First, I just sent this and forgot the tag.  I am sorry.

I have a DC multimeter that was manufactured around 1972 or so
that was intended for use by electronic technicians who happen to
be blind so there is a FET-based chopper and Wheatstone bridge in
what normally would be the meter movement.  To get a reading, one
turns a wire-wound pot and listens to a steady tone on a loud
speaker.  When one reaches the correct reading, the bridge
balances and the tone fades out in to a null.  If you go past the
null, the tone fades back up.

	The meter probably still works but one of the batteries
it uses is a 1.3 volt mercury cell which is the size of a
Double-A battery.

	It got to where the 1.3-volt double-A sized cell was hard
to find so I found a N-sized cell.  These are the same diameter
as a double-A but only about half as long.  I made a dummy cell
out of hard copper tubing of the right diameter and stuck a
spring in the tubing to press against a piece of copper at each
end to take up the rest of the space and that worked.  One simply
replaced the N cell more often.

	The mercury cell is a voltage reference so the readings
are all wrong if one puts in a double-A so my question is whether
there are any more environmentally friendly 1.3-volt cells that
can replace the mercury cell.

	The holder is double-A sized but I think there may be
room in the case to install a different holder such as a coin
cell if the new reference cell is shaped differently.

	The other batteries are a normal D cell and a 9-volt
snap terminal battery and neither of those are special so I
should be able to revive it if I can get a 1.3-volt reference which
would replace the mercury cell.  The load is rather low as I
remember that it normally lasted quite a long time before needing
to be replaced.

	I keep intending to get it working again as it is a
pretty decent analog DC volt, ohm and amp meter and will read up
to ten amps on it's highest current range.

	It's been sitting on my work bench for several years,
mocking me to put it back in service again.

Thanks for any constructive suggestions.

Martin McCormick  WB5AGZ
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