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  • I have a Data point from a MODBUS device that I read on a periodic basis.
    The raw data from the device must be run through a calculation in order to display in the graphical view widget.

    I was trying the Metadata data point and was not able to get it to work.
    my calculation is simple in javascript:
    var my = (p1-640)/16.0;
    return my;

    does not seem to work, meaning the graphical widget does not update.

    What am I missing, is there an example similar to this?


  • Hi tcontrada,

    i would have written that as

    return (p1.value - 640)/16.0;

    the "my" would probably be aliasing the variable name for the point to refer to itself, and one should call for the .value property of the context point.

    I do not know what you mean, "does not seem to work, meaning the graphical widget does not update." but I suspect the problem is the same. Check it on the data point details page if you are making a custom dashboard, just so one can more easily know where things are going wrong.


  • I see, working now....Thanks!


  • No problem! Just so you know, these calculations could probably be performed in the modbus point locator, which would probably be more efficient. It's value*multiplier + additive, so

    (value-640)/16 --> value*.0.0625 - 40 would be equivalent, so multiplier=0.0625 additive=-40 but there can be benefits to using a Meta point, if you're wanting to keep the raw values around too for some reason.


  • OK, cool, I will try that as well...Thanks!