I'm reading the reviews on Amazon of one such device and a couple of
reviewers complain that if they dip the probes into actual water, the
meter only reads 35% rather than 100%. Is this a reasonable observation
"That excessive bail ought not to be required, nor excessive fines imposed,
No. usable MC for wood is in the 10-20% range so being able to indicate
much higher than this is useless.
I only use a cheap meter as a comparator. Wood that has been in my
workshop for years can be compared to new stock and judged as to whether
it is ready to use or not.
On Friday, January 25, 2013 7:37:19 PM UTC, Tim Streater wrote:
It's nonsense. Why it's nonsense is complicated.
Rather than a moisture meter, read your copy of Hoadley's "Understanding Wood"
and get a cheap air hygrometer and some patience. Learn the key points of the
A useful moisture meter doesn't have probes and costs >$100. Probe meters aren't
as good as an air hygrometer, patience and understanding EMC.
They work just fine providing you don't try and use the probes to
penetrate the wood, they just aren't strong enough. Ideally you should
cut a section from the centre of a plank, split that in two with the
grain and take a reading from one of the split edges. IME it is often
very different from one taken near the surface, and it's the internal
moisture content you need to know.
Surely the moisture would be in equilibrium throughout the timber, so
why would a measurement at the edge be different than at the centre. If
it was wouldn't that be a sign that the wood was in the process of
It's a very common, natural and reasonable assumption that, in a fully
seasoned piece of timber, the moisture content would be the same all
over but it just isn't so.
I often receive cracked violins or guitars in the workshop and, if the
crack has been left too long (which might be weeks or months or only
days) the wood will have shrunk away from the crack making closing it
again very difficult and in extreme cases necessitating a splint of
new wood to fill the gap.
I had a Victorian Double Bass in my workshop last year. It had a split
along the belly that had shrunk away from the crack and opened out
nearly 1/8" on a piece of wood only about 3/16" thick at that point.
One might have thought that instrument would have had enough time to
The probe-type meters are measuring the conductivity of the material,
which is going to depend on the type of material as well as the water
content. (Hence different scales for wood and plaster, on some meters
If the people who dipped the probes in water (an insulator if it's
totally pure distilled water) had tried again with salt water, they
would have got a much higher 'moisture' reading.
Windmill, snipped-for-privacy@Nonetel.com Use t m i l l
J.R.R. Tolkien:- @ O n e t e l . c o m
It does rather depend on the water doesn't it !! But it also does
indicate the knowledge base of those reviewers.
Like Bob, I do wood turning and the moisture level of wood that has
been gathered in the raw is important. And like Bob I have a cheap
meter (Ebay sourced) that despite its total lack of sophistication is
surprisingly accurate. I had access last winter to two trees that had
fallen in a gale and it measured a bit over 30% for both which the
good books tells me is correct. I then part turned some of the wood
and microwave dried it, and the weight loss and moisture content
readings kept pace with one an another.
In the professional world where moisture content of many things is
critical then expensive and reliable equipment is necessary but for
the rest of us the average Hong Kong sourced meter at a tenner seems
perfectly adequate, even if only noting the change in value.
They measure the resistance of the electrolyte, which is the dissolved
salts in the remaining sap, and compare that with a look up table.
Pure water is not an electrolyte.
I see people using these meters to demonstrate the "dryness" of
firewood yet they are only measuring the comparatively dry face until
the whole log is in equilibrium. I dry samples in the microwave,
On Sat, 26 Jan 2013 20:07:54 +0000, email@example.com wrote:
The received wisdom is that you should split the wood to reveal an
unexposed surface, which should be representative of the actual MC.
The cheap meters are good enough for the job of giving an indication
of the MC of split firewood, My cheap ebay one tells me that the lump
of sopping wet "seasoned" firewood is actually sopping wet by saying
HH on the scale. (40% is the highest reading).
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