Why does Analog Multimeter need AAA Batery

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I'll embarrass myself with this one, but so what...
Just got this little hobbyist's pocket analog multimeter, and it has a slot for 1 AAA battery, currently empty. The manual only mentions it and doesn't say why is the battery needed. When I connect the probes to test the power, the needle deflects, correctly indicating voltage/resistance, once again - without the battery present. So what is the battery for then?
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Subject: Why does Analog Multimeter need AAA Batery Newsgroup: alt.home.repair => Newbie <= wrote:>I'll embarrass myself with this one, but so what...

It would be needed to measure resistance. How on Earth are you measuring resistance without a voltage source? Tell the truth... Did you REALLY measure a resistor?
--

-Graham

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The battery is necessary when measuring resistance. If you put the meter on the resistance scale and touch the probe tips together, the meter should deflect to the zero ohms end if the battery is installed.
Newbie wrote:

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Hi Newbie, hope you are having a nice day
On 25-Feb-05 At About 13:38:17, Newbie wrote to All Subject: Why does Analog Multimeter need AAA Batery
N> I'll embarrass myself with this one, but so what...
N> Just got this little hobbyist's pocket analog multimeter, and it has N> a slot for 1 AAA battery, currently empty. The manual only mentions N> it and doesn't say why is the battery needed. When I connect the N> probes to test the power, the needle deflects, correctly indicating N> voltage/resistance, once again -without the battery present. N> So what is the battery for then?
It is needed for the resistance ( Ohm) readings.
-=> HvacTech2 <=-
.. **FLASH** Eveready Bunny arrested, charged with battery.
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The only test/s that a simple analog meter (with a needle or moving finger) should require a battery for is continuity/resistance tests. You are correct; an analog meter will measure external sources of electrical voltage and/or current without the battery. However when you desire to measure an inanimate or other wise unpowered circuit or item the source of electricity for that measurement is the small battery inside the meter. By the way don't try to measure any external voltage or current with the meter set to "Ohms" or "Resistance" ranges! For an example; holding a bulb/lamp in your hand you connect the test leads (set to ohms/continuity etc.) to a lamp/bulb in attempt to find out if it's 'blown' or OK? You will not get any reading at all unless that battery is in place! That makes sense of course because current will not flow without a source of voltage. BTW is this a troll? If not suggest that a quick self paced course on basic Ohm's Law will assist advantageous use of the meter and perhaps minimize the chances of "Blowing the sh**" out of it! Which we have all done at one time or another. Also read the little book that should come with the meter. There are some applications where such a small analog meter can do better job than a more sophisticated more sensitive one!
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It's needed to measure resistance (ohms).
--
Peace,
BobJ


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"It's an annoyance. Take the meter out of a drawer, and the battery's dead. You might add a diode and series 47K ohm resistor to the switch contact used to measure 120 VAC and leave the meter leads plugged into a wall socket to monitor house voltage and keep the battery charged. "
Another example of practical advice from pointed head academia.
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It's an annoyance. Take the meter out of a drawer, and the battery's dead. You might add a diode and series 47K ohm resistor to the switch contact used to measure 120 VAC and leave the meter leads plugged into a wall socket to monitor house voltage and keep the battery charged.
Nick
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Thanks Terry, and everyone else for your help. In retrospect it appears sooo obvious that resistance measurement requires some kind of power source...
Thanks again everyone....
| > I'll embarrass myself with this one, but so what... | > | > Just got this little hobbyist's pocket analog multimeter, and it has a | > slot | > for 1 AAA battery, currently empty. The manual only mentions it and | > doesn't | > say why is the battery needed. When I connect the probes to test the | > power, | > the needle deflects, correctly indicating voltage/resistance, once again - | > without the battery present. So what is the battery for then? | > | > | The only test/s that a simple analog meter (with a needle or moving finger) | should require a battery for is continuity/resistance tests. | You are correct; an analog meter will measure external sources of electrical | voltage and/or current without the battery. | However when you desire to measure an inanimate or other wise unpowered | circuit or item the source of electricity for that measurement is the small | battery inside the meter. | By the way don't try to measure any external voltage or current with the | meter set to "Ohms" or "Resistance" ranges! | For an example; holding a bulb/lamp in your hand you connect the test leads | (set to ohms/continuity etc.) to a lamp/bulb in attempt to find out if it's | 'blown' or OK? | You will not get any reading at all unless that battery is in place! | That makes sense of course because current will not flow without a source of | voltage. | BTW is this a troll? | If not suggest that a quick self paced course on basic Ohm's Law will assist | advantageous use of the meter and perhaps minimize the chances of "Blowing | the sh**" out of it! Which we have all done at one time or another. | Also read the little book that should come with the meter. There are some | applications where such a small analog meter can do better job than a more | sophisticated more sensitive one! | |
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wrote in message

What's wrong with a spare rechargable battery and a cheap charger. The way I see it you are suggesting a 1.5 volt battery be charged at a rate of 25 ma at 60 volts pulsating DC? Or did you mean 1.5V zener diode? If you were to use a *standard diode* you would be limited to about a half a volt and the battery would never charge. I think you also failed to mention the battery would have to be across only the diode. In any event it would still be a poor charger........Ross
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wrote in message

