Ever built a project out of wood and found
out later that nothing really stayed square, you found cracks or checks in
the timber used or something badly warped not long after you completed it?
Perhaps you were using lumber that was too
"wet", i.e. it had too much moisture inside. I'm sure we have all come
across the problem at some stage in our woodworking hobby or career.
And when you go down the path of trying to
use reclaimed or salvaged wood, or even some you have chopped from your
own back yard, how will you know when it is ready to be safely used?
To reduce the incidence of problems in
selecting and using "wet" wood, you really do need a moisture meter. They
range in price and features, some costing under $50, others up to a couple
hundred of dollars.
Today we are taking a look at the Wagner
MMC220. I decided to grab one for a look after hearing several good
comments on this unit from fellow woodworkers.
The Wagner MMC220
Once you pull everything "out of the box", the first thing you will
notice, apart from the fact that it ships in a nice and handy protective
carry case, is that this moisture meter lacks the metal pins found on many
cheaper moisture meter units. This is certainly not a bad thing! On the
cheaper units, you have to actually bury the small pins into a part of the
lumber you wish to test. This has the unfortunate consequence of leaving
marks in the wood you are testing. The MMC220 leaves no marks on your
lumber involving clean up later. It's
pin-less design also makes you more retailer-friendly when you can through
the local lumber yard and scan wood for moisture content before purchase
without leaving marks all over their stock!
In terms of size, the MMC220 measures 4
9/16" long, 2 3/4" wide and 1 1/16" high/deep. It fits comfortably in your
hand and is light enough (at just .37 pounds to keep in your pocket) and
to avoid any type of user fatigue. It utilizes a standard 9v battery to
power the unit. A low battery indicator will appear on the large LCD
display in the form of "LO BATT" when battery levels drop low. To help
conserve battery power, the unit will automatically switch itself off if
there has not been a significant change in reading values in the last 60
The LCD screen is easy to read and the
digits easy to decipher, even at more obscure viewing angles.
On the rear of the unit you will notice the
scanning area plate. The MMC220 has a scanning area of 1 1/2" x 2 1/2". It
uses electro-magnetic wave sensing technology for more accurate readings,
as opposed to resistance determination as used by pin meters, which is
subject to conditions that cause diminished accuracy. A maximum measuring
depth of 3/4" is listed in the manual.
The MMC220 can supply accurate moisture
readings between 5% and 30% moisture content. Ideally, you would be
looking for a moisture content around 8% - 12% in wood before you would
start building anything from it. This range is just the guide I personally
go by. It may vary depending on who you talk to, or what you have read
previously. I have had few problems using wood in this moisture range
previously anyway. The unit is capable of measuring moisture content to a
Naturally, accuracy depends mostly, among
other things, upon the user selecting the correct specific gravity (SG)
setting on the unit for the species of material they wish to measure. The
MMC220 is adjustable from 0.20 to 1.0 SG. This pretty much covers
virtually all wood species used by woodworkers. The higher specific
gravity ranges (past 0.80) can be used for exotic wood species. If you are
not sure what the specific gravity of a particular species is, the unit
ships with a small booklet containing many of the more commonly used wood
species and their specific gravity values, allowing you to readily set the
correct SG to take accurate moisture readings. The wood species listed in
the accompanying species printed guide are somewhat localized to the
United States in terms of common woods, however, this unit can be used
anywhere for any species as long as you know the SG of the wood you are
use. The On/Hold button will turn the unit on and off, by holding the
button in for a few seconds. It also acts as a Hold button. This means you
can freeze the current moisture reading on the screen. This is useful if
you need to scan wood in a hard to reach place where you cannot see the
reading. You simply lay the unit on top of the wood to test, allow it to
gauge a reading and hit the Hold button once. This freezes the reading and
you can then check the reading when you can again see the display.
The Species button allows you to adjust the
specific gravity (density) setting of the unit so accurate readings can be
taken on different timbers. You can press it once to bring up the current
SG setting. Subsequent presses will increase the SG setting by 1 point at
a time. Pushing and holding the Species button cycles the setting 10
points at a time for faster increase. Once the SG reading reaches 1.0
(displayed as 100 on the screen), it cycles back to the starting value of
0.20 SG (displayed as 20 on the screen).
Below the control buttons is a 10 place
table where you can list your most commonly used species and their SG
values for quick reference. Use a pencil or non-permanent marker to
scribble these in so you can modify them later if needed.
To actually make a moisture reading, you
simply turn the unit on, place it onto the wood to be scanned and press
firmly down to engage the scanning plate onto as much wood surface as
possible and allow the reading to stabilize. Ensure that if you are
working with material less than 3/4" that the material isn't sitting on
other material or else your reading may be inaccurate.
I tested the unit on a wide variety of
species of lumber, each time adjusting the moisture meter for the species
to be tested. As far as I could tell, accuracy was very good. I
deliberately tested woods I new were still "wet" from being freshly or
recently cut and the readings indicated a much higher moisture content
that materials I knew had been kiln dried or air dried for much longer.
The MMC220 itself is very easy to use. In
fact, I had mastered it without even needing to refer to the user manual.
However, there is some useful information to know in the manual and the
few pages it contains can be read entirely in a matter of minutes. The
MMC220, overall, is quick and efficient to use. While I would have liked a
feature to have been implemented that could scroll through your most used
set of SG values for specific species (even 5 or so species), changing the
SG (density) value was not overly troublesome or time consuming.
There is not a lot more to say about this unit. The features are
simple (which is actually a good thing in this case) and there is very
little to know to get it working correctly. My 6 year old daughter can use
it properly with no issues! In terms of accuracy, the unit is factory
calibrated. While I couldn't directly measure the accuracy, i was pretty
sure it would be quite accurate given the type of tests I had done and
knowing how well each piece of lumber I tried it on had been dried
previously. I am confident in the units repeatable accuracy. It seems much
more accurate than any pin moisture meter I have owned before.
Of course, this accuracy does come at a
price. At around US$299.00 retail, the MMC220 moisture meter is an
investment that requires a little budget consideration. But when it comes
to measuring wood moisture, and avoiding costly problems associated with
using wood that wasn't as dry as it should have been before use, I feel a
little extra dollar investment in a good moisture meter is a worthy avenue
to take for future piece of mind, and more solid and stable woodworking
Wagner do have several other (less
expensive models) in their range with similar features if you are looking
for a cheaper alternative, but be sure to check features carefully to
ensure the unit you buy will match your requirements.
Overall, however, I was very happy with the
performance of the MMC220. If you have the money, it's a definite buy
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