Selecting a Moisture Meter

      A discussion of desirable attributes for a moisture meter used for kiln-drying quality control. June 30, 2007

Question
Anybody have a recommendation for a moisture meter that is not real sensitive about a consistent temperature (warmer than my shop typically is) and will not break the bank?

Forum Responses
(Sawing and Drying Forum)
From contributor J:
I just bought a Timber Check meter, which is simple to operate and can be had for $60. It is calibrated for 20C/68F, but it came with charts describing adjustments for other temps. Having to consult a chart is not ideal, but I think sensitivity to temperature is inevitable with electronic meters. Perhaps fancier units allow you to key in adjustment factors such as temp and species?



From contributor D:
Certainly Delmhorst, Wagner and Lignomat have stood the test of time. Over the years we have tried a number of meters and not found anything that stands up as well as these. Since meters are a very long term investment, it helps if the company making them stays around. A couple of years ago, someone from China was walking the IWF show in Atlanta and trying to sell various instruments. One was a moisture meter that would cost us about $15 and looked to be equal to anything out there at $150. He gave us 3 to try. Not one worked. Not even close.


From Professor Gene Wengert, forum technical advisor:
As some of you are aware, we ran tests on over 150 pieces of lumber using the Wagner, Lignomat and Delmhorst meters and then compared their results to the oven-dry values. The tests were done at room temperature with essentially no moisture gradients in the pieces. These three meters were quite accurate in almost all cases. (See results in the appendix in "Drying Hardwood Lumber".)

Because the density on an individual piece affects the Wagner, we did see some variation in that meter, as we did not fine tune the readings for density variation in the lumber. On the other hand, the Wagner was able to measure under 6.5% MC accurately, is very fast, allows scanning of the entire piece, and requires no temperature correction. The pin meters, which can measure gradients and have no concern about density variations, do not do well much under 7.0% MC, measure only at one spot, and require temperature correction (1% MC for every 20 F).

In truth, the best moisture meter is actually having both the pin and pin-less.

The minimum cost for a meter is around $200 if you want reliable readings and durable equipment with good resolution. Of course, if all you want to know is if the lumber is under 10% MC, then cheaper meters can be had. But I know that over-dried lumber is as bad as under-dried and that you really need to have accurate readings if you will use the readings to make some processing decisions.

We have also tested some other meters (six so far) made by other manufacturers and they often are 2 to 3% MC off. Perhaps the foreign manufacturer does not have the American species to use for calibration.

Although automatic temperature correction for the pin meters is not necessary, it is sure handy. Automatic species correction is also very desirable.

With a pin meter, it is fairly important to have insulated needles so you can measure moisture gradients and also get good readings even when there has been surface moisture regain. Most companies sell a separate probe for insulated needles.

Of course, with any meter, make sure that you can get replacement parts and service easily. I do know that two of the bigger companies (and maybe all three) will send you a replacement meter on loan if your meter breaks, so you are without a meter for 24 hours.

Finally, if you are selling lumber, it would be prudent to specify on the invoice or P.O. how you and your customer will be measuring the MC (meter brand, model). If your customers use a cheap meter, it is likely that they will get bad MC readings even though the wood is just fine.

Finally, it is critical that any meter be used. It would surprise you how often I see meters at companies that have 1/2" of dust on them.



From contributor O:
I have great luck with my Lignomat. Around $200, no problems, just change battery. Great investment.

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Have you reviewed the related Knowledge Base areas below?
  • KnowledgeBase: Knowledge Base

  • KnowledgeBase: Primary Processing

  • KnowledgeBase: Primary Processing: Air Drying Lumber

  • KnowledgeBase: Primary Processing: Kiln Operation




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