Changing Scales on an Analog Meter

[wooferhound]

I have some 50ma VU meters from some old cassette players. I put a resister in series with one of them to make an indicator for my systems battery voltage. I only have 2 marks on it to indicate 12 & 14.4 volts. Here is a picture of it at the top of the image

as you can see my 2 marks are quite close together. I would like to get the meter to read 10 volts at the bottom of the scale and 15 volts at the top of the scale.

Does anybody know a way to wire it to get this scale?
I don't need exact resistor values, just a general Idea, I can tweak the values till I get it operating like I want it to. I will be building another meter to check the batteries for my wireless microphones and I will want a similar system to spread out the scale.

[TomW]

Those meters are NOT linear scale they are log scale or something like an audio taper potentiometer??

Anyway I doubt you will have much luck. I didn't find a way to get them to work much beyond one point on the meter that was accurate.

Good Luck

Tom

[wooferhound]

I don't care too much about linearity, as long as I can get the Low & High readings approximately right.

[Nil]

Hi Wofferhound,

The only thing I've seen that would help you is this post by Commanda http://www.fieldlines.com/board/index.php/topic,127492.html

Other than that I'm not sure. I hope someone has a simpler idea.

BTW has anyone seen Commanda around since the move?

[RP]

Commanda seems to have exactly what you're looking for but if you want to try something quick and dirty to get the 10 volt offset, I'd suggest adding a zener in series with your resistors.

[gizmo]

This is what you want. Its an article I put together about converting a old audio meter to a expanded scale volt meter.

http://www.thebackshed.com/Windmill/articles/ExpandedScaleVoltMeter.asp



Hope that helps.

Glenn

[kurt]

there is a program floating around on this board that will print you a nice new scale for your meter with your range marked on it but i forget who wrote it someone will remember.

[wooferhound]

It was BTHumble . . . I can't find the original story but here is the program . . .
http://www.otherpower.com/images/scimages/236/MeterDial.zip

Thanks for the replies
Gizmo you are the winner, I'm gonna try your circuit.

[ghurd]

I like Gizmo's simplest circuit.

If it acts goofy or causes something else to act goofy, hang a tiny cap (0.01uF is plenty) and huge value resistor (10M?) in parallel with the Zener.
(Zener, cap, and resistor, all 3 in parallel)
G-

[gizmo]

Thats a good tip Ghurd, I'll add that to the article if its OK with you. I have seen noisy zeners in the past.

Glenn

[ghurd]

Thats a good tip Ghurd, I'll add that to the article if its OK with you. I have seen noisy zeners in the past.

Glenn

It is fine with me.
Spell my name properly on the royalty check .  (Only 1 N)   

Might add "if it is still acting goofy, try a 0.1uF cap".

I doubt it will have much (any) effect with an analog meter circuit, though it would help people like me who try to hybrid such circuits.
G-

[gizmo]

Thanks Ghurd, I updated the page.

Glenn