Accurate
Technology
Pro-60
Page
7
of
12
SPECIES CORRECTIONS
The dry specific gravity (density) values for a species are based on the best, current
world data, and are used to determine the species correction factor within the meter.
The values provide average density values for the species. A coefficient of variation
(COV) of about 10% describes the variability inherent in many common domestic (US)
species.
If the specific gravity of your lumber is not listed in the Species Settings Tables
provided or you are dealing with an unknown species, the value may be determined by
referring to the "Determining the Specific Gravity" section of this manual. Additional
resources are: the Forest Products Lab at http://www.fpl.fs.fed.us/ and the Wood
Handbook at:
http://www.fpl.fs.fed.us/documnts/fplgtr/fplgtr113/fplgtr113.htm
The Pro-60 meter can be used to measure non-wood materials if the density is similar
to wood products. Non-wood species can be measured by using the meter reading as
a relative value such as in “go/no-go” applications, or when determining if one
measurement area contains more moisture than another, i.e. measurements that do
not require a high absolute accuracy. SG formulas can’t be applied to non-solid wood
species due to the presence of glues and resins, which cause a non-linear moisture
content curve. If greater accuracy is required, the ASTM oven-dry procedure can be
used to determine a meter correction value for non-solid woods.
Commentary on Species Adjustment
In 1992, a study was conducted at the Forest Research Laboratory of Oregon State
University on species correction for the Wagner Hand-Held Moisture Meters. The
species tested were Douglas Fir, Lodgepole Pine, Western Red Cedar, Western
Hemlock, White Fir, Western Larch, Engelmann Spruce, and White Oak. Three to four
40-piece samples of each species were tested. Specific gravity was found to be the
primary factor on species adjustment. A species equation as a function of specific
gravity and the meter reading was obtained using multiple-regression technique (R-
square = 0.95) as follows:
AF = 8.77 + (0.25 * MM) – (15.86 * SG) – (0.62 * SG * MM) in which
AF = Species Adjustment
MM = Meter Reading
SG = Specific Gravity in oven dry weight and 12% moisture-content volume basis.
The species adjustments provide the adjusted moisture measurements that are based
on the species adjustment determined using the species adjustment equation, with
rounding to the nearest 0.5.