DIYbanter - View Single Post - Why does Analog Multimeter need AAA Batery

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. 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.

[snip]
Getting my first Field Effect Transistor powered meter was a reall
blessing. It had something like 2 MEG ohms / volt sensitivity. Most
of the digital stuff now probably has 10 or 20 Meg ohms / volt.

No, not "per volt". That's the input resistance for DC measurements.

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