Quote:

It's my understanding that they don't sense voltage so much as they actually measure resistance. Don't forget, they are powered by a (more or less) constant 5 volts. The variable factor in their operation is the resistance to ground. Each gauge is calibrated to a specific range of resistance. Essentially, what they are is Ohmmeters.

So, I don't really think you could convert one to measure volts.



Incorrect..
The gauges are voltmeters, and by changing the resistance revises the amount of swing of the meter by decreasing the incoming voltage...

Just my $0.01..