Why does moisture meter need to know the wood type?

[StoveInNH]

I don't own MM yet, mainly because I can't identify wood (other than pine and white birch).

Why do they need to know the wood type to measure the amount of moisture present?

 

[RockyMtnGriz]

Mine doesn't, though I guess there's probably something there. I bet there is some variation between species. But really, it's just an estimator IMO. Lots of variables like temperature affect the number you see.

 

[StoveInNH]

Mine doesn't, though I guess there's probably something there. I bet there is some variation between species. But really, it's just an estimator IMO. Lots of variables like temperature affect the number you see.

Which do you have?

 

[brenndatomu]

Never seen one that asked wood type, other than maybe softwood/hardwood...or firewood/lumber.

 

[RockyMtnGriz]

DrMeter MD812. Came with my Kuuma furnace. Seems to work well enough, but looks like it's no longer available?

Amazon product ASIN B00HQZYIDW

 

[StoveInNH]

Hmm..maybe I misunderstood what I was reading. I'll review!

 

[Eman85]

Probably so they can make it special and charge more for an ohmmeter

 

[stoveliker]

Resistivities of wood depends on the water content, that's what the meters are based on. However, it also depends on fiber density, structure, and thus growth rings density and width, etc.
Therefore, generally moisture meters are calibrated for some type of fir, I believe. I.e. using it on e.g. oak will give a "wrong" number.

But, as said, it's an indication, not a scientifically accurate data provider. There are precision margins in the (resistance) measurements, there is the effect of temperature (calibrated using wood at 70 F), depth of pins in the wood, etc. etc.

Given all that, using it and reading below 20% for a piece of wood near room temperature, you know you'll be good. What you won't know is what the actual precise moisture content is - but you don't need to know. "good" is enough for burning.

If you want to know the actual numbers, I would buy a proper multimeter, calibrate it carefully, and use exactly the same circumstances each time you use it. That's not feasible nor needed for normal firewood assessment.

 

[bholler]

For firewood I doubt it matters all that much. But when I was a cabinet maker I used one that auto adjusted for temperature and you entered in the species so it could adjust. But it was far from the $20 to $30 we spend on ones for firewood.

 

[Woody Stover]

I don't own MM yet, mainly because I can't identify wood (other than pine and white birch).
Why do they need to know the wood type to measure the amount of moisture present?

As mentioned, it's just a ballpark figure so you don't need to spend a lot for a meter. Harbor Fright has one for $14 that works fine.

Therefore, generally moisture meters are calibrated for some type of fir, I believe. I.e. using it on e.g. oak will give a "wrong" number.

Oh, so my Oak might be more like 28%, rather than the 40% the meter is showing? Great!! 😉😔

 

[salecker]

After a while you can tell if the wood is unfit to burn,especially if you are just dealing with one species.

 

[Woody Stover]

After a while you can tell if the wood is unfit to burn,especially if you are just dealing with one species.

Right. The common stuff here, White Ash and Red Oak, I can tell pretty easily if a split is heavy with water or not. The more dense species, White Oak and Hickory, are heavier dry than the others so it's a little harder for me to tell. Plus I don't get as much of those, they don't die as often, so I haven't handled near as many splits as the Ash and Red.
If you're splitting you can do the "lip test." Pick up a split that's been split a little while and press it to your lips or cheek--wood that's evaporating a lot of water will be cool.
Knocking splits together is a crap shoot. I've had sopping wet wood, and banged a couple splits together, and it rang like a bell, didn't thud as wet wood often will.