Expanded Scale Voltmeter

[Pic_User]

Hi Alain,

I have a LM431A, in a solderless bread board, sitting on my workbench. I wanted to test the parameters at the span of interest. So far the stability of the 431 is impressive. It is configured as the standard shunt like the Zener in Figure B.
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Reading the specs on the device is one thing, but seeing it perform; priceless.

You are correct about both points, Zener temperature stability and battery voltage being dependant upon temperature. Hmmmm, I will have to check the coefficients of each to see if physically tying the Zener to the battery might compensate for each other. lol

Now, it would be simpler to tell us what's you've in mind ...

Mostly just thinking "out loud", and wanted to throw this in for discussion. Lead acid is a good place to start. Later, maybe measure for the “signature” of an end of charge for Nickel-Metal Hydride (NiMH) or similar cells.
I can’t help with the programming, so this is my way of helping the discussion that is so great on the forum.

Melanie said it in the other thread:

Trouble is I can guarantee your 5v reference probably isn't 5.0000v (and are you using 0.1% Resistors?) so we're splitting hairs about millivolt ADC tollerances anyway.

This sounds right to me, so it looks like we have to be careful not to overrun REAL world limitations chasing down the wrong path!

The software, averaging and/or weeding out aberrations is a great idea. I like the “bomb proofing“ technique brought up by Melanie.

Thoughts:
So, after we stabilize the Voltage device, do we want to probe (measure) the battery temperature? Put the temp into a program for correction?

Any other thoughts on the matter?

-Adam-