Re: Stripped Down Motor

Date: Wed Feb 21 2001 - 17:01:24 PST

I don't know where you live, so the best general advice I can give is to try
Radio Shack if there's one near you. If you live in a reasonably large town
or city, there are probably other electronics stores you could also try.
Maybe your school science department has one that you could use?! Or maybe
your family knows an electrician or engineer who has one and would show you
how to use it?! Just ideas...

All meters will probably have a suitable range for measuring dc volts, but
some either don't measure dc amps, or have dc amp ranges that are too small
to be of use with this motor. I have an inexpensive digital multimeter that
has a 20 volt range, and I use that range for either one (1.5 volts) or two
(3 volts) D-cell batteries. From my experience, the maximum current used by
the motor will likely be around 2 amps, but that's just a rough value. My
multimeter has a 10 amp range, and that's what I've used -- other multimeters
might have a 20 amp range, and that's OK, but you DON"T want a meter whose
top range is less than 2 amps, and 5 amps would be a better minimum figure.
(Incidentally, the motor will use less current when running fast than when
running slow, and maybe this could actually be one of your experiments, or
test measurements.)

If you get a meter, you need to find someone to show you how to hook it up.
You connect the meter differently for measuring current than you do for
voltage, and in certain cases you may damage the meter if you hook it up
incorrectly. With one meter you won't be able to measure both current and
voltage at the same time, so you'll have to measure one, disconnect and
reconnect the meter, and then measure the other.

I'll be out of e-mail contact from around noon Thursday (Pacific Time) until
late Friday afternoon, so if you have any more questions, they have to get to
me before then.

Again, hope this helps.

Don Rathjen
Exploratorium Teacher Institute

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