Default emonpi kit calibration?

Hardware emonPi
1

Hello, I bought an emonpi shield kit, 2 CTs sensors and a AC-AC sensor (eurooo-plug) a few months ago.
Now I have a digital counter from my power company so I can compare the emonpi value and the real value i’m charged for. (sort of because i can only see live apparent power consumption)

The value I got from emonpi is quite above the real value, especially at high load.
I guess it is a calibration issue.
I read the calibration page in the guide, but now my setup is installed, it is quite difficult to remove everything.

Is there some value I should change in the config files with the defaut CT and AC-AC adaptator that were delivered to me ?

here’s the comparison between the use feed and the value I get from my counter. Again, not srictly the same, the PAPP is the apparent power consomption (in VA units), but it shouldn’t be lower the emonpi (in W unit)

Thank you

image
image1114×566 55.6 KB

2

It’s going to be a very long process of trial and error to get the calibration anywhere near correct if you can’t run controlled tests.

What exactly is LINKY PAPP? - I take it, it is from your supplier’s meter?

What you need to do is first is adjust the calibration constant for voltage in the “emon” front end so that the correct voltage is reported. This is probably the main source of error as the EU a.c. adapter has a different calibration to the UK one. Then, using high power resistive loads, adjust the current calibration so that the current reported agrees with your supplier’s meter - if that gives you access to the current, else you must compute it from the voltage & power/energy. Finally, you’ll need to adjust the phase calibration so that real (active) power/energy agree.
If you have a sufficiently modern sketch in the “emon” front end, you can adjust the calibration via emonCMS. I’ve lost track of what is pre-loaded now by The Shop (because I’m working on one or two versions ahead :grinning: ).

3

Yes, the CT is always an estimation.

Personally I multiply the incoming CT Input so it matches (in my case) the pulse input. Scale factor is currently 0.9438 on my main supply. Last time I checked it was less than 1% difference IIRC.

It is simpler than Robert’s way :slight_smile:

[edit]
You can easily work out what the scal factor needs to be on that graph page. In the box below, simply add the scale factor until it fits.

4

Yes apparent power. Sadly, intensity, voltage and … active power are not available

I don’t think I can do that without intensity, voltage or active power values unless I unhook everything and put it on a bench

You mean by editing emonhub.conf via emoncms or are you refering to something else ?

Thank you

5

By comparing use_kwh and my actual metering i see a 0.92 factor.
By apply that to my graph, they almost align (on the high value).

So I guess I’ll do that.

Do you apply in emonhub.conf like that ?

[[5]]
nodename = emonpi
[[[rx]]]
names = power1,power2,power1pluspower2,vrms,t1,t2,t3,t4,t5,t6,pulsecount
datacodes = h, h, h, h, h, h, h, h, h, h, L
scales = 0.92,1,1,0.01,0.1,0.1,0.1,0.1,0.1,0.1,1
units = W,W,W,V,C,C,C,C,C,C,p

or through the input/feed configuration ?

Aymeric

6

You can do either, but I favour doing the correction as close to the source of the data as possible - in emonHub.
But there’s no guarantee that doing what you are proposing will give correct values at different loads, especially small loads that often have a very poor power factor.

I was referring to the Serial Monitor in Admin. (emonCMS).

7

No I do it on the input processing.