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For some reason whenever I play with a multimeter it always gives me results I never expect. In this case I am attempting to measure the current of a AA battery. I have the multimeter set to 10A on the dial and connecting red to the negative end of the battery and black to the positive end, giving me a reading of about +6.8. However if I switch the dial to 200mA with the same connections the reading goes off the scale but with a negative number, -1. Is this behavior normal? It is a digital Southwire 10030S multimeter.

After testing with an analog meter putting negative to negative and vise versa I get a positive reading of about 5 amps though the gauge gets stuck usually. It says PRIME Cleveland Ohio on the back.


Looks like I had the fuses in the back swapped with each other and after correcting it is now matching the readings of the analog meter :D

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  • \$\begingroup\$ Is it a digital or analog multimeter? \$\endgroup\$ – uint128_t Apr 19 '16 at 4:04
  • \$\begingroup\$ Digital, Southwire 10030S \$\endgroup\$ – Chicken Wing Apr 19 '16 at 4:06
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    \$\begingroup\$ It might be that the "-1" you are seeing is an overrange indication. Also, if your battery can push 6.8A, it's quite possible you have damaged your meter by running 6.8A through the 200mA range. \$\endgroup\$ – uint128_t Apr 19 '16 at 4:35
  • \$\begingroup\$ @uint128_t It was the fuses, but all's good now, reading about 4 amps. Is that normal for a AA battery? \$\endgroup\$ – Chicken Wing Apr 19 '16 at 4:37
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    \$\begingroup\$ @ChickenWing I'll assume that Alkaline is the chemistry of your battery (you didn't mention what the chemistry of the battery is). An AA battery can put out amperes of current. 4A, which you see, doesn't seem out of the ordinary. \$\endgroup\$ – Nick Alexeev Apr 19 '16 at 4:53
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If you have your probes plugged into the 10A jack (and ground), then you can actually measure the dead-short capacity of your battery (several amps depending on the age, chemistry, and depletion of the cell). USE CAUTION

If you have your probes plugged into the 10A jack and ground, then it is NOT VALID to try to read anything on the 200mA scale. A reading of "-1" is typically the indication of "OVERLOAD". NOT RECOMMENDED

If you have your probes plugged in to the mA jack and ground, then your AA cell will likely blow the fuse unless the cell is nearly dead. NOT RECOMMENDED.

Measuring the dead-short current capacity of your AA cell will kill it very quickly. It will also quite possibly cause extreme heating and is dangerous to your meter, and could even be hot enough to start a fire. NOT RECOMMENDED

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    \$\begingroup\$ It looks like I did blow a fuse after testing the continuity of the 200mA fuse. It's coated in white so there's really no visual representation. Lesson learned. The heat was also very noticeable which made me wonder if they can actually explode? I remember an old handheld I played with when I was a kid and the batteries had basically foamed in the back. \$\endgroup\$ – Chicken Wing Apr 19 '16 at 8:05
  • \$\begingroup\$ Nevermind. It actually says it can explode or leak on the casing xD \$\endgroup\$ – Chicken Wing Apr 19 '16 at 8:40
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An ideal amp meter has no resistance. You have essentially shorted out your battery by connecting an amp meter across the battery's terminal. This can lead to very dangerous situations.

An amp meter is used between a load (like a light bulb) and a power source (like a battery) to measure the current.

Care should be taken never to exceed the amp meter's upper limit. It is common for an amp meter to have fuses for the lower amp meter ranges.

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  • \$\begingroup\$ I was using a wire earlier to short it out and only thing that happened was some heat generated. I'll look into some of the safety protocols, etc, as I start playing with potentially more dangerous things. \$\endgroup\$ – Chicken Wing Apr 19 '16 at 5:02
  • \$\begingroup\$ @ChickenWing you do understand that shorting out a battery is generally a bad thing to do, right? There are types of batteries that will violently explode if you short their terminals together. \$\endgroup\$ – Dan Laks Apr 19 '16 at 6:07
  • \$\begingroup\$ Well, with an alkaline battery, very dangerous situations might be a bit of an exaggeration. They can heat small wires red hot. But apart from that there is not too much hazard, I don't think. \$\endgroup\$ – mkeith Apr 19 '16 at 6:08
  • \$\begingroup\$ @mkeith right, but I wouldn't expect someone who asked the question the OP asked to know enough to differentiate between non-dangerous batteries and dangerous ones. \$\endgroup\$ – Dan Laks Apr 19 '16 at 6:22
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    \$\begingroup\$ @DanLaks I wouldn't expect batteries from the back of a tv remote to be dangerous but what do I know. \$\endgroup\$ – Chicken Wing Apr 19 '16 at 7:30
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Well you have your probe stuck in the wrong hole for the switch setting... so I don't think you should expect anything sensible. On the other hand if you do put it in the right hole, you'll probably blow the fuse in the DMM (or damage it).

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    \$\begingroup\$ Might as well blow a few fuses for science. \$\endgroup\$ – Chicken Wing Apr 19 '16 at 5:03

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