How to implement metadata?
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!
