Jennifer Murphy wrote:
What should I look for in a digital multimeter for home use?

My opinion:

Must-haves:
AC volts to at least 300 V
DC volts to at least 100 V
AC and DC amps to 10 A, 15 A, or 20 A
Ohms
Continuity beeper (might be part of the Ohms function)
Detachable test leads

Nice-to-haves:
Auto-ranging
"Smart" ohms mode that will flip over into volts mode if you
accidentally probe a live circuit
Backlit LCD
Easy-to-get fuses
Easy-to-get batteries
Rubber case or holster
Hooks, straps, stands, etc.
Extra test leads, alligator clip attachments, etc.

Rationale:
Those voltage and current ranges will handle anything that a mild-
mannered homeowner will want to measure.

The continuity beeper is useful to figure out if a wire is broken or
shorted to another wire, or if an (unpowered) switch is closed or open,
without having to look at the meter.

The detachable test leads are because the leads *will* get beat up if
you use it a lot. 99% of meters use standard "banana" plugs on the
test leads, so any set of replacement leads will fit. This is kind of
an advanced use, but if you have a situation where you want to wire the
meter in for a while, you can buy banana plugs on your own and make a
custom set of leads.

However, detachable leads do make the meter more bulky; the "pocket"
meters tend not to have detachable leads. If you only use it once a
month or less, detachable leads are not such a big deal.

Auto-ranging means you just have to pick (say) "AC Volts" or "Ohms" and
the meter figures out the rest. Manual ranging means you have to choose
between (say) 4 V AC, 40 V AC, and 400 V AC ranges. It will say on the
package if it's auto-ranging, and also the big round switch on the front
will be simpler (fewer positions).

The backlit display is easier to read in the dark, which includes the
nooks and crannies of your furnace or washing machine. It uses a little
bit of battery life, though.

"Smart" ohms mode is because if you try to measure resistance on a
powered circuit, at best you'll get the wrong answer and at worst you'll
blow up the meter. Some meters detect this, beep, and flip themselves
over into measuring volts instead (which is safe for the meter).

Most all meters will have at least one internal fuse and a lot of them
have two. Eventually you *will* blow one of them, probably the amps
one. If it is a 15 A or 20 A ceramic 0.25" x 1.25" fuse, every Radio
Shack, hardware store, and electronics store in the US can supply them
(those fuses also get used in microwave ovens). If it's some weird size
of fuse, you'll have to go to an electronics store or order online. You
may have to look this up online; the packaging will say "fused for
protection", but the fuse *size* is probably only in the owner's manual.
Sometimes you get a spare fuse with the meter when new.

Most meters take a 9 V battery, but some take AAs or AAAs, and a few
take oddballs. In general the battery will last for at least several
months, and probably several years, so this isn't a super big deal. But
it's nice to be able to scrounge a battery from something else if the
meter goes dead at an inopportune time.

The case, holster, extra test leads just make it nicer to use, but
aren't *required*.

Tips:

If the test probes aren't already like this, it can help to cover all
but the last 1/8" (3 mm) or so of the metal probe tip, to avoid shorting
it out on nearby wires. You can use electrical tape, heat-shrink
tubing, or even stripped wire insulation if you can find some that is
a good force fit.

When you first get it, practice on some stuff you know the voltages of,
like flashlight batteries, a car battery, wall adapters for small
electronics, and stuff like that. You can even (very carefully) measure
your line voltage by sticking the probes in an electrical outlet.

If you get a manual-ranging one, and you have no idea what the answer
is going to be, always start on the highest range and work down. This
is less important than it was for an analog meter, but it's still nicer
for the meter to not ask it to measure something out of range.

A lot of time, the amps ranges will require that you move the red lead
over to a different socket. This is fine, but the *SECOND* you get done
using that range, move the red lead back over to its regular socket -
don't wait until later to move it back. The reason is that in the amps
range, the meter is nearly a dead short. It's *easy* to measure current
and then try to measure voltage without moving the lead back, and blow
the fuse in the meter. I've watched it being done and I've even done it
myself.

Any recommendations?

The one I use around the house is a Radio Shack 22-805, which I bought
around 1999 or 2000 because of its computer connection, but I don't use
that feature much now. It is a rebadged Metex meter. In Radio Shack's
current lineup, the 22-813 ($40) or 22-075 ($45) might do what you want.
Their 22-182 is a "pocket meter" style that is on sale for $20; that one
will get you through a lot, but if I was going to buy only one meter
from Radio Shack, I'd go for one of the other two.

My "daily driver" in my field toolbox for a long time has been a Sperry
DM8400, which I bought probably at Home Depot in about 1997. The
closest meter to that in their current lineup is probably the DM5300,
which is about $80. Their lower-priced meters may be worth a look if
they are easily available in your area.

I used to work with college students and they were unable to kill the
two Fluke 12 multimeters we had, even though they tried. The only odd
thing I ever noticed about these was that when the "low battery"
indicator came on, the calibration would be off; replacing the 9 V
battery made everything work right again. The closest current model is
the Fluke 113, but it sells for about $120; I don't think they have any
meters under this price.

I hope this helps!

Matt Roberds