My pinpoint is obviously affected by electrical items plugged in nearby. I have the AC adapter on mine (got sick of buying 9v batteries and getting messed up readings).
Every time I plug or unplug something, the meter will spaz out a bit and takes a minute or two to get back to equilibrium...I've never noticed it when the lights come on, but I haven't been looking for it...my guess is that it happens then too.
No doubt some of the electrical gurus here can provide a technical explanation, but I assume it has something to do with micro surges in the circuit.
