Moisture Meters?

[Ron Nossaman]

> You're right, EMC is important only in that it predicts dimensional change. If 
> you want to know the dimensional change, measure the dimensional change...duhh

"Simple" is the part we hustle past looking for the more 
difficult answer and the shinier tool.


> Ron, did you calibrate you're sample using the standard shrinkage/expansion 
> charts?

Nope, I asked the wood directly. Make up a cross grain spruce 
strip for the meter, maybe a foot long, and another identical 
one (test piece) just short enough to be measurable with a 6" 
digital caliper. Make them from the same plank, something of 
as uniform a grain density as you can find. Make the frame and 
dial indicator mount and have everything ready to assemble 
before you start finding the MC and expansion rate of the 
sample, so you can do all this before the MC in the real piece 
changes. Measure and weigh the test piece. You don't have a 
very big sample to work with, so accuracy is important. I used 
a little reloading scale, and got the weight in grains, but 
tenths of a gram on a digital scale should be fine enough. 
Once you have the length and weight of the sample, dry it in 
an oven at something around 200°F until the weight quits 
changing. Might take an hour or two. When the weight quits 
changing, moisture content can be considered to be zero. 
Measure and record the dry weight and length. The MC% of the 
strip you'll use for the gage is figured from the data gotten 
from the test piece as (wet weight - dry weight)/ dry weight * 
100. The dimensional change rate is calculated from the same 
data as a 0.001" per 1" per MC%, and the gage strip is 
anchored in it's frame at an appropriate distance from the end 
so that it will respond at 0.010" per MC% over it's length. 
Set the dial indicator in the frame so the MC reading 
corresponds to what your test data said, and you're there. Oh, 
I capped the strip with a strip of maple where the dial 
indicator plunger rides, so it wouldn't indent significantly 
over time.




> Your gizmos officially qualify to to be referred to as 
> elegant....congratulations, and thanks.
> 
> Jim I

You bet. I want to see the new gage when it's built. <G>
Ron N