On 11/11/2007 2:28 PM Don Hanson wrote:

> Why the hell does a multimeter even have a fuse, any
> how?

Great question! Simply put, your basic multimeter is a voltmeter. In order
to measure current, a small resistance is typically placed in series with
the current flow and the voltage that the current develops across that
resistor is read on the meter. For example, a 1 ohm resistor will develop
1 volt across it when 1 amp is flowing through it. But anyway, the
resistors can only handle so much current without frying so a fuse is put
inline to keep from smoking the resistive bits. If the resistor was made
into a high value to limit current the current measurement would be
inaccurate. So low resistance for accuracy, which means high current is
possible, which means that smoke can happen. Smoke is evil, so we fuse.

When using the meter as a voltmeter, you switch it into high-resistance
mode so there is almost no current flowing through it because we don't
want to disturb any currents or voltages, just measure the existing
voltages. In this case no fusing is needed.

There. An answer that only someone who already knows electricity could
understand, while leaving those who don't still in the dark. My work is
done. (Dusts off hands and walks casually out of the room, whistling
tunelessly.)

Most of my meters have blown fuses. Usually some awkwardly odd size that
can never be found locally.

--
Mike "Rocket J Squirrel" Elliott
71 Type 2: the Wonderbus
84 Westfalia: Mellow Yellow ("The Electrical Banana")
74 Utility Trailer. Ladybug Trailer, Inc., San Juan Capistrano
KG6RCR