Calculating power use

[Rowen]

Hi! I have amps and volts (3 phase) that I'm reading. I want to calculate kWh. I assume the easiest method would be to setup a meta data point but I'm a novice. any thoughts? I will also want to move this data to a chart and gauge.

Cheers,

Rick

[CraigWeb]

Hi Rowen

Kind of hard to see what your actual question is. Yes, a meta point will be the best option to calculate the power consumption, The meta-point can then be used in a dashboard with a <ma-get-point-value> component. Go through these documents and if you get stuck let us know what you have done so far and where exactly you are getting stuck,
https://help.infiniteautomation.com/meta-data-source

[phildunlap]

Hi Rowen,

I assume the amperage and voltage measurements are on the same device that you're polling? I would simply add both points into the context of the meta point, have only one of them update the context, and have a 1 second execution delay on the meta point (provided you are sampling less than once per few seconds, otherwise I would have a RuntimeManager.sleep(100); as the first thing (not for history generation though!)).

It should also be said that if you require a high degree of precision you should use an energy meter instead of extrapolating from sampled data.

[Pikey4]

Hi Rowen,
Hope this helps to get started.

I am only monitoring current on one of the 3 phases on a small job, and I've used:

return (1.732 * 0.7 * p217.value * p218.value)/1000;

1.732 = Square Root of 3
0.7 = power factor I measured onsite once
p217 = Amps
p218 = Voltage

It's not going to be as good as a power meter, but gets me trending which is all I am after and it's fairly close.

[Rowen]

@pikey4 Hey! Sorry I didn't reply sooner but your info helped me out. Thx.

R