The curve shown looks like the warm up drift. some 25 ppm of change during warm up is not good, but also not that bad (e.g. 1.5 ppm/K and 16 K temperature rise). This number will likely scatter between units some are better and some may be worse. So the comparison with just 1 sample each gives not that much information.
It is still true, that from the construction the SDM3065 (and similar meters with a ADC chip and LM399 ref.) are a bit more prone to drift. The more problematic part of this is not the warm up part, but the long term (e.g. years) drift from aging.
As long that the others say and show that their 3065X meters does not show this behavior it seem to be an issue don't you think? I don't see that as a normal behavior for a 6.5 digit DMM.
L.E. Especially that it was calibrated and adjusted by Siglent. They should see that and fix it or at least tell me about. But they tell me "We have repaired your meter".
I remember your argument now. I like Siglent gear, but if you weren't too lazy to look, you'd see I also point out when Siglent has a problem with something. The difference is, I make sure they fix it properly,
and I make sure there's actually a problem with the device, and
not the operator first. 😉
Anyway, we did already discuss this. You complained that you didn't want to let the meter properly warm up, and that's ridiculous. You can't make claims about a device's drift without first following the warmup time specified. Which is a minimum of an hour! And if you look at your chart, it stabilizes after an hour. Somebody else said it needs 4 hours before it's truly stable, but I've found an hour is fine with mine. You ignore this and complain anyway.
If you don't follow the guidelines on the datasheet, don't complain about the specs on the datasheet either.
It's great that your meters that cost twice as much or more than your Siglent don't need much warmup time at all. That's awesome. If I could afford one, I would get the next generation of whatever Keithley releases. You can't take the datasheet from one device from one brand, and say another device from another brand sucks because it doesn't meet those specs. 🙄
In my attached tests, I did a proper warmup first. I would love to see you do a warmup first and then test your meter, and I've requested this before, but you didn't care. That's fine, you don't have to...but then the problem isn't proven to be with
your device.
As pointed out by Doug, who sells the VREF10-001, my 3065 was good enough to show the drift of the reference itself accurately.