Insulated pins vs. non isulated pins?

[customsawyer]

I have the J2000X moisture meter. I have a mixed load of lumber in my L200 Nyle kiln. It was all air dried below 20%. I have maple, sycamore and red oak in the kiln. When I use the non insulated pins I am getting readings around 8-9% but when I drive the longer insulated pins into the lumber I am getting 14.5-15.7% readings. All of the lumber is 4/4 thick and the red oak air dried the longest. Which set of pins is accurate? It's only about a half load.

[Den-Den]

There is a chance that both sets of pins are accurate; the surface is probably drier than the interior of the lumber.

[customsawyer]

If I am pushing the non insulated pins in a ½" into a 4/4 board then both sets of pins should only be reaching and reading the middle of the lumber.

[Den Socling]

The pins are measuring resistance. Uninsulated measure resistance between shell and shell and core and core. Insulated measure resistance at the core.

[bkaimwood]

I've constructively argued this point on more than one occasion, with no conclusion that truly made sense of it all. Voltage travels the path of least resistance, ohms law, no arguing about that. Water/moisture is an excellent conductor. Having said that, uninsulated pins should technically still read the highest MC in the test sample, presumably the core...the only exception would be the limitations of the source, being the available amperage/voltage supply, in said case, the moisture meter's battery...if the supply voltage runs out of steam before it reaches the wettest area, it has little choice but to cross over to the other pin, resulting in the reading....

[GeneWengert-WoodDoc]

The truth is that the pins measure at the tips mainly. In fact, you can cut a slot or groove between the two pins and still get the same mc. Also, the distance between the pins is not critical...variations do not change the MC.  So, the simple Ohm's law does not apply in this case precisely. I can write more if desired. Check
http://www.treesearch.fs.fed.us/pubs/9823

In your case, the deeper insulated pins read at the tips which is the core. The Uninsulated shorter pins read the wettest spot along their length. One wetter spot is all it takes to get a high reading. These uninsulated pins do not average along their length.  So, in kiln drying, their MC will most often be at the ends or deepest part of the needle.  In air drying, they may messer the surface MC if there was moisture gain.

[Den Socling]

Uninsulated pins would have to be measured as resistances in parallel. Gene says you can physically separate down to the tip and still see the same reading which has to mean that the moisture meter isn't accurate enough to measure the difference.

[Den Socling]

And for the record, water is not a good conductor. If the water molecules are combined with other elements, they can become conductive. But the meter is still reading a huge resistance.

[bkaimwood]

Yes Den, pardon the broad, non scientific statement....it's all the stuff typically found in most water we contact on a daily basis that makes it conductive... including moisture in lumber. But excluding distilled water and such. You previous post suggests a meter with poor accuracy...which in turn refers to many other threads on accurate meters, which meter to buy, conditions discussed here, and other conditions encountered. I get frustrated with it at times, wondering occasionally where the MC really is and how that determination was made, using what. I have a $60 dollar general pinless meter that has been compared to meters costing 10 times more than it...the readings are the same. Are those meters any better...I did mention constructive debate, right? I guess the only consistent proven method is the oven test? But have read of issues there, too. I over think things, sometimes a good thing, sometimes not...

[Den Socling]

I don't mean to say the meters have poor accuracy. I mean that the resistance is so high that a little more or a little less doesn't mean anything to the readout.

[GeneWengert-WoodDoc]

Den is right about resistance being very high.  That is why the wettest spot on a pin can have 10x more resistance than the spot that is 5% MC drier.  So, the uninsulated pin does not see anything but the wet spot, for all practical purposes.  In a solar kiln, due to the high humidity at night, uninsulated pins will read much higher than the truth as the surface MC is very high.

There is a comparison of two pin meters to oven dry MC for supposedly kiln dry wood in the appendix of Drying Hardwood Lumber.  I did have an inexpensive meter in the test too, but it was so far off, that I eliminated it.  Many foreign made meters with species correction or temperature correction are way off, so "made is USA is best."  The two meters are quite close indeed. 

As you spend more, you get a better piece of equipment up to about $200.  Above that you get more fancy stuff like auto species, memory, statistical calculations, lighted screen, internal calibration, etc.  the companies that sell them support kiln associations, etc.  plus they offer free loaners if yours gets run over and needs repair, etc.  kinda like comparing a Ford Fiesta to a Ford Explorer.  Both have a/c, go 70 mph, get from here to California at the same time, but the Exlorer rides more comfortably and is easier to steer, and safer.  I have seen some Delmhost meters that are as old as I am that still work, but today's meter use smaller batteries, and no electronic tubes, etc.

[bkaimwood]

Thanks for clarifying, Den...makes me not have to over think another thing😃
Gene...thanks for the general moisture meter review...simple, without too much detail or confusion, is what it is, great comparisons...reinforces what I'm using is fine. Your statement about uninsulated pins reading the wettest spot further supports my view of how ohms law applies to all the things discussed. The wettest spot is the path of least resistance. I'm hard headed when it comes to such...I spent 25 years in the auto industry, specializing in electrical, electricity, computer related, circuitry issues, amongst other things...blah blah blah...so knowing ohms law was a subconscious part of my daily tasks, and throwing it out the window, or saying it doesn't apply, just isn't in my vocabulary. I haven't found a situation where that's true...yet. After all, it's a law?😃

[Den Socling]

With a resistance (pin) meter, species and temperature compensation is worth the investment. With capacitive (pinless) meters, species selection should be available.

[bkaimwood]

What is your favorite make/model meter, Den?

[Den Socling]

I have a J2000 which I rarely use because I can check wood a lot faster with a Wagner. I have an L612 I wouldn't recommend because it has features I never use. A basic Wagner is what I recommend. BTW I don't know if it is still the case but it used to be that Wagner capacitance meters could be damaged if you slid them across dry wood. Static electricity.

[bkaimwood]

I did read that about the Wagner, and haven't heard anywhere or read anywhere that it has changed. Thanks for the recommendations.

[GeneWengert-WoodDoc]

Not true unless perhaps real close to a planer or sander.

[Den Socling]

I disagree. A long time ago with my first vac kilns, an operator would get on top of the load and "sweep" with a Wagner. One day a meter quit working and we sent it back for repair. It happened again later and when we sent it back, Wagner said it was static discharge from the "sweeping" and they wouldn't repair for free again. Lift the meter and set it down at the new location.

[GeneWengert-WoodDoc]

I cannot understand this.  Del Wagner (inventer and owner) and I slide the meter across many pieces of wood together without an issue.  The written instructions I have for my two meters make no mention of this.  We did this sweeping in a video they sponsored and reviewed.

Maybe you had lumber from a lightning struck tree and the static charge had not yet disappeared.  Or maybe it is your wonderful electrically charged personality.

[Den Socling]

Maybe it was just a repair technician looking for an excuse for the failures.

[LeeB]

Sir, I think you have your answer.  ;)

[bkaimwood]

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