On Thursday, September 21, 2017 at 10:51:33 AM UTC-7, T i m wrote:
Hi All,

Not a 'repair' question as such but I was thinking of using an old
skool 250uA FSD moving coil panel meter to read the 10 to 15V DC range
(a lead acid battery charge / discharge indicator), next to a 0-30A
Ammeter (inc shunt etc).

I was thinking of using either a voltage reference such as
LM4040DIZ-10.0 or could I get away with a simple zener (BZX55C?) with
associated resistor(s) please?

You can use any zener under 10V to do a 10V zero offset (just divide down the
input voltage until that 10V input matches the zener knee). So, with an
arbitrary zener (I'd use a TL431 as a 2.5V reference, they're convenient
and accurate) and a trimmer acting as voltage divider, it just remains
to make a range-setting resistor in series with the meter.

The important thing, is to doodle up a really nifty scale for your meter
that indicates 10V to 15V, with clear markings, along the pointer's arc,
maybe with a bunch of subdivision marks. Last time I did that, it took
a plotter and a bit of custom software to draw the arcs and labels,
then some fiddling with the faceplate of the meter to
affix it (warning: you need to worry about laser-print ink, paper, glue compatibility).