I got the emonPi the other day, with a pair of the 200A CTs. Setup was pretty straightforward, it seems to be monitoring my home power usage, making pretty charts and graphs, and all that good stuff.
However, voltage readings are way off. For a direct comparison, I just pulled the cover off the main panel and measured voltage there with my Fluke DMM–it measured 124.1V, compared to a reading on the emonPi of 112.1. That’s a difference of about 10%, which doubtless means all the power figures read 10% low as well.
I’ve followed the docs at Use In North America - Guide | OpenEnergyMonitor, and made this change:
…and I think this may be the problem. Nominal mains voltage in .us is 120/240, and has been for over 50 years. If the system is expecting 110 VAC to equate to 9 VAC out of the transformer (the “voltage sensor adapter” you sell, which I bought as part of this kit), and it’s actually 120 VAC-to-9 VAC, that would seem to explain what I’m seeing.
But regardless of the cause, how do I fix this?