Good morning everyone,
I’m facing an issue with the power reading of my ct connected to the emontx3 and emonpi. I installed a deye inverter and 48v home battery which is AC coupled on the grid side with pre existing solaredge inverter. After switching on the inverter the readings of the clamps went all over the place, i did not change anything on my setup which was working fine.
I then disconnected the new inverter and battery and the clamps showed a normal reading again. So the inverter is introducing such an electric noise to interfere with the normal reading of the clamps? The temp sensors kept on working fine, I also checked with an amperometric clamp which showed normal readings.
Any thoughts?
Welcome back, Maurizio
This does indeed sound as if it is a real possibility. The best place to solve an interference problem to to remove the source of the interference, so initially I would suggest you explain the problem to your installer and supplier and ask them to check the shielding, filtering and grounding of your inverter and ask what solution they might be able to offer.
If they cannot or will not solve your problem, it will be necessary to look at what can be done with the emonTx V3, but I have to say this is the very first report I have seen of a problem with interference from an inverter, and we know there are many users with other makes of inverter who have not reported a problem.
1 Like
Hi thanks for your answer, the inverter is working fine, and my setup is quite unusual as this second inverter is just a “storage inverter” and Ac coupled. Both the emonpi and emontx3 i have have power supply with voltage sensor, and they look also screwed up. Might it be a voltage sensing trouble? As if the second inverter would raise the voltage in the home circuit? Just guessing here because I have no clue, and it would bother me to drop my monitoring after years of use
By this you mean it appear to function as you expect - but this was not my point. What I was trying to get across is yours is the only inverter that’s been suspected of causing problems for the emonTx. So in addition to doing what it’s supposed to be doing, it might also be putting out switching transients or a badly distorted waveform, and it’s these that are confusing the emonTx.
It could be noise on the voltage input, or the current input, or both. Raising the voltage on its own, provided it is “clean”, won’t cause “readings … all over the place”, it will only raise the voltage and (presumably) the power readings.
The obvious step forwards would be to look at the waveforms involved, you might be able to do this yourself if you can borrow an oscilloscope, or if you’re not comfortable with this, you might be able to enlist the help of a local college or electronics club. This would have to be done in your house where the inverter is, of course.
Thanks Robert, I will check for noise with the scope, I will check the wave form, but, in the end, could apply some kind of filter to the emontx/emonpi or software correction? I’m trying to take out the voltage sensing power supply, is there a way to calibrate the ct coils on the emonpi/emontx?
I would recommend you first try to find the route the noise takes to get inside the emonTx. Are the voltage readings correct or "all over the place”? If you use the c1 configuration command, are the current readings correct or "all over the place”?
What worries me about filters is they introduce a phase shift, so you need to make sure exactly the same phase shift is introduced in both current and voltage inputs, or the real power calculation will be wrong.
Again, it wiil be better to filter the output of your inverter than filter the inputs of your emonTx4, because you will also reduce the noise all your other appliances receive.
You can calibrate the current inputs of the emonPi & emonTx, the current transformers themselves cannot be calibrated by you the user.