Posted to free.uk.diy.home,rec.crafts.woodturning,uk.d-i-y
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What moisture meter
"Graham" wrote in message
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"Ian Stirling" wrote in message
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In uk.d-i-y Graham wrote:
"Ian Stirling" wrote in message
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In uk.d-i-y handy-andy wrote:
What is best for testing moisture content of wood, a two pin or a four
pin
tester?
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? ;-)
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?
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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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