xpyttl napisa³(a):
Feed the two voltages into a microcontroller that does
the math and operates the display (digital of course). Analog isn't going
to be so popular because you not only need a meter (generally harder to get
and expensive these days), but you will need some custom meter face, and
what it needs to look like won't be all that obvious.

I was thinkink about it, but i want to do it "as much analogue as
possible" ;-)

Thank you for response

MAc
sp9mrn