Well,
in the past there was only one reasonable 10V voltage reference from Joe Geller, the SVR-T.
It was very stable over time, temperature and humidity and could be used as a starting reference point when you also had a transfer standard available.
It was stable to about 5ppm in all parameters, because it used a hermetic, ceramic package, based on the AD587UQ or LQ, if I remember correctly, and it was calibrated against a 3458A.
In this sense, it could really be used for metrology / calibration purposes. But these hermetic ICs are obsolete, as well as Joe Geller does not offer these references any more.
I attach a picture of a re-build, w/o the T.C. compensation by Lars Walenius.
All other such references are simply toys, I guess, and some are even hoaxes, so please pay attention.
Maybe the CheckDMM can be regarded as a reasonably stable reference, but he himself declares it as a (sanity) checker only, not as device for calibrating anything.?
It covers a few modes / ranges only, so it's not very handy, I think. Another problem for you is, that a resistive 10:1 divider wouldn't help you, as your DMMs probably have 10MOhm input resistance only, spoiling the divider ratio.
In general, calibrating any DMM requires to compare all ranges and all modes to a known good and stable reference standard, anything else is useless.
If you want to fully check or even adjust your DMM at home, I fear that you'll directly fall for volt-nuts passion.
There are very good DIY 10V references out there, on eevblog, based on either the much more stable LM399, or even based on the LTZ1000, all have to be calibrated against a good other reference.
As said, you would also need transfer standards for 1V, 100mV and 100 / 1000V to make a proper calibration of DCV alone.
Frank??
