Manually correct drift from pulse and CT

I’ve calibrated the CT to the pulse reading as best as I can, although the CT under reads at low power and over reads at higher loads but it’s not perfectly balanced, can I add a manual offset to the kWh feed? I can then add an offset every once in a while to keep the CT reading in line with the pulse count.
I tried using the offsetfeed in post process but this runs once and does not update?

Welcome, Barry, to the OEM forum.

That’s indeed a problem, it’s been on my radar for some time, and it’s because the c.t. errors change according to the load. And the v.t. (aka a.c. adapter) error also changes according to the mains voltage, just to complicate matters. So as you’ve found, it can be correct a low loads, or correct at high loads, but never both at the same time. I know what to do to correct it, whether it can be done with what little bit of memory that remains available is doubtful.

I’m not an emonCMS expert, so I can’t advise you whether it’s possible make a time-based adjustment in there. I think you could make a power-based adjustment using the input processes, multiply the power by (say) 1.001 if the power is less than (or greater than) some value, but I’ve never looked hard at those processes, so it would take some experimentation to work out what to do - and then more to get the numbers right.
I’m thinking in terms of if >, skip next where next would be x [times - calibration] and you’d have to work out the values to use. You wouldn’t be limited to one stage of correction, but getting several stages to work together would be tricky.

If that can’t be made to work, all I can suggest is you tweak the calibration so that it averages out over time.

I did think this, I could get it to work with just one adjustment unsure if this will work
Essentially a simple adjustment on very low loads (I have a powervault battery and it’s when that kicks in that the readings drift)

Also thanks, I think the box is great and quite a nice little commnity here.