On Sat, 29 Nov 2008 11:12:45 -0500, 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?


There is an absoute reason for never ever using ziner references in ohms
measurement.

The voltage must be stable and totally free of ripple or other electronic
noise. There s no ziner driven source that can do this cheaply.

Jist install a quality battery they last the normal shelf life of the battery
and are cheap. Nix on using ziners.

Gnack