"BobS" wrote in message
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"George" George@least wrote in message
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"BobS" wrote in message
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George,

Care to expand on that? How will having a humidity gauge help him
"calibrate" his moisture meter. The moisture meter is essentially a
megohm meter that is based on resistive readings, not on ambient or
relative humidity. I may not have enumerated my response very well but
yours doesn't make a lot of sense for calibrating a moisture meter.

Made one with an old Telco "megger" years ago, calibrated it against the
meters at the college.

Think about it. With constant or nearly constant humidity, he should
read the EMC for that RH. Differences between species would be
"corrections" to the meter.

fpl = Forest Products Laboratory http://www.fpl.fs.fed.us/

A resource URL that should be bookmarked on every woodworker's computer.
The tables in the Wood Handbook are the source for EMC-MC comparisons.

George,

Ahhhhh, you didn't say you had an outside calibrated reference (meter at
the college)..... that's cheating.....;-)

But even so, I don't think that is an accurate method since the various
species of wood need to be at equilibrium (known reference point) which he
would need a calibrated meter to read their mc to start with - which he
doesn't have (for sake of our discussion). But... he could do the old
standby of measuring their weight, then drying them slowly in an oven
until there is no more change in their weight. That requires an accurate
weighing device which I'll assume he also doesn't have (unless he's gone
postal on us...).

As for your "megger", you calibrated it against another meter that was
most likely calibrated to a standard. So without using another known
reference (calibration source) or drying the wood down and then see what
the weight difference is after they reach EMC - he has no reference point
to calibrate against that I can see but maybe I'm not thinking this
through all the way either.

In reality, the difference between the typical species most of us use is
negligible and applying the correction factor (according to my meter's
table) it may at best be +/- 2% at most. Critical if you're the one doing
the drying in a kiln but you wouldn't be using a $39 meter most likely
either. So while we've told him about his problem, we haven't exactly
given him an answer he can use, so I propose the following solution:

1. He measures a sample of wood and records his readings.
2. He then wraps the piece in Saran wrap so it is in an air tight
packaging and ships it to me.
3. I'll use my meter, adjust the reading for the species, re-wrap it and
ship it to you.
4. You then take your megger, calibrate it using the RH and any tables you
have and take a reading.
5. We then all post our readings here and he can take the average reading
and use that...

-or-

He could just say - the meter indicates that it's below 10% - close
enough, use it .............;-)

Actually that is kinda what PSI said. I emailed them and they called me.
He said that if it showed 6% on wood in my basement and top of the scale on
my arm it was doing pretty good.
I think the "solution" is to compare new wood to wood that I have had a
while. If they read the same, the new wood is okay. If the new wood reads
higher, it has to dry more. Might be all I can expect out of a $29.95 meter
(it was on sale)

Appreciate your help though.