DC voltmeter gauges

50C8DAN50C8DAN Posts: 2,366Senior Contributor
I thought I would pass this along for what it is worth.  It is really hard to find a panel voltmeter gauge that is set for more than 6V as the minimum due to 12V being the most common today.  Back in the day, most vehicles used ammeters, not voltmeters and they are few and far between if can be found at all (I think the '39 - '41 Fords used 6V voltmeters but not sure).  So the other day I picked up a cool-looking 10V max panel voltmeter.  I got it home and looked at the face and in small lettering, it said A.C. Volts.  I thought darn I just wasted my money as it needs to be DC.  So what to do.  I then recalled my college electronic course and how voltmeters are wired.  DC is pretty simple just a wire coil and two leads, but with AC there is a diode rectifier so it is reading both the + and - swings in the voltage, and there is sometimes a capacitor to dampen any fluctuations.  So I got a battery and wire and bingo it read perfectly what the battery voltage was and if you flip it around it still reads correctly as the voltage will go on one side of the rectifier or the other and still read just volts!

That was back in the days before all the solid-state gauges.  These days the rectifier is often solid-state and most likely a new gauge will read nothing at all if you hook it up to a battery.  So if you want a voltmeter for your Hudson just find an older AC panel voltmeter and bingo you are set.
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