Date: Sun, 16 Jun 2013 10:55:44 -0400
Reply-To: David Beierl <dbeierl@ATTGLOBAL.NET>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: David Beierl <dbeierl@ATTGLOBAL.NET>
Subject: Re: Multimeter Recommendations
In-Reply-To: <1371323136.91164.YahooMailNeo@web162904.mail.bf1.yahoo.com >
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Hi Anthony,
At 03:05 PM 6/15/2013, Anthony Egeln wrote:
>This is a tools post, so I hope the mods approve it off-Frydae.
[hat] Ahem. This is on-topic, but if you had doubts the way to
resolve them is to ask us, not to post it with a confession. Five
strokes with a damp noodle for you, mijneer! [/hat]
> The recent post on an LED voltmeter got me thinking about buying a
> multimeter. On Amazon they have them both digital and analog,
> ranging in price from under $10 to close to $200 (Fluke brand).
I have two fancy digital meters (Fluke and Hickock), a couple "old
standard" analog meters (Triplett) and three or four cheapo
digitals. I also have a clamp-on -->DC<-- ammeter from Sears. They
all have their places.
Very few meters have the high-amps range fused. My Fluke does, and
the fuses cost $7.50 each. SOME DAY YOU WILL TRY TO MEASURE VOLTS
WITH THE METER SET UP FOR AMPS. My record is about five minutes
after getting my first meter as a present, age ten or so. In the
fifty+ years since I've probably done it about a dozen times. You'll
be a lot less unhappy if it's a ten-dollar special that goes up in
smoke. I actually repaired the internal shunt on my $7.50 Little
Yellow Meter, and the case hadn't melted too badly. Still working for me.
> Of course, Harbor Freight has quite a few as well. Would anyone
> care to make a recommendation on a mid-range price tool? Not too
> cheap but not the very expensive professional quality.
I recommend at least one of the little yellow $7 jobbies, and a
fancier one to back it up if you feel like it.
>Digital vs. analog?
For most purposes these days you'll be better off with a digital
meter if you only have one. Even cheap digitals are probably better
than +/-1% on the DC voltage ranges.
The least you can get is a 3-1/2 digit display that shows 0.000 to
1.999. Fancier ones will show up to 3.999 or 3.999 or 4.999 (aka
2000, 3000, 4000, 5000 count display).
On analog meters accuracy is specified in +/- per cent of full scale
(!). On digitals it's +/- per cent of reading, +/- a certain number
of display digits.
> Ranges?
For the van you need:
200 mVDC
20 VDC
2000 mA DC
10 A DC (20 A is even better)
Continuity beeper. N.B. all continuity beepers are not created equal
and none of them will tell you that you have a good connection. Your
meter spec will say, but typically they sound off for anything less
than 50-150 ohms.
Diode check. It would be nice if the maximum voltage was at least
three (my Fluke is 5) but typical ones are two or less. Higher
voltages let you check LEDs -- red ones are typically around 1.8 V
and other colors higher.
That's all you actually need for everyday Vanagon stuff. Plus
alligator clips for the probe ends, a couple tee-headed pins, and
twenty feet of wire with a clip on one end.
Notice I left out ohms ranges. Your meter will have them but they're
not much use on the van. The kinds of resistance that you really
need to measure on the van are those at contacts and connectors, and
they're much too low to be measured by any normal
multimeter. That's where your 200 mV range comes in. You energize
the circuit of interest, and with its normal current flowing through
it you measure the voltage drop across the suspect connection. You
have in effect invented an ohmmeter specifically tailored for the
actual circuit you're testing; and it gives the answer directly in
terms of the effect on that particular circuit which is what you care
about anyway.
> What else to look for, or cautionary lessons written in blood or
> wasted scarce dollars.
Make sure your toolbox/carry around meter won't turn itself on
because something pressed the button. Ones with a rotary knob for
power are better that way.
Very nice to have, no order of preference:
Bar graph auxiliary display, responds much faster than the digital
readout which is typically 2-3 per second.
Display illumination
AC rejection on DC ranges and vise versa. Most digital meters do this.
AC+DC readings -- high end only.
Automatic time-out, even better if you can disable it (high-end only
for that last).
Display hold button
Min/Max reading
*Fast* Min/Max -- high end only. Catches very brief excursions with
lower accuracy.
Delta (hit the button and the reading goes to zero, then shows
changes up or down from that level).
Type K thermocouple range, even better if it comes with the
thermocouple and adaptor. That's a tiny bead on the end of a skinny
wire that can measure high temps.
To auto-range or not:
Auto-ranging meters are either very convenient or a bleeding nuisance
depending what you're doing. Make sure you can turn off the
auto-ranging if present.
Panel jacks:
Meters come wired two ways. Most but not all use a separate jack for
the current ranges
Other stuff:
Frequency counter - can use as a tach by converting the readings.
Pulse duty cycle
Capacitor ranges
Transistor checker
Data logging
Rugged construction
Industrial voltage ratings -- category III and IV
> It would be good to have one tool for both vanagon and household use.
AC volts and resistance ranges are useful in the house. Any meter
has them. The cheapest ones sometimes have only two AC ranges,
instead of duplicating the DC ranges. AC current can be handy but
it's really too dangerous for ordinary usage. Better to get a
clamp-on meter with a cord adapter if you care about measuring AC
current loads.
For AC work it's good to also have:
A solenoid-type voltage tester like electricians use. It puts a load
on the line so you won't be misled by stray leakage voltages, and the
spring-loaded plunger pulls down to indicate the voltage range.
A non-contact voltage detector. It's a pen-shaped instrument
(Greenlee and others) that will detect the presence of >/= 50 VAC in
close proximity to its end (which is shaped to insert into a wall
socket but can wave next to anything).
The other REALLY handy meter for the van:
A clamp-on meter that measures DC amps. Mine's from Sears,
Roebuck. These only appeared a few years ago, whereas AC clamp-on
meters have been around for decades. It will also do your AC current
measurements for the house. If you only have $75 to spend, put $65
into this one and $7.50 for the little yellow meter and have enough
left for the tax. Mine also does volts and ohms, but it's not really
a good general-purpose meter. But it really shines at its main job.
Yours,
David