Basis of an idea there; as you suggest you'd have to modify the circuit a bit! Probably not worth while because even the simplest kind of primary cell is so cheap (25 to 50 cents?) and available and last so long. Prob. not worth doing it to a simple $6 to $15 'pocket style multimeter'? Rechargeable for a 'digital' display meter might be OK; especially if I tend to leave ours with its LCD display switched on after use!!!!! In a simple analog meter, the battery, which powers only the resistance/continuity scales, is so little used that it will last its shelf life and then some. And since meters tend to be stored in reasonable environment; unless it's in my vehicle glove box and the battery freezes, the battery will normally die of old age rather than use? In a typical analog meter, the battery supplies, and only momentarily, something of the order of one half milliamp (that's one 2000th of one amp for only the few seconds of testing!). So if it does not leak or rust away the battery will have potential for years! I've seen one or two cells that were 20 years old and still had enough potential to fully deflect the meter. After all the batteries in our smoke detectors last a year and they 'are' providing a 'constant' small drain. Keeping a spare pack of the cheapest batteries available a good idea. Also, in effect an analog meter tests its own battery; every time you check FSD for zero ohms; right? BTW on the subject of small cell batteries, including those 9v 'Transistor' style, one of the most useful and productive 'gadgets' is one of those R.Shack battery testers. Sometimes on sale for half price at around $5 to $8. Being congenitally unable to 'not tinker' with anything! Have started to modify our little battery tester, hopefully to enable one hand testing of the continuity of say fuses and/or lamps! Despite that we have several multi-meters; but justify that a combined battery/fuse/lamp tester would result in one less thing (multimeter) to carry around? :-) Suggestions: When you chuck out an old shaver save the zipped and slightly soft padded container, often just right size for a multimeter! By then the cardboard box the meter came in from Taiwan, China or Mexico will have crumbled. And; those soft padded/insulated fabric school lunch 'boxes' are an excellent container for a test instrument, test leads, low wattage AC bulb for checking mains supply, short extension cord, neon tester etc. and a couple of small hand tools. All in one package; so when your favourite Aunt Ida phones and says her lights are blinking, again, and she also needs a new bulb in her flashlight, just grab it and go. Have fun out there!
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On Sat, 26 Feb 2005 13:48:48 -0500, "Ross Mac"

Maybe it was just a "fluke?" :-)
My Fluke Model 87 uses a standard 9-volt alkaline battery, The first one lasted 9-years. The second one is going on 5-years. Are you sure we are still talking about hand-held, portable instruments? How do you recharge it? I never heard of a portable DVM with rechargeable batteries. I can't imagine being out in the field without AC power and having the meter go dead.
Dick
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On Sat, 26 Feb 2005 17:24:09 -0500, "Ross Mac"

I can only surmise that you put the rechargeable in? My Fluke 87 manual clearly does not call for rechargeable. When I got it back from Fluke after calibration, it didn't have one in then either. It had a new battery, as Fluke always puts a new one in. I have only had it recalibrated once as I am a very light and non-critical user. I am still curious as to how you charge the battery in your 87 as there is no provision for doing that. Surely, you don't take the meter apart each time.
Dick
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"Dick" <LeadWinger> wrote in message wrote:

Yes, you remove the screws and recharge it....once a year is not that often....I have never had to send the 87 in for repair and cal but the 8060A has been in several times and they have not changed the battery out....,my .02.....Ross
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On Sat, 26 Feb 2005 13:48:48 -0500, "Ross Mac"

I just checked on the Fluke website, and the very latest version of the 87, the V series, still uses the same old 9-volt alkaline as used by my 14 year old 87. If yours has a rechargeable, I am certain that someone added it after it was shipped from Fluke.
Dick
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nick,
I don't follow this. When the meter is set to measure 120 VAC the battery is not in the circuit and can not be charged, I think. Also can you safely charge non rechargeable batteries? This sounds like very bad advice, especially for a newbie.
Dave M.
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On Sat, 26 Feb 2005 16:08:45 GMT, "David Martel"

You don't want to fool with a rechargeable battery in an analog VOM. For that matter, you don't want one in a digital voltmeter either. Alkaline batteries have a shelf life of several years. As others have already pointed out, the only thing the battery is for is in measuring resistance. This reading depends upon measuring the current flow through resistors in the meter. If there is no battery, there will be no current flow. The meter would work fine for all other measurements because they generate their own source of power to operate the meter.
Dick
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"Dick" <LeadWinger> wrote in message wrote:

Why wouldn't you use a rechargeable battery in a meter? I've had one in my $400 Fluke DMM, sent out for repair and calibration and it came back with the rechargeable still in place. Apparently they didn't have a problem with it nor have I for at least 15+ years. Just curious Dick....take care, Ross
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snipped-for-privacy@ece.villanova.edu wrote:

Bad advice, and technically incorrect.
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"Dick" <LeadWinger> wrote in message wrote:

I too have Model 87 and a Model 8060A along with two Tek Scopes a couple of True RMS clamps and all of them use rechargeables. Now I must admit that I do keep a spare rechargeable in every case and I used these instruments *alot* ( now retired ). My batteries would require a recharge about once a year and I could even recharge them with my inverter in my truck (fodder for another discussion). I can't say I ever got the life out of a 9V that you did (Duracell) and I always shut the meter off when I wasn't using it and have always been surprised the switch didn't wear out...So now you got the rest of the story....but hey...we all have different use patterns and experiences.......take care Dick, Ross
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