The accuracy of a Zener is not good enough for your application. What
you need is a very low noise, high stability, low source resistance
precision power supply to replace the 1.5 V Battery. I would use a 1.5
V battery, and change it once every year.


Jerry G.



On Nov 29, 11:12*am, Bryce wrote:
My v7a vtvm (built by a guy who looks like me but a lot younger)
uses a 1.5v battery for resistance measurements. *I'm tempted
to replace it with a zener reference. *Looks easy: the battery
is grounded on neg side, so is one side of the 6.3vac.

I guess we didn't have zeners fifty years ago. *Dunno why Heath
didn't use several 1n34's in series (I think we DID have those!)
- thermal stability I suppose.

Is there some reason that a zener powered from rectified filament
voltage won't work here?