Multimeter as moisture meter?

Now John:

You know damned well that I ain't no ingineer - however, there are available articles on transferring the results of probes attached to a VTVM to understandable resistance readings that, when applied to tables indicating species resistance at a certain EMC will give an approximation of what a ninety dollar moisture meter will do.

This is why accountants and project managers sit over ingineers.

Regards,

Tom Watson

tjwatson1ATcomcastDOTnet (real email)

You may not be an "ingineer" but you play one hell of a round of golf. I suppose you like the woods the best.

An ohm-meter should do it. You'll have to devise a probe that has a couple of contacts fixed at a certain set distance, then validate it against a commercial instrument to get a scale (at least that's what I'd consider the easiest practical solution, rather than trying to do it with math). I've no idea what the commercial instruments use as measuring current, but your multimeter would find that out easily enough.

-P.

More important to understand the concept of EMC than have numbers.

I'm very curious about how this works... I was sort of hoping for a "yeah it can be done" or "it won't work" type answer before spending any more time on this curiosity, but the references are good too. ;~)

In the past few weeks I've ended up with nearly 1,000 bf of rough cut, air dried wood, from four sources... about 60% of it was free and the rest I got for $1 bf. About 20% of it is cherry, 20% walnut, 20% white oak (much quarter sawn), 30% clear pine, and the remainder red oak and other hardwoods (maple, ash, hickory). Most is 4/4 to 5/4, 6-12" wide and 8-12' long. Some of the walnut runs about 10" wide and 5' long. Some of the walnut and white oak runs up to 16/4. I think I did OK for $400...

Much of the pine will go to serve Boy Scout and Cub Scout needs. For example, I made up about 450-500 carving blocks and a box full of bench hooks for their camp Handicraft program. Then their are the Den projects and possibly new patrol boxes if suitable for the chosen design.

Being practical, I figured that I'd probably have the same problem with a moisture meter as I have with my metal detector... dead batteries whenever I need it... it sits for months at a time. Since the multimeter gets used regularly I keep fresh batteries in it and if it could substitute for the moisture meter I'd be covered without having another gizmo laying around.

I down loaded the PDF and checked the FWW directory on their web site... I have most of the issues cited so I hope to "get it" shortly!

Thanks,

John

Would you mind posting back with your results? Something like:

1. Insert two 1/2" brads into the wood exactly 1" apart
2. Measure resistance
3. Look on p.6 of above PDF
4. Add 1% to the results ("Two-Pin Electrode" on p.7)

etc.? I'm curious how this works out, too, and just imagining some sort of pin-inserter/holder could be designed to make it even easier.

The typical multimeter is not sensitive enough to use as a moisture meter for wood.

There was an article in one of the mags a while back on it.

And, there has been a discussui>

You can use a simple hygrometer if you've got a bit of time. Keep track of the relative humidity of the area where the wood is stickered. Hoadley says one point per week on 1" planks. He's a good source. When you have a chunk that you weigh and it's the same two weeks in a row, you're as low as you can go for your conditions. See Hoadley or the Wood Handbook if you're interested in putting a number to it.

Harbor Freight has a moisture meter for $25. Perhaps this might be an option.

The problem here is "repeatability" and "correlation" of your measurement to the wood industry wood moisture content standard. Using anything less than a wood moisture measurement device would result is poor results. That is, the contact surface area of the probes, the distance between the probes will cause your results to have a high error factor between measurements. There are other variables to consider also but I don't want to get to technical. In addition, using conversion tables to convert OHM's or MHO's to wood moisture content will further erode your results. Most Resistance (OHM) or (MHO) Conductance meters today are digital. A VTVM (Vacuum Tube Volt Meter) I don't think they are that readily available unless you are an old timer like me who began training in electronics technology in 1968 and worked in that field since I retired last year. Anyway, I am curious of your application of the data of this measurement. I am a retired electronics technician, learning woodworking technology now. Take care all. Francis