I just bought a "MD-26 Timber Moisture Meter".
All the wood in my basement, be it stored hardwood or construction 2x4s,
measures 6% moisture. The wood in my 1st and 2nd story (completed projects)
do not register; presumably below 6%.
I bought the meter because I just cut and stickered a 4' high pile of
walnut, also in my basement. The wood at the bottom measures 24% and the
wood near the top of the pile measures 14%.
The meter is consistant; it will give the same reading over and over again;
but I am sure if it makes sense.
May in Rochester NY is not all that arid; my wood should not be below 6%.
And my freshly cut wood should not have gone from 24% to 14% in one week.
Do I have a defective meter, or do I not understand something? Thanks.
I'm east of you and would expect readings of 12% in a dry basement for wood
that has been stickered and stored for awhile. Tried finding that model of
moisture meter and cam up with zip. Is it a pin or pin-less model and have
you tried a fresh battery?
I get kiln-dried wood from Lakeshore Lumber near Pulaski and I check it with
my meter at the time I pick it out. They guarantee 8% or less - or it's
free (never had a chance to take him up on that either). When I sticker it
in my walk-in basement (insulated and has a dehumidifier), the wood will
slowly creep up to about 10-12% in several weeks. That's pretty consistent
across all kinds of hardwood I've purchased from them over the years.
Something does not sound right with your readings, so try this. Take two
pieces of wood, one that is at 6% or less and one that is much higher that
you can drive some nails into. Take two #8 finishing nails (shiny ones -
not coated) and drive them into the edge of the boards - not close to the
ends. The distance between the two nails should be the distance between the
pins on your meter so they will read the same. Drive the nails in about 1".
Take a measurement as you normally would, on the edge, pushing the pins of
the meter into the wood by hand and record the reading. Now take a reading
off the two nails - any difference?
If it's significant, one thing that may be causing the low readings is case
hardening. The wood was dried to fast and the outer layer is a lot drier
than the inside. Another cause of different readings is pushing the pins
into the end grain one time then into the edge of the wood the next
reading - lots of variance depending on how the wood was dried.
On construction lumber - like your 2x4, it comes from the mill at about 20%
mc and will take a good 3 months to get down to 12% in this area at this
time of the year. Try drying it faster in the basement by using a fan
blowing on it usually results in a lot of 2x4's that can be used for making
arched window frames. Need any arched 2x4's.......
Try a new battery and maybe even another meter if you can borrow one and if
the readings are still at 6% and the wood is dried properly and not case
hardened, then you found a good source. It will eventually come up to
equilibrium for this area which is 10-12% for wood stored in a dry basement.
Also keep in mind that this class of moisture meter is not going to be
extremely accurate and it's a "relative indicator", not an exact measuring
Also consider that the readings you're getting from completed projects were
(most likely) in a nice heated environment all winter and dry as hell - now.
Wait a couple of weeks (rain forecasted all next week for this area) for
your house humidity to get up to normal (RH 40% +) and measure again.
There's the answer, only poorly enunciated. Check the relative humidity in
the area where the wood is stored, then check against the table EMC for that
A "dry basement" can mean a lot of things. Mine's the 4' deep kind and is
heated, so the lumber stored there is at 4% right now - but climbing.
Dehumidifier will go on line by the beginning of June, but to maintain 55%
in the shop it won't run much save when the rains come.
You didn't mention the corrections for your meter. Most have to have them
to be even close to accurate across species.
I'm where it snowed yesterday, and the wood-burning furnace was required all
day. Probably should light it now, but it's 66 inside, and only a few below
downstairs. Just came up from there, and I am wearing short pants.
Get a humidity gage and use it to "calibrate" your meter. With pretty
constant humidity for a couple of weeks and the tables from fpl, you can
work up your own species corrections.
Care to expand on that? How will having a humidity gauge help him
"calibrate" his moisture meter. The moisture meter is essentially a megohm
meter that is based on resistive readings, not on ambient or relative
humidity. I may not have enumerated my response very well but yours doesn't
make a lot of sense for calibrating a moisture meter.
