For the electrical engineer types amongst us:
Figuring that moisture meters are measuring some dimension of electricity is
there some way a multimeter could be used for measuring the moisture ratio
in wood? ...maybe with the application of math after taking a reading of
some property of the electrical current passing through the wood?
You know damned well that I ain't no ingineer - however, there are
available articles on transferring the results of probes attached to a
VTVM to understandable resistance readings that, when applied to
tables indicating species resistance at a certain EMC will give an
approximation of what a ninety dollar moisture meter will do.
This is why accountants and project managers sit over ingineers.
On Fri, 17 Aug 2007 20:59:23 -0400, "John Grossbohlin"
tjwatson1ATcomcastDOTnet (real email)
The problem here is "repeatability" and "correlation" of your
measurement to the wood industry wood moisture content standard. Using
anything less than a wood moisture measurement device would result is
poor results. That is, the contact surface area of the probes, the
distance between the probes will cause your results to have a high
error factor between measurements. There are other variables to
consider also but I don't want to get to technical. In addition, using
conversion tables to convert OHM's or MHO's to wood moisture content
will further erode your results. Most Resistance (OHM) or (MHO)
Conductance meters today are digital.
A VTVM (Vacuum Tube Volt Meter) I don't think they are that readily
available unless you are an old timer like me who began training in
electronics technology in 1968 and worked in that field since I
retired last year.
Anyway, I am curious of your application of the data of this
I am a retired electronics technician, learning woodworking technology
Take care all.
On Fri, 17 Aug 2007 22:52:15 -0700, "SonomaProducts.com"
An ohm-meter should do it. You'll have to devise a probe that has a couple of
contacts fixed at a certain set distance, then validate it against a commercial
instrument to get a scale (at least that's what I'd consider the easiest
practical solution, rather than trying to do it with math). I've no idea what
the commercial instruments use as measuring current, but your multimeter would
find that out easily enough.
firstname dot lastname at gmail fullstop com
I'm very curious about how this works... I was sort of hoping for a "yeah it
can be done" or "it won't work" type answer before spending any more time on
this curiosity, but the references are good too. ;~)
In the past few weeks I've ended up with nearly 1,000 bf of rough cut, air
dried wood, from four sources... about 60% of it was free and the rest I got
for $1 bf. About 20% of it is cherry, 20% walnut, 20% white oak (much
quarter sawn), 30% clear pine, and the remainder red oak and other hardwoods
(maple, ash, hickory). Most is 4/4 to 5/4, 6-12" wide and 8-12' long. Some
of the walnut runs about 10" wide and 5' long. Some of the walnut and white
oak runs up to 16/4. I think I did OK for $400...
Much of the pine will go to serve Boy Scout and Cub Scout needs. For
example, I made up about 450-500 carving blocks and a box full of bench
hooks for their camp Handicraft program. Then their are the Den projects and
possibly new patrol boxes if suitable for the chosen design.
Being practical, I figured that I'd probably have the same problem with a
moisture meter as I have with my metal detector... dead batteries whenever I
need it... it sits for months at a time. Since the multimeter gets used
regularly I keep fresh batteries in it and if it could substitute for the
moisture meter I'd be covered without having another gizmo laying around.
I down loaded the PDF and checked the FWW directory on their web site... I
have most of the issues cited so I hope to "get it" shortly!
On Sat, 18 Aug 2007 09:01:32 -0400, John Grossbohlin wrote:
Would you mind posting back with your results? Something like:
1. Insert two 1/2" brads into the wood exactly 1" apart
2. Measure resistance
3. Look on p.6 of above PDF
4. Add 1% to the results ("Two-Pin Electrode" on p.7)
etc.? I'm curious how this works out, too, and just imagining some
sort of pin-inserter/holder could be designed to make it even easier.
The typical multimeter is not sensitive enough to use as a moisture
meter for wood.
There was an article in one of the mags a while back on it.
And, there has been a discussuion or ten on the subject over on
Taunton Publishing's 'Knots" forum. You might try going there and
serching for the threads.
On Sat, 18 Aug 2007 09:01:32 -0400, "John Grossbohlin"
You can use a simple hygrometer if you've got a bit of time. Keep track of
the relative humidity of the area where the wood is stickered. Hoadley says
one point per week on 1" planks. He's a good source. When you have a chunk
that you weigh and it's the same two weeks in a row, you're as low as you
can go for your conditions. See Hoadley or the Wood Handbook if you're
interested in putting a number to it.
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