"Ian Stirling" wrote in message
...
In uk.d-i-y Graham wrote:

"Ian Stirling" wrote in message
...
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?
--

Graham.
%Profound_observation%