What moisture meter

What is best for testing moisture content of wood, a two pin or a four pin tester?
Andy.
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How about no pins...
http://www.wmsconsulting.co.uk/mmc205.htm
Roy
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RzB wrote:

Good grief! That's $300 for a hobbyist grade moisture meter.
No wonder the Brits are so pale ... they're being bled to death!
Bill
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It seems especially expensive because of the weakness of the dollar.
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Andy Hall wrote:

Even at a 1:1 ratio, it would still be expensive for hobbyist use. I'm not going to get into a transatlantic whizzing contest, but simply note that I got mine (2 pin hobbyist grade) for about $40 .. not even 20 pounds. The only obvious lack is that it doesn't shut itself off.
If those on the far side of the pond think that ~150 pounds is an okay price to pay for a hobbyist grade moisture meter, then, by all means, be my guest.
Bill
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...

Try http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber300 or http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber'57 (which is what I have, I use it to compare known "dry" with un-known)
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Four pin will give more comparable results. Two pin is much more dependant on probe condition, and contact with the wood, four pin - ideally - should not depend on this.
A sharp plug cutter, an oven at 100C for an hour, and a sensitive scale is of course the best way.
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wrote:

I am guessing, but do 4-pin meters work on the same principle as those BFI bathroom scales? Sort of "Does my beam look big in this" affair? ;-)
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Graham.
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The basic theory of the two wire probes is similar to measuring the springyness of a spring, with two springy probes. It's hard to measure the springyness (resistance) of the spring, seperately from the probes, which tend to vary a great deal.
If with the four wire probes, you apply a constant tension with one set, and then measure with the other, you can get an accurate figure.
The body fat scales use a similar sort of idea - though they are designed to accurately -sort-of- measure the resistance of the thighs.
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wrote:

A Wheatstone bridge?
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Graham.
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No, that's somthing slightly different. It would work if you could guarantee that the two feet pads made identical contact, but you can't. http://en.wikipedia.org/wiki/Four-terminal_sensing is a not very good article on it. http://www.allaboutcircuits.com/vol_1/chpt_8/9.html may be more revealing.
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Graham wrote:

Works for me - actually a resister,two small alligator clips, two brads, a bit of wire and a multimeter.
Deb
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wrote:

Try these for answers. www.fpl.fs.fed.us/documnts/fplgtr/fplgtr06.pdf www.fpl.fs.fed.us/documnts/fplrn/fplrn008.pdf
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wrote:

True enough for planks. With the TDT (Turn, Dry,Turn) process, a moisture meter is absolutely unnecessary. The meter relies on continuous long grain, something not found in many places on a standard bowl form. The base or "foot" is the only place I can think of.
Better to stack such things to dry, pull when you think they should be, and then weigh them. If they weigh basically the same after a week, they're ready to turn. It's equilibrium, not absolute numbers that count.
Absolutes aren't even that important in flat work except as trend indications. If the hygrometer says the wood should be at equilibrium at 12%, and the meter shows 18, you need to wait. Of course you still follow good practice in construction, building loose with dry wood, tight with wet to accommodate seasonal changes. For me, in a heated home, that means 14% in summer and 6% or less in winter.
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Stirling wrote:

You mean weight loss on drying?
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