On Sun, 20 Mar 2005 19:01:50 -0500, "Eisboch"
wrote:


"Short Wave Sportfishing" wrote in message
.. .


2 - How can you make a content analysis of any material without first
starting at a reference point? If that reference point isn't zero,
then was is it?

3 - If the baseline is not zero, how do you determine what zero is?

I am very interested in your response - I wish to be enlightened.

Later,

Tom

Howdy Tom,

I was following this thread with casual interest until I realized that
moisture meter is, as the other poster suggested, really a density meter. I
am curious if it is really a ultrasonic density measuring system. I recall
that they are calibrated using calibration blocks of a material with a know
and certified density.

Howdy Sir - how's the weather?

It depends on your definition of density. Using a standard definition
of density like the mass per unit volume of a substance under
specified conditions of pressure and temperature, then no, a moisture
can't measure density in that sense.

You measure density by specific gravity - that is weighing the
material in question or determining it's relative hardness (density)
by deforming the surface or the shape of the material in some manner
and measuring the force needed to do so. Then applying some
mathematics, you have density.

As I understand it, and have demonstrated to myself by playing with
the one I have, moisture meters measure resistance. They do this by
using a 1 KHz modulated signal anywhere from 5 to 40 KHz in frequency
across a predetermined distance (centers of the probes or pads).

The presence of water would necessarily mean that there was lower
resistance, but it doesn't mean that the material is less dense.
We're not dealing with a solid block of something - this is woven and
porous fiber. The density of the fiberglass and resins isn't the
issue - it's the water in, through and surrounding the fibers and it's
penetration through the resins.

Think of it this way. If you fill a ceramic bowl with water and put
the meter pads in it, what are you measuring? The amount of water in
the bowl or the density of the bowl?

Yes/No?

Later,

Tom