On 2005-03-02 said:
Newsgroups: alt.home.repair,alt.energy.homepower
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

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