What is best for testing moisture content of wood, a two pin or a four pin tester?
Andy.
What is best for testing moisture content of wood, a two pin or a four pin tester?
Andy.
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.
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? ;-)
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.
You mean weight loss on drying?
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.
A Wheatstone bridge?
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.
Works for me - actually a resister,two small alligator clips, two brads, a bit of wire and a multimeter.
Deb
I don't need such gimmicks to tell me that I'm fat
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