Why does Analog Multimeter need AAA Batery

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snipped-for-privacy@cybermesa.net wrote:

You forget that there are different scales on the meter face. Full scale deflection on one scale may be reading 250 volts and 10 volts on another. The meter movement HAS to see the same amperage in order to get fullscale deflection. The amount of resistance you have to add will, of course, vary with each scale, but at no time can the current EXCEED the 1 ma (or whatever) at full scale.

You are right. I had ohms per volt on the brain from the previous paragraph. I was just trying to show how much less circuit loading there was with a vtvm (or FET) type of meter.
please, shoot me now...
mike
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On 2005-03-02 d02mgt$hj8$ snipped-for-privacy@reader2.nmix.net said: >Newsgroups: alt.home.repair,alt.energy.homepower > snipped-for-privacy@cybermesa.net wrote: >> > ... The really cheap meters will say something like 2 Kohm / >> >volt or 3 K ohm / volt on the face. A better quality one will >>say >something like 20K ohm / volt. These ratings are usually >>based on 1 >milliamp giving full scale deflection of the >needle. >> No, not 1 mA. >> 2 Kohm/volt = .5 mA >> 3 Kohm/volt = .33 mA >> 20 Kohm/volt = 50 microAmps >You forget that there are different scales on the meter face. No I didn't. Unless my simple, ohm's law calculations were wrong, meter movement sensitivity is 1 / ohms per volt. To set measuring range of meter you select a multiplier resistor which supplies full scale meter current at your desired full scale voltage.
A 1Kohms/volt meter would use 10K to read 10V full scale. A 20Kohms/volt would need 200K for the same range.
Full >scale deflection on one scale may be reading 250 volts and 10 volts >on another. The meter movement HAS to see the same amperage in >order to get fullscale deflection. The amount of resistance you >have to add will, of course, vary with each scale, Yup. >but at no time >can the current EXCEED the 1 ma (or whatever) at full >scale. Huh? Sorry, not clear to me what your point is here. [snip]
>please, shoot me now... >mike Naw - you're doing OK now.
Cheers.
Tom Willmon near Mountainair, (mid) New Mexico, USA
Net-Tamer V 1.12.0 - Registered
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snipped-for-privacy@cybermesa.net wrote:

I thought I had said something similar to that, in my own, obviously unclear manner. We're stuck with the designed current rating of the meter, however, so we can't vary the current for full deflection, Your formula is therefore better stated as R = V/1ma, that is supposing a 1ma movement, as before. R is the resistance needed to allow the needle to move all the way over on that particular V scale.

Yes...and 10K and 200K ohms on the 100V scale.
Ah well..sorry for any misunderstanding I may have caused/engendered/espoused/advocated or just plain originated.
mike
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Measuring resistance.
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Larry Wasserman Baltimore, Maryland
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In alt.home.repair on Sat, 26 Feb 2005 03:10:30 -0330 "Terry"

One thing is allowing you to watch a capacitor charge. Eventually the needle reaches the resistance of the circuit, not counting the capacitance.
Meirman -- If emailing, please let me know whether or not you are posting the same letter. Change domain to erols.com, if necessary.
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HvacTech2 wrote:

***** Sentenced to 2-4 years in a dry cell.
Jeff
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Jeffry Wisnia

(W1BSV + Brass Rat '57 EE)
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The mechanism that moves the needle is technically an electric motor. When you measure voltage or current, the motor is powered by the source under test. When you measure resistance, you need an independent source of power.
BB
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You would also need the battery to test Diodes and transitors.
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