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
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...
On 2005-03-02 d02mgt$hj8$ email@example.com said:
> firstname.lastname@example.org 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
>> 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.
>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
Huh? Sorry, not clear to me what your point is here.
>please, shoot me now...
Naw - you're doing OK now.
Tom Willmon near Mountainair, (mid) New Mexico, USA
Net-Tamer V 1.12.0 - Registered
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.
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
If emailing, please let me know whether
or not you are posting the same letter.
Change domain to erols.com, if necessary.
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.
HomeOwnersHub.com is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here.
All logos and trade names are the property of their respective owners.