I cannot say I am disappointed but perhaps I was expecting a little better than this
What in particular could have been better? The peak to peak noise looks good to me.
I did some testing with a voltage reference (VRE102CA) that I've confirmed to have no popcorn noise and a much lower 0.1-10Hz noise than a typical LM399.
2 images attached.
5 NPLC, no filter, AZ offLooks good, there appears to be a hint of popcorn noise from the onboard LM399. (Edit: popcorn doesn't show up in further captures, probably just a random occurrence)
5 NPLC, no filter, AZ onWhile it's well within the expectations of a 6.5 digit meter, I would say there's a slight bug here as shown by the periodic waveform. Looking at the CSV sample data, it appears that the time for each sample is 2x 5 PLC + 2.09ms (202.09ms). I presume that 2.09ms is the total mux settling time for the AZ mode, but I'd say the duration should ideally be 2 PLC, 1 PLC before each phase. Just a guess though, the cause could be something else. Does the DMM6500 synchronize to actual AC frequency? (Edit: I would guess it might; time between samples in non-AZ mode corresponds to 50.016 Hz)
I did find a software bug where if you set up a waveform trigger, use it, then clear all the triggers, you still can't change the range to 'Auto' (gives an error about being in analog trigger mode, despite the triggerflow model being empty).