Here's but one reference
Click on the links on the side to go to individual sections for the "How To"
I'm sure there are many other references that are more up to date but this
one addresses just about everything discussed in this thread. After reading
this, I learned that your meter is most accurate in the first 2 to 3 seconds
and then the reading starts to vary with time. My suggestion of driving in
two nails cane from another site that showed how to make your own kiln and
how to monitor the mc of the wood being dried.
I believe Steve Knight made the drier and made a number of posts on this
subject and how he measured how dry the wood was by using both a weighing
method and resistive readings.
Made one with an old Telco "megger" years ago, calibrated it against the
meters at the college.
Think about it. With constant or nearly constant humidity, he should read
the EMC for that RH. Differences between species would be "corrections" to
fpl = Forest Products Laboratory http://www.fpl.fs.fed.us /
A resource URL that should be bookmarked on every woodworker's computer.
The tables in the Wood Handbook are the source for EMC-MC comparisons.
Ahhhhh, you didn't say you had an outside calibrated reference (meter at the
college)..... that's cheating.....;-)
But even so, I don't think that is an accurate method since the various
species of wood need to be at equilibrium (known reference point) which he
would need a calibrated meter to read their mc to start with - which he
doesn't have (for sake of our discussion). But... he could do the old
standby of measuring their weight, then drying them slowly in an oven until
there is no more change in their weight. That requires an accurate weighing
device which I'll assume he also doesn't have (unless he's gone postal on
As for your "megger", you calibrated it against another meter that was most
likely calibrated to a standard. So without using another known reference
(calibration source) or drying the wood down and then see what the weight
difference is after they reach EMC - he has no reference point to calibrate
against that I can see but maybe I'm not thinking this through all the way
In reality, the difference between the typical species most of us use is
negligible and applying the correction factor (according to my meter's
table) it may at best be +/- 2% at most. Critical if you're the one doing
the drying in a kiln but you wouldn't be using a $39 meter most likely
either. So while we've told him about his problem, we haven't exactly given
him an answer he can use, so I propose the following solution:
1. He measures a sample of wood and records his readings.
2. He then wraps the piece in Saran wrap so it is in an air tight packaging
and ships it to me.
3. I'll use my meter, adjust the reading for the species, re-wrap it and
ship it to you.
4. You then take your megger, calibrate it using the RH and any tables you
have and take a reading.
5. We then all post our readings here and he can take the average reading
and use that...
He could just say - the meter indicates that it's below 10% - close enough,
use it .............;-)
Actually that is kinda what PSI said. I emailed them and they called me.
He said that if it showed 6% on wood in my basement and top of the scale on
my arm it was doing pretty good.
I think the "solution" is to compare new wood to wood that I have had a
while. If they read the same, the new wood is okay. If the new wood reads
higher, it has to dry more. Might be all I can expect out of a $29.95 meter
(it was on sale)
Appreciate your help though.
You're welcome. I paid 3 times what you did and I doubt mine is any more
accurate than yours. I have now way to calibrate it against a known
standard.......unless........we both send our meters to George, then he can
sneak into the college some night and test our meters against
Nope, I could just as readily calibrated against the tables of EMC vs RH
that I referred to. The cheeseheads have done all kinds of tests to arrive
at the data, might as well take advantage of it. We stored at 45% RH at the
college (~20C/68F), giving us an 8.4%. If the meter read 8.8 at the
surface, it was in error or we checked the arrival date.
Not sure you understand that RH / EMC concept. If species A says 6% and
species B 8% in the same controlled environment which should give 7% EMC,
then you have a provisional correction of +1 and -1, respectively. Now
follow changes and increase your sample size.
As to oven drying, the advantage to NDT is the number of samples you can
take. Overall, I think this is going to be more meaningful.
Or, as I, who no longer bothers to meter, say - It's not as if drying it for
use next week will make a difference week after next.
You're absolutely right. I use the moisture meter I bought a few years back
after I got stuck with some badly dried white oak from a now defunct
supplier. I've compared readings with two other meters better rated than
mine and its close enough. It is good to have a meter though so you can
better judge the wood when someone say's "this wood has been air-dried in
the barn for x years" and it still reads 18%......
My moisture meter has a setting for different species of wood. Oak for
example, and mahogany have different characteristics that have to be
considered in calculating moisture content. Maybe you're not setting these
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