stan wrote:
On Mar 30, 2:59 am, mm wrote:
On Sun, 29 Mar 2009 10:32:59 -0700 (PDT), svu geek

wrote:
I need to buy a multimeter. I noticed that for the resistance some
have 2000k and some have 20M, which I believe are totally different.
Which one is better to have? Or does it even matter? I'm mostly
interested in testing something that's around 2M.

The resistance you plan measure, 2M ?, had nothing to do with the
resistance of the meter. All multimeters can measure a wide range of
voltages, probably enough for anything you'll want, unless your
interests broaden a lot. (For example, you need a special probe to
measure the 25000 volts on a color tv picture tube, but you will
never do that. And if you need to see if there's voltage to a
picture tube, you can just put a little neon bulb in a soda straw,
and hold it near the thick wire. If it lights up, you have voltage.
)

So I don't know if
it matters which multimeter I get.

Just for the record, on an analog meter and iiuc on a digital meter,
it's 2K or 2meg ohms/volt, ohms per volt. I think that means that the
resistance in the meter circuit is 2K or 2M times the greatest value
at the right end of each analog scale. That is, the resistance
changes for each dial setting. Not sure what it means in digital, but
something parallel.

I hate to like new-fangled stuff, but I do in this case. I think you
can easily learn to ignore phantom voltages in AC current and that is
pretty much the only drawback to high impedance meters. While there
are high-impedance analog meters (Like FET-VOMs) they are quite
uncommon. Most are digital and the advantages of digital are
auto-polarity (no need to get the red and black right when measuring
voltage), auto-zeroing and auto-maximum for resistance measuring, and
for some slightly more expensive meters, auto-ranging (no need to set
a dial to the 2, 20, 200, or 2000 volt scale, etc. It figures it out)

Analog don't and can't AFAIK have any of these things.

OTOH, analog have the advantage that you can put the meter on
resistance and watch a capacitor charge or discharge. After a while,
I felt I could tell a good cap by the way the needle moved. You can
also watch a discharge with the meter on DC voltage, but iirc for all
but really small caps, it takes too long.

It's nice to have a continuity tester with a buzzer built-in, so you
don't have to look at the meter for this simple task. The very cheap
Harbor Freight meters don't have that, and maybe some others don't,
so if you want that, check if it has it.

So: With that overload of technical information by some very
knowledgeable posters it comes back to; "What do you want to use it
for?".

If just to test household stuff a reasonably cheap digital display
meter under $20 probably OK.

Learn how to use it, keep the internal battery (replaced) although
they last a long time. Although some/many digitals will shut
themselves off after a few minutes to conserve the battery, anyway.

Check that it has, or make good test leads. The sort that have
substantial rubber over a spring clip are good, so fingers don't have
to touch metal clips contacting possibly live wiring. An extra lead
and/or extension can sometimes be helpful and can be stored in the
same case with the meter.

Make sure electric power to a circuit IS turned off before using the
ohmmeter scale .... that's the one where the meter is most vulnerable
and is using it's own internal low voltage battery to test a 'dead'
circuit. You don't need to hook that setting of the meter,
inadvertently, to say a 115 volts wall outlet and blow the proverbial
you know what out of the meter!

However many do have a special small protective fuse (usually a few
milliamps) inside and some even provide a spare fuse! Resist the
temptation to 'fix' the fuse with Al foil (unless very temporarily and
you know exactly what you are doing) because next time one makes a
mistake (and we all do occasionally!) It's very easy perched on an
awkward ladder with cramp in the bad left leg to forget that you were
just testing for continuity with the ohmmeter setting; and then touch
it on 115 or 230 volts ...................... darn!!!!!!!!! That may
very well damage the meter!

In my experience, testing on the amp ranges is where the greatest risk to the
meter comes in.