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Thread: Calceling value substitution for OPC variable

  1. #1
    Join Date
    24.09.2011
    Posts
    11

    Default Calceling value substitution for OPC variable

    Hello
    I would like to ask you how can I get back real value and status for OPC variable.
    I use standard "Variable diagnosis" picture for value and status change .
    There is no problem to make a value substitution. Only to get back last spontaneus value.

    Thanks a lot
    Jaro
    ZENON 6.51 OPC CLIENT V2.0

  2. #2

    Default Re: Calceling value substitution for OPC variable

    Hi Jaro,

    The OPC client driver is a spontaneous driver. When the driver adds an item from the OPC Server, the OPC server sends an initial value.

    Normally, the OPC server would only send a new value when the value, timestamp or status for this item changes. The driver in the will not request values cyclically by polling.

    So it seems that when you "substitute" a value (do you change to the alternate value?), the substitute value is used. But when you switch back to the spontaneous value, the value is not requested again from the OPC server. Is that what you are trying to say?

    When you reopen the variable diagnosis screen, does the variable get a correct value?

    Also, is the option to continuously update the values in the variable diagnosis screen set? Or did you try a manual update?

    When you set the option "DDE active" at the variable in the editor, compile runtime files and restart the runtime, does it make a difference?

    Best regards,
    Mark

  3. #3
    Join Date
    24.09.2011
    Posts
    11

    Default Re: Calceling value substitution for OPC variable

    Hi Mark
    You are right in most of the things. I used functions "Selected variable : switch to alternate value" and "Selected variable :switch to spontaneous value".
    I think that spontaneous data transsmition does not have to be the problem if driver notices also spontaneous data change in the background (like IEC60870 do). Otherwise driver has to do "General interrogation GI" or request value again. It is strange to interrogate 10 000 variables just because of one or few variables switched from alternate to spontaneous value.
    DDE active does not work. I tried manual and also continuous update in Variable diagnoses picture.
    How can I get actual or current value and state of variable after switching off alternate value?
    Thanks
    Jaro
    PS: The last value before switching to alternate value does not have to be the same like actual value.

  4. #4
    Join Date
    24.09.2011
    Posts
    11

    Default Re: Calceling value substitution for OPC variable

    I forgot. Functions: 'Selected variable turn on spontaneous value' and 'Selected variable turn off spontaneous value' do not work for OPC signals like I need.

  5. #5

    Default Re: Calceling value substitution for OPC variable

    Hi Jaro,

    I checked in the latest version, not in 6.51, and could reproduce an issue with the OPC client driver. I will forward this accordingly. If you would like this issue tracked and get a reference number, please contact your local COPA-DATA support.

    Best regards,
    Mark

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