### Calibration and 3-phase calculations in emoncms?

I have read some topics about calibration, and understand that the sketch needs to be altered in order to measure 3-phase systems.

One thing i do not understand is the following.

If i want to calibrate the voltage, cant i simply measure the voltage in my socket with at multimeter and add the appropriate multiple to calibrate in the emoncms when creating a feed?

If i want to calibrate CT. Cant i simply strap all three of them to a powerline, and add a known load (1kW for example) and just tune the values of the CTs in the emoncms? They should read 1000/voltage=current right? An they should all read the same number.

And if i want to calculate 3-phase power, cant i simply just add all three CTs into one feed, and multiply it by 1/3, and then multiply that with square root of 3, and multiply that with the feed for voltage that i allready calibrated.

(U1+U2+U3)/3  X  √3  X  I  = P

I understand that i cannot measure all the aspects of the 3phase power system with active / reactive power, phase angles or anything like that.

I understand that maybe this will not be the most correct way to measure, but since i dont understand why my method cannot be used i would be happy if someone can explain it to me.

Thanks for shining some light on this.

### Re: Calibration and 3-phase calculations in emoncms?

I ignore power when calibrating voltage and current separately, only looking at power and VA (or power factor) when setting the phase correction.

If i want to calibrate the voltage, cant i simply measure the voltage in my socket with at multimeter and add the appropriate multiple to calibrate in the emoncms when creating a feed?

If i want to calibrate CT. Cant i simply strap all three of them to a powerline, and add a known load (1kW for example) and just tune the values of the CTs in the emoncms? They should read 1000/voltage=current right? An they should all read the same number.

That is how I do it, except I use the serial monitor direct from the emonTx, and if needs be I add the rms current to the output. But I don't quite see how averaging the 3 phase voltages will help you, as the emonTx can only measure 1. If you've calibrated the voltage and current separately, all you need to do with the 3-phase sketch is the phase/timing correction.

The problem with using the claimed value of a load is that this value might or might not be accurate.

If you've only got emonCMS as the diagnostic display, then it does become harder. You can adjust the voltage with a calibration in emonCMS, and the power with a power calibration. But I would measure voltage and current to get the standard that you calibrate to, not the claimed load power.