Just received this device — https://dmmcheckplus.com/shop/ols/products/dmmcheck-plus-without-enclosure
So as I know it’s complicated to measure voltage and resistance at his level of precision. Because temperature and even moisture can affect it. So I can live with some delta from reference 🙂
Calibration certificate:
HP 34401a specs:
DCV (5.0000 ref) — 0.0008% (worst measurement was 0.0016% diff):
ACV (4.999 ref) around 1.5mV difference — biggest difference for all measurements — on photo — 0.025% difference — measuring AC not the best side of it 🙂 it was the best measurement, worst was at 100Hz — 0.062% difference:
DCI (1.0002 ref) — 0.05%:
ACI:
It’s not measuring such a small values of ACI, so skipping.
Freq. (10.000368 ref) — 0.0002%:
Also now we know that this china guy is not so bad too 🙂
Pseudo 4-wires for resistance:
100K (100.061 ref) — 0.006%:
10K (9.9998 ref) — 0.008%:
1K (0.9994 ref) — 0.007%:
100R (99.935 ref) — 0.0016%:
And of course it shows 5.0000v for 5 digit resolutions which is fully equals calibration value 🙂
My HP is pretty old (looks like from 1995 year) and I don’t know when it was recalibrated, so it’s it pretty good condition.