moisture meters

[Gary_B]

 I am looking into buying a moisture meter, any suggestions for a meter that does the job without costing so much. I have been looking at the wagner line, but once again the 220 sells for like 269.00, I would like to find a meter that is pretty basic, I really dont need to know the moisture content of a piece of Ebony, just common species.

[DanG]

That seems a little pricey to me.  At the other end of the spectrum,  Harbor Freight has one for twenty bucks.  That seems a bit TOO cheap, but I might buy one anyway. ;)  Basically, a moisture meter is just an ohmmeter calibrated to measure moisture.  When I was working for Sprint, I had a very expensive Fluke meter on my truck.  I did a little comparing with my own $15 multimeter from Autozone and found no difference.  Durability seems to be the biggest factor, as far as I can see.

Now that I've crawled out on this skinny limb, maybe someone who actually knows something will either come rescue me, or cut the limb off behind me. :D :D

[oakiemac]

I have an el-cheapo meter but just bought a good Delmhorst J-200 for around $250. There is a big difference in the meters. With the Delmhorst I get an accurate reading in to the 1/10th of a %. With the cheapo meter I have an LED that lights up for every 2 % MC. I also can input the temperature and species and it gives a correct reading where with the ceapo I have to look on a chart and then calculate the readings.
The ceapo works if you just want a general idea of MC but if you are kiln drying or want an accurate reading I'd go with the better meters.

[Carl_B]

I have a wagner 205 moisture that I  like they sell for a little under $ 200.00  I tryed a cheaper meter and was not happey with it.

[Gary_B]

 I appreciate all the advice, I had better save up alittle and try to get a better grade meter, I know I will be in the woodworking business for the rest of my life. its kind of like and addiction that grows and grows, Im not in the high production mode, just  sawing and drying lumber for the 100's of projects my wife has come up with. But thats the good part when I need that special tool...she understands :D

[Den Socling]

Moisture meters are of two types. One works from resistance and the other capacitance. Delmhorst are resistance-type and Wagner are capacitance-type.

Measuring resistance of wood can't be done with a regular ohmmeter because the resistance is so high and the change with MC is so small.

Cheap meters give you cheap readings. The 'base' resistance varies with species. It also varies with temperature. More expensive meters have circuitry which will correct the reading for these variations in species and temperature. The 'base' capacitance varies with species. It can also, unfortunately, vary with density variations from one end of a board to the other.

I have a J2000 with a list price around $265 and a L612 that cost me around $1000. Sometimes they agree and sometimes they don't.

The resistance type use pins and leave holes. You are measuring the MC between those two pins. The capacitance type, if they are powerful (and expensive) can reach an inch or more into thick pieces and give you a reading over an area.

They both have good points in certain circumstances. That is why I need both.

[rvrdivr]

The capacitance type, if they are powerful (and expensive) can reach an inch or more into thick pieces and give you a reading over an area.

How does it "reach" into the wood? Are these the meters of choice you all are using, or are the pin types ok too?

I have one of those cheapys from Harbor Frieght and it works ok to give you a basic idea where your MC is. It is not very accurate. After a few months it stopped working, I found the lead wire from the battery terminal popped off. An easy fix, but what do you expect for $25.00. :D

[beenthere]

How does one tell or know if the meter is 'accurate' or not, or whether it is 'precise' or not?
I would guess the only way to tell is by cutting up some wood samples (kiln drying or air drying test boards) and oven drying the pieces after weighing, and then weighing again after oven drying. Any other way?

Capacitance is like an electric field similar to the 'field' of a magnet. That's about as technical as I can get 
But the 'reach' is dependent upon the size and power of the field set up. There is a difference in the readings across the grain vs. along the grain, and a company in Washington (Metriguard)  makes a grain-direction device that will provide grain angle. I believe the 'strength' of the signal is dependent upon the moisture that is in the wood. Not sure how the density of the wood affects that signal strength, which would mean a correction for wood density.

I've long heard that density variations can be easily determined IF the moisture content is known. Likewise, moisture can be measured easily IF the density is known.

[Den Socling]

'Good' meters come with calibration verification blocks.

With Wagner-type meters, wood is a capacitor and the capacitance increases with moisture content.

[rvrdivr]

A capacitor stores a charge of electricity, so if the woods a capacitor your meter is mesuring the flow of electricity into the wood ??? Without pins, what does it use to "reach" into the wood ???

[Den Socling]

I was thinking about this the other night and ended up thinking about metal detectors. I'm no EE but I think they are similar. A metal detector sends out an electro-magnetic field and looks for distortion (metal) when the field collapses. A metal detector must send out a field whose collapse is slowed by capacitance. Any electronic engineers among us?  :P

[beenthere]

Here is an early report about capacitance and moisture measurement.

http://www.fpl.fs.fed.us/documnts/fplgtr/fplgtr06.pdf#search='Capacitance%20wood%20grain';

[Den Socling]

Thanks for everything you ever wanted to know.  :D As I guessed, the frequency of the oscillator is changed by the dielectric field - wood & water.

[Gary_B]

Thanks for all the advice, I just ordered a Harbor freight one last night, I know its not one of the best, but maybe it will give me and idea of how much moistue the lumber is holding.....
                                        Gary