View Full Version : Moisture reading vary by turning meter 90 degrees
Alan Lightstone
09-21-2010, 12:37 AM
Can't figure this one out. With a Lignomat scanner D meter, a sample of wood I tested gives a reading of 10.1% with the meter's long axis parallel to the length of the wood. When I turn the meter 90 degrees, so that its long axis is perpendicular to the long axis of the board, the meter gives a reading of 9.1%.
The boards I am measuring are 4/4 teak, about 48" x 10".
Can anyone explain why this is happening?
Neil Brooks
09-21-2010, 12:54 AM
Have you tried taking readings -- whether you hold it in the original direction OR in the 90* direction -- in various other parts of the same board ?
Maybe it's less about direction than it is inconsistency in the MC of the wood.
:confused:
Alan Lightstone
09-21-2010, 6:15 AM
Have you tried taking readings -- whether you hold it in the original direction OR in the 90* direction -- in various other parts of the same board ?
Maybe it's less about direction than it is inconsistency in the MC of the wood.
:confused:
No, it consistently has that difference throughout the board.
Ken Fitzgerald
09-21-2010, 6:24 AM
Is it the "pin" type?
Could it be that when both pins are in the same grain, the readings are higher?
Is it a digital meter or an analog meter movement?
Nelson Howe
09-21-2010, 6:47 AM
The instruction manual on mine says to run it with the long grain. I think it is calibrated for differences in resistance with and across the grain.
Nelson
John Coloccia
09-21-2010, 10:55 AM
It's because it's a pinless meter and they do that. I had a pinless Wagner that I hated. I eventually switch to a Delmhorst with pins and an analog gauge and now I'm happy again. :D
Alan Lightstone
09-21-2010, 1:58 PM
The instruction manual on mine says to run it with the long grain. I think it is calibrated for differences in resistance with and across the grain.
Nelson
Ah!!!! Never knew that.
joe milana
09-21-2010, 4:27 PM
I bought a Wagner pin-less once (Paid about $400 for it) and it about drove me nuts. Readings were all over the board (no pun intended!). It was supposed to read to a depth of 3/4" but if I hung a board over the edge of the bench and set the meter on it I would get one reading, If I waived my hand 6" below the board, the reading would change. If I rotated it 180 deg., the reading would change. If I set the board on the bench, the reading would change. I exchanged the meter for a new one and got the same results. Needless to say, I returned the meter.
Scott T Smith
09-22-2010, 9:36 AM
The instruction manual on mine says to run it with the long grain. I think it is calibrated for differences in resistance with and across the grain.
Nelson
This is correct. Additionally, you should operate a pin type meter the same way.
Chris Padilla
09-22-2010, 11:59 AM
This makes sense.
If you think about wood as a bunch of soda straws bundled together, you'll have a decent idea why they suggest reading along the grain....
Dan Hintz
09-22-2010, 12:19 PM
But wouldn't being off just a single tube/grain result in the same (or mostly same) reading as going across many tubes/grain? If the grain wall is causing the issue...
Scott T Smith
09-24-2010, 7:37 AM
But wouldn't being off just a single tube/grain result in the same (or mostly same) reading as going across many tubes/grain? If the grain wall is causing the issue...
Dan, good question. If you study wood cells, they are not round - they are oblong. Thus, there are more cell walls in a given distance "across the grain" as opposed to "with the grain". This in turn affects the amount of resistance between the probes.
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