CT clip reading inaccurate

Tags: #<Tag:0x00007fdb68d95440>

Looking for advice on why my readings are incorrect. Today I finally got round to fitting my EmonPi and CT clips. (my old post about setting it up is here)

I have the YHDC SCT-013-000 connected to the cable coming into my house showing import export. This is all correct and on the front panel of the EmonPi I see the correct values. Inside the consumer unit I have the YHDC SCT006 connected to the solar generation cable. And this is where things start to get strange. The readings from my solar appear to be 2-3 times what I am seeing on my Inverter read out on my Solar.

Readings right now on EmonCMS are:

USE NOW - 3234W
SOLAR PV - 4467W

Exporting is correct, but solar PV and Use are incorrect. I am have solar of about 1800w according to inverter and using about 600w in the house judging by what is switched on.

I saw this post that states the result of using the YHDC SCT006 would be 2.5x the actual value.

So my question is where in the config settings to I tell it CT2 feed needs dividing by 2.5?

Any help greatly appreciated!

The emonPi is designed and calibrated for a 100 A : 50 mA c.t. Your SCT006 is 20 A : 25 mA

Therefore, your emonPi will indicate 100 A when you have 40 A flowing (if that were possible). That is where the “2.5” comes from.

The calibration to change is in emonhub.conf. (You can access and edit that in your web browser.) Find the section for Node 5 - the emonPi:

    nodename = emonpi
        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 = 1,1,1,0.01,0.1,0.1,0.1,0.1,0.1,0.1,1
        units = W,W,W,V,C,C,C,C,C,C,p

The “scales” values are the ones to adjust - they map 1:1 to the “names” above.
Change the second “1” to 0.4.
Note you must not use “power1pluspower2”, because that is the sum of power1 and power2 done in the analogue front end, a long time before “scales=” factor is applied, so the sum there can never be correct.

1 Like