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I would like to know if the different internal resistances of different battery chemistry somehow affects the calibration of a digital multi-meter. If so, then what would the optimal battery chemistry be for commercially available multimeters.

For instance, would low self-discharge Alkaline batteries contribute to a more accurate reading than rechargeable Nickel-Cadmium batteries? Or vice-versa? Since Capacitors have ESR, I'm assuming so do batteries. Do certain battery types give a better ERS rating? Does this even matter for digital multimeters?

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  • \$\begingroup\$ What makes you think it does? They work with usually a wide range of voltages (most commonly 1.1-1.8V for AA/AAA alkaline/zinc) and already have to compensate for that, what change beyond that could a different chemistry possibly have? \$\endgroup\$ – PlasmaHH Jul 9 '18 at 13:12
  • \$\begingroup\$ I've expanded on my initial question with a couple of examples. Hope this will let people get a better feel of why I am asking this question. \$\endgroup\$ – Daniel Elefteriadis Jul 9 '18 at 13:13
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    \$\begingroup\$ You must think of an entirely different kind of multimeter if you draw so much amps that ESR matters. \$\endgroup\$ – PlasmaHH Jul 9 '18 at 13:14
  • \$\begingroup\$ Lithium cells are what I use for long life, high capacity, low ESR and lowest voltage drift. (Max-min)/avg \$\endgroup\$ – Tony Stewart Sunnyskyguy EE75 Jul 9 '18 at 13:31
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Multimeters use complex integrated circuits that are designed to work with a range of supply voltages, because they mean to be portable and therefore use batteries, and all batteries tend to drop their voltages as they worn out and age.

To accommodate this variable range, the DMM ICs have built-in voltage regulator(s) for important internal circuitry, and use internal self-calibrating techniques to keep their specified accuracy of measurements. And DMMs don't consume any heavy bursts of current when taking measurements (they use steady, continuously running integrators, not some fast high-consuming sampling ADC), so the ESRs of batteries (in fear of voltage sagging) don't make any difference as long as overall battery voltage stays above certain level. (I guess this was the false assumption that led to this inquiry).

Therefore, DMMs are effectively "de-coupled" from power supply, and therefore can use ANY kind of batteries, high-ESR, low-ESR, whatever (as long as their voltage is above certain level) without affecting their functionality. Of course, batteries with low self-discharge would be the best.

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What is the recommended battery chemistry for digital multimeters?

If you have a reputable meter the device's data sheet or manual will tell you what battery chemistry to use and specifically what battery they recommend.

I would like to know if the different internal resistances of different battery chemistry somehow affects the calibration of a digital multi-meter.

Low power hand-held meters consume very little power at all so this means they consume just a few tens to hundreds of microamps (when on) and this will not cause a significant volt drop across the battery internal resistance so it won't affect calibration. In addition, it is likely that meters use precision references to generate reference voltages and these chips will still be operating fine when the battery voltage has dropped to a level such that the LCD display is beginning to look a little low contrast.

If you need more clarification then you should post a specific circuit from a reputable supplier so that it can be analysed.

Footnote - my old Tandy DVM was bought in the early 90s and is still going strong on the original battery. I expect I'll need to replace it in the next ten years or so.

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Does this even matter for digital multimeters?

In a properly designed multimeter: NO.

A multimeter does not rely on the voltage of the batteries as a reference. If it would then 1% accuracy multimeters would be impossible to make.

The batteries have to supply a DC voltage in the range that the meter can use and be able to supply the required current.

Most meters have very low power requirements so they do not load the batteries that much. If the meter has a display backlight, that might consume most of the power.

If a meter gives a different reading of the same voltage with different batteries but the low battery indicator is not shown then you that is a poorly designed meter. When it does not complain about the batteries, the reading must be constant and accurate (assuming it is properly calibrated).

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Assuming 9V battery, you won't get much more life out of alkaline than so-called "Heavy duty" Zinc-Carbon cells (because the current draw is light).

I use Panasonic brand Zinc-Carbon cells from the dollar store, unless there's a case lot of 9V industrial alkaline cells in the store room.

Spot retail prices for the 9V Duracell batteries (eg. drugstores) can be on the extortionate side.

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