I'm helping a buddy of mine fix his
electrical system in
Japan before
he
sails across the Pacific and so I put this together to help with
that
endeavour. So long as I did this, though, I figured I would
share. As always, I can't solve a problem I don't know about, so
please do let me know if you spot any errors/omissions/sarcasm.
=== BLUF/TL;DR ===
* If your price-point allows it, go get yourself a Fluke 87V max or a
Keysight 1282A ($500-$800)
* If you want something cheaper, get yourself an Extech 505 (and
evaluate it at a lab-bench before you leave) or a BK Precision
2709B and a waterproof bag for it. ($100-$110)
* Make sure you have spare HRC
fuses (yes the HRC part is important)
and spare (lithium for the shelf-life)
batteries and leave those in
the bag with your DMM.
* Fluke also makes a nice set of silicone leads for $30 that I think
make the experience of using it much nicer.
=== Things I think are important ===
* Measurement Confidence: As an EXAMPLE, some
cheap meters will start
giving you false readings when the
batteries are low. If you're
fixing your
electrical system in the middle of the Pacific, do you
really want to be asking whether the
battery is low, or whether the
meter is out of spec, or ...? I think it's important to have a
piece of measurement
equipment that you actually trust.
*
Water Survivability: There are a number of "waterproof" and a few
actually-waterproof DMMs on the market.
* Manufacturing Quality: As a sortof sub-category of Measurement
Confidence, how confident are you not just that the line of DMMs is
good, but your specific DMM is good?
* Does it Explode: If you accidentally put it in a low-impedance
input measurement mode on a 470V AC signal (like the start-caps of
your air conditioner), will it break the DMM? Will it blow up in
your hands? Will it short internally and cause the leads to melt
on your hands?
* Functionality: This one almost doesn't matter. You're probably not
going to care about things like burden voltage for measuring
microamps of
current, and just about any multimeter these days will
have sufficient functionality for fixing up a
boat at sea. If
you're bringing up a new part and/or writing a driver for a snazzy
new pressure/temperature IC, then you probably do care about things
like micro-amps of
current so you can infer device state from
current-draw...but please tell me you don't plan to do that on your
next
passage...or do because you're crazy, but you're my kind of
crazy :-)
=== Source ===
My primary source of information is Dave's Blog (EEVBlog). I've seen
his videos used as
training for new-hires in the space industry even.
I find his
work credible and he has not let me down yet. So shout-out
to you, Dave, and please feel free to point out everything I'm saying
that's incorrect, incomplete, or misleading.
* DMM Overview and Intro:
* $100-ish DMM Shootout:
* Why is Fluke so expensive?:
=== Options Evaluated ===
The listed prices are all from tequipment.net
* Extech 505: $110
* BK Precision 2709B: $95
* Fluke 28ii: $570
* Fluke 87V Max: $510
* Keysight 1282A: $765
=== What I Did ===
My use-case is not limited to the
boat. I do some
electrical
engineering and so I needed a bench-top meter for things like bringing
up new integrated circuits and custom circuit boards. For that, I
bought the Fluke 28ii*. It wasn't much more expensive than the 87V,
had more-or-less the same specs, and now I have a rugged/waterproof
DMM. I also bought a Fluke 117 for general home
electrical work and as
a second benchtop meter. Next time I decide to cross an ocean, I can
always bring along my trusty Fluke 28ii which ticks all the boxes.
However, during COVID, I left the boat in its old home (San Francisco)
while we fled with the newborn infant to the lower population density
of a
Portland suburb. I did buy a DMM for the boat, but its main
use-case was to be the one that's always there so that when I made a
trip down, I'd have a good DMM available in case I needed to do
anything with the electrical system.
* As an aside, I bought a Fluke 28ii right about the time the 87V Max
was coming out and had a rather fun
email exchange with Fluke about
it. The 87V Max was more expensive, and seemed to have the same specs
as the 28ii. I emailed asking what I was missing and why anyone would
ever buy the 87V Max. The response was wonderfully candid, basically
indicating that there wasn't any good reason to do so. Turns out they
only did that because the 87V has a well-deserved reputation as being
a top-notch bench meter and people found that more enticing than the
28ii. These days, though, the 87V Max is cheaper than the 28ii, so
I'd recommend you go with that instead if you want a rugged/waterproof
Fluke.
=== Analysis ===
There are two
classes of multimeters that were evaluated: super-good
and good-enough.
In the super-good category, the three listed above are all great and
have no need for further comment. Dave Jones has thrown these things
off of buildings/dams, and taken them through the canyons of the Blue
Mountains in
Australia. They'll get the job done.
In the good-enough category, I only really ever considered two
options: the BK precision 2709B and the Extech 505. The BK (at least
WAS) made to a much higher quality standard, but isn't waterproof.
The Extech is waterproof (with some helpful silicone grease anyway),
but made to a much lower general quality standard. Again, since my
use-case only needs it to be functional at the
dock, I didn't care
about waterproofing and went with the BK. If you're doing some
passage-making and can't afford the Fluke or Keysight, then I'd
probably go with the Extech and just check it out before you leave
port, or maybe get yourself a waterproof bag for storing the BK
instead. Either choice seems fine to me.
HTH,
Harrison