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.

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.

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.

A 1Kohms/volt meter would use 10K to read 10V full scale.
A 20Kohms/volt would need 200K for the same range.

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