Hoadley implies in one of his wood technology books a moisture meter is simply an ohm meter.Here obviously the probes have to be ground with pencil points to drive into the wood.Does anyone have any experience using an ohm meter as such?
I’m hoping to save myself some money by not having to buy a dedicated moisture meter.Small multimeters are dirt cheap at wally world.
How far to drive the probes in the wood and what are the resistance and moisture correlations?Thanks tons in advance.Roland.
Replies
I drive screws into the wood and then touch the meter of the screw heads. As for the multimeter it works off the some principle but the resistors are different. Before I go to far I have to check my reference to make sure I know what I am talking about. But in short you cannot use a multimeter.
Scott C. Frankland
Newfoundland Wood Worker
Edited 4/25/2002 2:18:45 PM ET by Scott Frankland
Two things stand out as disadvantages for your devise. The first is how are you going to calibrate it. Yes you will get some measurement but what will it mean? Unless you can establish some cross reference to various woods at various specific moisture contents, I would think the numbers you get would be more or less meaningless.
Secondly, each species has an adjustment factor (scale). If your system is different (pin distance and current level), then you will have to independently develop those correction factors. Published values might be applicable but likewise they may be proportionally off. And you will also have to develop a temperature correction scale.
Whoops - I'm about 4 years behind on this question. I just came across it as I searched Knots for test results on various moisture meters. There is a good USFS paper on the subject of electrical resistance and moisture content at:
http://www.fpl.fs.fed.us/documnts/fplgtr/fplgtr06.pdf
titled "electric moisture meters for wood" (USDA/USFS Forestry Products Lab General Technical Report FPL-GTR-6). The paper includes both resistance for various woods as a function of percent moisture and, temperature effects. So, a multimeter, pencil, and paper ought to do it. Has anybody done this who has results to share?
Steve
Reminds me of the old saying..."stepping over the dollars to pick up pennies". Most of the cost of a moisture meter would be the research that goes into finding the readings. One could get even cheaper by using the oven dry method to figure out the moisture content but it would take a long time to figure out the readings on a stack of newly purchased wood to determine if you should send it back or keep it.
I don't think it will work. Most multimeters do not have sufficient sensitivity to obtain accurate results.
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