This code is for a dual voltmeter as described here: https://www.crystalfontz.com/blog/dual-voltmeter-for-rv-electrical-systems/
I have an RV that has both a vehicle electrical system and a camper electrical system. I wanted a way to see the voltages of both systems at a glance while driving.
I tried some cheesey voltmeters from e-bay and some other cheesey voltmeters from Amazon but I was not happy with the accuracy or stability. I was not able to find a meter that would work well in a vehicle, show two voltages, and have good accuracy.
Why go to the trouble of making my own meter?
1)Visibility: I assembled all the van electrics (solar, B2B charger, 400AH LiFePo battery bank, inverter, etc), and while they seem to work fine, it is comforting to be able to keep an eye on them.
2)Trust: I wanted a meter that would read really close to my Fluke DMM. This meter does. The various cheesey off-the-shelf meters I got from the usual suspects on eBay and Amazon did not even agree with each other, let alone a DMM.
3)History: I love to see the time history of what has been happening in the last few minutes.
4)Fun: It sounded like a fun project.