I recently measured a brand new Duracell AA battery which is labeled as 1.5 V. The reading was 2.3 V. Is this ever normal for a fully charged battery, or is my multimeter broken?
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4\$\begingroup\$ no, a fully charged AA should be about 1.6. maybe if the cell was over-heated it could produce 2.3 but the smart bet is on a wanky meter. \$\endgroup\$– dandavisCommented Jun 6, 2017 at 9:02
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1\$\begingroup\$ Now you know you need a better multi-meter if you want measurements you can trust. Yours seems to be defective by design. \$\endgroup\$– Dmitry GrigoryevCommented Jun 6, 2017 at 10:08
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\$\begingroup\$ What kind of battery is it? Alkaline? "Alkaline batteries account for 80% of manufactured batteries in the US" \$\endgroup\$– Peter MortensenCommented Jun 7, 2017 at 8:55
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1\$\begingroup\$ Yes, it's alkaline. \$\endgroup\$– merlin2011Commented Jun 7, 2017 at 9:01
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1\$\begingroup\$ There are a few inexpensive DVMs that give high voltage readings when measuring DC voltage with the meter set to measure AC. \$\endgroup\$– Peter BennettCommented Mar 12, 2018 at 6:21
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1 Answer
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Most likely cause is that you need to replace the battery in your multimeter.
When the battery is very weak, the voltage drops to the point where the internal reference can no longer maintain regulation and it, in turn, also drops. A low reference voltage results in a high reading, which is exactly what you are seeing.
Usually there will be a low battery indicator in the display, but you may have not noticed. Personally, I think the display should be blanked rather than display an erroneous reading, but many meters do not do that.
answered Jun 6, 2017 at 9:15
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21\$\begingroup\$ I audited my half-a-dozen meters for low battery, when the warning comes on, when the reading goes bad, when the display blanks, and was horrified. If you have more than one meter, and a variable power supply, it's an exercise worth doing. The cheapo ones are not necessarily the worst! \$\endgroup\$– Neil_UKCommented Jun 6, 2017 at 9:20
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5\$\begingroup\$ I have an analog scope that I was using to measure resistance but got different readings for the same resistor at different multiplier settings. Changing the battery also fixed that. \$\endgroup\$– MichaelKCommented Jun 6, 2017 at 12:11
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46\$\begingroup\$ @Neil_UK It's like a twist on the clock saying: "A man with one multimeter knows what the voltage is, but a man with many multimeters is never quite sure" \$\endgroup\$– W5VOCommented Jun 6, 2017 at 13:26
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4\$\begingroup\$ @W5VO I thought that was about compasses. \$\endgroup\$– userCommented Jun 6, 2017 at 14:27
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4\$\begingroup\$ @MichaelKjörling, It is about measurement. Period. (but clocks are certainly oft mentioned.) \$\endgroup\$– hildredCommented Jun 6, 2017 at 15:47