From Qld to Sydney and beyond to Royal National Park and the Illawarra. It was my first chance to do a proper roadtrip in the EV since the state borders opened up post COVID. With 350kW ultra-rapid chargers every 200km along the A1, charging was never an issue.
From memory those internal band gap references are very stable but not particularly accurate, so your solution sounds perfect. Do you just self-calibrate each time you boot?
That would be well suited to hooking up to a calibrator should you ever wish to do a spot-check on your accuracy.
If possible, it might be worth keeping the AC-DC supply sourced from its own terminal that you can just loop to one of the Line inputs at installation time. Have a look at the photo here and the description here, to see what I mean.
An earlier version of that meter had the power supply internally hardwired to L1 and that caused grief when trying to put L1 on the calibrator as the calibrator’s voltage signal (20 mA limited) got distorted when the SMPS did its thing. Breaking them out like that makes installation ever so slightly more complex (one more loop) but means in the lab you can power the SMPS directly from the mains and point the calibrator at the ZMPT101.