Batteries for voltage reference

I remember tales from many many years ago about using fresh batteries as a simple, cheap, and readily available voltage reference.

Has anybody tested that recently?

Assume I'm using standard AA alkaline batteries. How much do they vary over temperature, age, and from brand to brand? How much do they vary over manufacturing time within the same brand?

That might be a fun science project.

Are there other inexpensive references that are easily available?

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Reply to
Hal Murray
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Search for voltage reference on Digikey or Mouser or other.

I bet some are so stable your measuring equipment won't be sensitive enough to measure a change.

D from BC

Reply to
D from BC

There has been extensive discussion on this in the past, Google will show you. But this idea is just so antiquated now it's not even worth considering.

Yes, bandgap voltage reference IC's are available that do just this. They can cost anywhere from a few 10's of cents to a few 10's of dollars depending on the specs.

Digikey have thousands of items listed:

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0.1% ones cost only a few dollars for example.

Dave.

Reply to
David L. Jones

If you use a battery technology that doesn't include a gaseous byproduct, it works OK. Mercury batteries (and best, the Weston style standard cells) are fine. They're also 'WAY more expensive than a good IC reference. TL431 (bandgap) or uA723 (zener) are low tempco and low drift references, under $1, and many trimmed IC with buffered references are available in the $3-and-up range.

Carbon-zinc and even Mn alkaline are NOT recommended; they have barometric sensitivity and can 'burp' a little gas past the seal and do a ramp/step kind of AC output when loaded.

Reply to
whit3rd

LED

Regards,

Boris Mohar

Got Knock? - see: Viatrack Printed Circuit Designs (among other things)

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void _-void-_ in the obvious place

Reply to
Boris Mohar

Batteries are a PITA. But, before cheap IC refs were readily available, there was a number of "Electronic" reference cells available, designed to replace Weston Cells and the like. Typically they used carefully selected Zener diodes of about 5.2 volts, somewhere about there Zeners/Avalanche diodes have a zero TC.

Cropico was one such manufacturer in the UK. I see they are still in business, but no longer seem to have references.

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Reply to
Barry Lennox

If you don't mind being years out of calibration (usually) and ROHS issues, old standard cells are not so hard to come by. The one I have is built into an old millivolt potentiometer instrument (there's some vintage electronics for you - standard cell and a really fiddly galvanometer). However, given the choice of buying such a thing or buying a modern solid state reference, buy the reference - it takes up less space, among other things. It may also be temperature-compensated, while I seem to recall that standard cells require a specific temperature to be correct.

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Reply to
Ecnerwal

Back in the dark ages when they sold VTVM kits, one of the manufacturers directed the builder to calibrate the meter by assuming the supplied D cell was 1.xx Volts.

Tam

Reply to
Tam/WB2TT

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The biggest problem with standard cells for lab use is their horrible temperature coefficient. Batteries are a great deal quieter than voltage references, which sometimes matters more than long term stability...but as someone else suggested, a LED can be useful when you need a quiet reference.

A red LED with its cathode grounded, running at constant current and buffered by an NPN emitter follower makes nice quiet 1V reference with lowish tempco, due to the TC of the LED and the Vbe more or less cancelling. Give it some reasonable current, and this can easily be 15 dB quieter than a bandgap. (Bandgaps use junction forward voltages too, but have to multiply up a smaller voltage, leading to more noise.)

Cheers,

Phil Hobbs

Reply to
Phil Hobbs

Thanks. That's probably what I'm remembering. Mine was an Eico. (I think.)

I measured all the never-used batteries I could find.

1.622 Mar 2014 Safeway AA 1.619 Mar 2124 Duracell AA 1.580 Mar 2007 Safeway AA 1.575 Mar 2008 Duracell AA 1.575 Jan 2002 Duracell D 1.436 Jan 2002 Duracell 9V (8.62/6)

The dates are the expiration date.

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Reply to
Hal Murray

snipped-for-privacy@ip-64-139-1-69.sjc.megapath.net (Hal Murray) wrote in news:CfOdnTosuu0_nNzanZ2dnUVZ snipped-for-privacy@megapath.net:

yes,and what sort of resolution could you get on the VTVM scale?

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Jim Yanik

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