Reversing CT inputs in software?

My electrician installed my two CTs and one of them is giving negative results. I understand this means they installed it the wrong way.

I hesitate to go in and try to fix it myself, so can it be resolved in software? I tried using the absolute process but it says it wants a real number. I’m not sure how to proceed.

Hi Jevin,

Welcome aboard!

To “fix it via software,” multiply the result by -1 in emonCMS.

To "do a hardware fix, "swap the leads to the CT that’s giving you the negative numbers.
(which may involve some minor “wire surgery.” Understandable if you choose to not go this route)

And you need to do that with the power off - so unless the leads are on screw connections, that could be impossible. Although it’s likely that the c.t. leads will be perfectly safe if you disconnect them, there’s no guarantee of that and they might develop a nasty if not dangerous voltage that might destroy the c.t.

I think that’s what I did here, is that right?

How do I correct the emonpi: power1pluspower2 feed?

Is it by creating “Virtual Feed” using the corrected power2 like this? If that’s the case, I can’t select that generated fee in that “My Electric” App

That looks good to me.

Basically - you can’t. The purpose of including power1pluspower2 in the transmitted data was to remove errors that result from the two separate values being received at slightly different times - the result of that was one could be used in one calculation and the other in the next, leading to discrepancies and inconsistency.

I don’t have a working emonPi, so I can’t experiment and help and more than that, I’m afraid.

If you’re willing to delve into the Arduino sketch serving the analogue “emon” part of the emonPi, then you could put the minus sign in there and have all three powers correct. That might be a “better” solution but one harder to implement - plus you’d have non-standard software which might haunt you at some point in the future.

Nuts. I did forget that important bit of info. :frowning_face:
And I know better, having read your advice (more than just a time or two)
about not trusting a CT’s internal voltage limiter.

1 Like