On Thursday, 21 September 2017 18:51:33 UTC+1, 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?

Once I have the 10V (that might need it's own drive resistor?) for the
-ve side of the meter I think I'd need a 20k resistor in series with
the meter to my 10-15V supply (a lead acid battery)?

R = V/I = 5 / 250 x 10^-6 = 20k ohms.

Or ... I could use a straight potential divider on the grounds that a
moving coil meter isn't going to be that accurate in the first place?

Maybe: -Ve, 10k, 5k, +Ve with 20k in series with the meter across the
5K?

Am I close please? ;-)

Cheers, T i m

How accurate do you want the readings? Add your errors together. MC meters are usually pretty good on accuracy.


NT