Voltage differences

Hi all,
I’ve just installed an Emonpi and an Emontx. They are both located in my intake cupboard.
The Emonpi has 2xCT inputs and an AC-AC voltage sensor input. I’m running local Emoncms at the moment on it as well.
The Emontx has 3xCT and an AC-AC voltage sensor input.
The 2 AC-AC voltage sensors are plugged into the SAME double socket outlet and yet they are reporting voltages that can be over 5% different?
Does anybody else see this behaviour or have I got a faulty unit?
Thanks for your time.

There are things called manufacturing tolerances. The output of the a.c. adapter is specified as 11.6 V ±3% on no load, so that alone, ignoring the components inside the emonTx and emonPi, could account for the difference. This of course is why you can calibrate the devices, so that those tolerance variations can be corrected. The calibration procedure for the emonTx is spelled out in the ‘Learn’ section, and/or you can calibrate the emonPi by adjusting the “scales = …” values in emonhub.conf. I’ve repeated this many times here, so a search for that phrase should find many examples.