Simple moisture meter question


Ronn W

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The answer to this may be self evident but I will ask anyway to be sure........If I want to measure the MC of a piece of rough sawn lumber before I buy it, I need to plane a small area it down to relatively smooth wood if I am using a pinless meter, right?

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I don't know exactly how pinless meters work. I don't think they directly measure the moisture.  I think they use a sonor-like technology to measure the density of the object being metered.   It then compares the density of the object being measured to known species densities to back into the MC%.   At least that is how mine works.  If that is the case, I think it would be more accurate to read on a smooth surface.

 

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In my opinion, pinless meters are generally best used for qualitative rather than quantitative measurements.  I think a reasonably smooth surface is a good idea, but I've not seen this specifically mentioned in the literature on mine, which is a Moisture Encounter Plus. They simply aren't that accurate to get a reliable numeric value. Instead, they are best for comparing pieces of lumber. ie. is this piece more or less moist than other pieces in the same space?

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If the surface is slightly rough like from a band saw my meter is about 1-2% lower then a flat area. If there area areas that are ridges or deep gouges from blades it can be a lot further off and i wouldn't trust the number. Also be careful your hand behind the board can have a larger effect on your reading from a pinless then the surface roughness.

Isaac i think it depends on the pinless meter and the precision you are going after. Different wood density can throw off a pinless meter just as mineral deposits or other materials with electrical properties, could throw off a pin meter. A reading of 6% on a meter represents moisture content of 5.5% to 6.49%.

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17 minutes ago, Chestnut said:

If the surface is slightly rough like from a band saw my meter is about 1-2% lower then a flat area. If there area areas that are ridges or deep gouges from blades it can be a lot further off and i wouldn't trust the number. Also be careful your hand behind the board can have a larger effect on your reading from a pinless then the surface roughness.

Isaac i think it depends on the pinless meter and the precision you are going after. Different wood density can throw off a pinless meter just as mineral deposits or other materials with electrical properties, could throw off a pin meter. A reading of 6% on a meter represents moisture content of 5.5% to 6.49%.

Those are good points, it is certainly true that the reading inherently covers a range. The literature I've read indicate a couple points. First, moisture meters lose accuracy at the extreme ends of high and low moisture, and second, pin meters are roughly twice as accurate as pinless meters, which is why I say that pinless meters are primarily useful for qualitative rather than quantitative use. That doesn't mean they are bad tools though. I actually use one in my non-woodworking professional work routinely. 

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