).

Any idea about this or there is limitation of driver that we are not able to read INT datatype using DNPr protocol.

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  • Indeed, according to the DNPR driver documentation you can only use LONG (for 16/32 bit integer values) an REAL (for floating point values) when reading analog inputs. What is the exact problem with that?

    Your initial question was about not being able to read negative values. Did that issue occur only when you configured the tags as INT?
    If so, please use LONG instead. INTs can only hold 16 bits and the minus-sign is probably stored at bit 31, so that should explain the issue in your case.

    You may or may not have to configure scaling like Andrew mentioned earlier. Please try these options and let us know what you find.

    Best regards,
    Patrick
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  • Indeed, according to the DNPR driver documentation you can only use LONG (for 16/32 bit integer values) an REAL (for floating point values) when reading analog inputs. What is the exact problem with that?

    Your initial question was about not being able to read negative values. Did that issue occur only when you configured the tags as INT?
    If so, please use LONG instead. INTs can only hold 16 bits and the minus-sign is probably stored at bit 31, so that should explain the issue in your case.

    You may or may not have to configure scaling like Andrew mentioned earlier. Please try these options and let us know what you find.

    Best regards,
    Patrick
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