I was recently doing some voltage measurements in the 5-20 mV range and the results seemed a bit off. Just for a reality check, I hooked up a ratio transformer and several different meters, checking from 10 VAC on down. These were an HP 400E, an HP3478 and my ancient HP 3455. All the meters were hooked up in parallel and the signal was 1 kHz. The 400E seemed way off on the lower ranges. The other two were pretty good. When I unhooked the other meters from the 400E, it was dead on, better than the other two. I assume the DVMs put some sort of HF pulses on the line that the fairly high bandwidth 400E can see. Anybody else ever get tripped up by this sort of thing?