OPC DA Collector - Data Transform - NoOutput


I have an instrument that sends negative values when not in function (ex: -9999). I want to filter these values. The following OPC DA Data Transformation works fine: (x<0?(0):x) but instead of sending 0, I'd like to send nothing (NoOutput).

I do not see how to do that but the documentation seems to indicate that this is possible


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  • Hi eric. tremblay ,

    The only time we do not send a value is if deadbanding is being used, but that would not help in this scenario as the value would exceed that deadband limit.

    The calc server has this capability if you wanted to create a calc to filter out the negative values.

  • Thanks Steve,

    I knew the Calc Server can do that but I have many, many tags like this. That would almost double the number of tags. 

    What about the OPC UA collector? I saw that it can transform values as well as Qualities? I am planining to replace my OPC DA collectors by OPC UA collectors.


    Thanks again

    • eric. tremblay 

      We can't prevent the value from being sent but we can override the quality so that the value could be marked with a 'NoData' quality. This would at least prevent the value from being used in calculations or aggregation and also from being drawn on a trend.


  • Exactly what I need !

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