I have a oil pressure guage from a seaking helicopter, I'd like to make this work as a voltmeter for now.
It has 3 discs attached to the shaft for the pointer, one just has a magnet around it so I guess this is just for damping.
The other 2 discs have electromagnet coils around them with copper shunts.
I'm assuming that this guage works similar to a frequency meter, where the ac currents in the coils pull the pointer one way or the other depending which is greater.
So I was thinking of putting 400hz (standard aircraft power freq) ac through a resistor, maybe 10ma to one coil, and the same ac supply to the other coil through a pot, and see if varying the pot moves the pointer.
Anyone have any knowledge of this kind of guage, I've never seen inside one like this before.
A 555/4017 and some small trannys as a h bridge would make a little control circuit, or maybe a power op amp.