I've had the Fluke 8505A burning in all day after resetting the zero reference on each DCV range and I have some results and they are impressive.
I use both my AD584-M references as well as had a Fluke 8800A connected just a control and a reference. Here are the results:
AD584-M Ref 1 Fluke 8505A Fluke 8800A
(Stated voltage)
2.50066V 2.50068V 2.5006V
4.99794V 4.99796V 4.9979V
7.50011V 7.50007V 7.5001V
9.99691V 9.99689V 9.9968V
AD584-M Ref 2 Fluke 8505A Fluke 8800A
(Stated voltage)
2.49937V 2.49939V 2.4994V
5.00030V 5.00031V 5.0003V
7.50042V 7.50039V 7.5004V
10.00096V 10.00093V 10.0009V
Ambient temp is 75 F with a R/H of 33%. This 8505A hasn't been calibrated since 2003 and clearly it is fine as is. But what I don't understand is why the zero references were off.
I suspect that the Ohms function zero ref is probably off too but I haven't checked that yet. That's tomorrow's project. And this puts the last nail in the coffin that the Siglent SDM 3055 is clearly not properly calibrated. It will read consistently low as I have demonstrated in the past but the nay-sayers insist I'm wrong. And I guess Siglent is not going to release a method for cal tweak as originally promised so I may have to send it to a cal lab at my expense.
Here's 7 digits of goodness. Will I ever actually upgrade to 7.5 digits? Never say never I guess.