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What effect does varying wood density (same species) have on MC readings?9/16
I've worked with pieces of wood of the same species that
Since moisture meters are set based on the specific gravity
Hoping Gene Wengert will weigh in on this one ...
The pin type moisture meter is not affected by wood density. However, the pinless is and so requires an adjustment for density variations if you want accurate MC values.
It is hard to give you a standard correction for density, but here is an example. Assume you have a species that has a "normal" density of 39 pounds per cubic foot--typical value for sugar maple. Actually, in the wood business we measure density by giving the specify gravity, which is the density of the wood compared to water. So, 0.63 means that the maple is 63% as heavy as water, so the dry wood will float pretty nicely. (A SG of 1.0 or larger means the wood would sink and not float.) You use the pinless meter and set the density at 0.63. You get a value of 8.1% MC. Now, if you measured another piece of maple that is 10% lighter weight but at the same MC (based on the oven test), you would find that meter would read lower--about 6.4% MC. So, knowing the SG (or density) is very important for accurate values from the pinless meter.
Although this is indeed a negative characteristic of the pinless meter, it has many advantages, including speed, ability to measure the average throughout the piece,and the lack of required temperature corrections. The pin meter is indeed sensitive to temperature, measures the highest MC along the length of the pin (or at the tip if the pin's shaft is insulated), and requires a bit more time.
Together, the two meters make an awesome, accurate MC measuring tool. (But I suggest spending $200 or more for each meter and get one made in the USA to facilitate repairs, if ever needed.)