ASTM D4444-13(2018)

This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation: D4444 − 13 (Reapproved 2018)
Standard Test Method for
Laboratory Standardization and Calibration of Hand-Held
Moisture Meters
This standard is issued under the fixed designation D4444; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
This standard has been approved for use by agencies of the U.S. Department of Defense.
1. Scope 2. Referenced Documents
1.1 Thistestmethodappliestothemeasurementofmoisture 2.1 ASTM Standards:
content (MC) of solid wood products, including those contain- D1990 Practice for Establishing Allowable Properties for
ing additives (that is, chemicals or adhesives) for laboratory Visually-Graded Dimension Lumber from In-Grade Tests
standardization and calibration of hand-held moisture meters of Full-Size Specimens
D2915 Practice for Sampling and Data-Analysis for Struc-
1.2 This test method makes no distinction between meter
tural Wood and Wood-Based Products
measurement technologies for standardization and calibration
D4442 Test Methods for Direct Moisture Content Measure-
requirements. Provision is made for test specimen size to
ment of Wood and Wood-Based Materials
accommodate specific meters. Appendix X1 provides an ex-
D4933 Guide for Moisture Conditioning of Wood and
planatory discussion and history corresponding to the manda-
Wood-Based Materials
tory sections. Fundamental measurement technologies are
D5536 Practice for Sampling ForestTrees for Determination
described in Appendix X2 when available.
of Clear Wood Properties
1.2.1 Meters employing differing technologies may not
D7438 Practice for Field Calibration and Application of
provide equivalent readings under the same conditions. When
Hand-Held Moisture Meters
this test method has been applied, it is assumed that the
2.2 Other ASTM Sources:
referenced meter is acceptable unless otherwise specified.
ASTM Standards on Precision and Bias for Various
Meters shall be calibrated with respect to MC by direct
Applications, 1992
measurement as determined by Test Methods D4442.
1.3 This standard does not purport to address all of the
3. Terminology
safety concerns, if any, associated with its use. It is the
3.1 Definitions of Terms Specific to This Standard:
responsibility of the user of this standard to establish appro-
3.1.1 conductance meters—Conductance meters are those
priate safety, health, and environmental practices and deter-
that measure predominantly ionic conductance between points
mine the applicability of regulatory limitations prior to use.
of applied voltage, usually direct current. Direct-current con-
1.4 This international standard was developed in accor-
ductance meters are commonly referred to as “resistance”
dance with internationally recognized principles on standard-
meters. Most commercial conductance meters are high-input
ization established in the Decision on Principles for the
12 4 12
impedance (about 10 Ω), wide-range (10 to 10 Ω) ohm-
Development of International Standards, Guides and Recom-
meters.
mendations issued by the World Trade Organization Technical
3.1.2 capacitive-admittance meters—Capacitive-admittance
Barriers to Trade (TBT) Committee.
meters transmit electromagnetic wave energy into the wood to
detect the influence of moisture in the wood on these waves as
This test method is under the jurisdiction of ASTM Committee D07 on Wood
and is the direct responsibility of Subcommittee D07.01 on Fundamental Test
Methods and Properties. For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Current edition approved July 1, 2018. Published August 2018. Originally contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
approved in 1984. Last previous edition approved in 2013 as D4444–13. DOI: Standards volume information, refer to the standard’s Document Summary page on
10.1520/D4444-13R18. the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D4444 − 13 (2018)
an estimate of MC. Wave energy is most often in the radiof- 5.2.3 Report—The report shall indicate (in the meter
requency range; hand-held meters commonly are placed di- manual, on the meter or meter scale, or on the supplied
rectly on the wood surface. reference standard) the meter model, and the electrodes for
which the standardization is valid. The sensitivity of the meter,
4. Significance and Use
the electrode assembly and the reference material, as evaluated
in 5.2.2.1, shall be reported.
4.1 Hand-held meters provide a rapid means of sampling
5.2.3.1 The manufacturer’s recommendation on frequency
MC of wood-based materials during and after processing to
maintain quality assurance and compliance with standards. of standardization shall be included in the report.
These measurements are influenced by actual MC, a number of
other wood variables, environmental conditions, geometry of 6. Calibration
the measuring probe circuitry, and design of the meter. The
6.1 General—Calibration of a meter and the electrode shall
maximum accuracy can only be obtained by an awareness of
establish reference data to adjust meter response for species,
the effect of each parameter on the meter output and correction
ambient conditions, and specimen variables, such as size and
of readings as specified by this test method.
density. Meter and electrode assemblies shall be standardized
4.1.1 This test method employs controlled conditions and
in accordance with Section 5 prior to calibration.
straight-grain, clear wood specimens to provide measurements
6.2 Calibration:
that are reproducible in a laboratory. The controlled conditions
6.2.1 Area of Measurement—Calibration shall be based,
prevent moisture and temperature gradients in the test speci-
where feasible, on the direct measurement region of the meter
men.
as supplied by the meter manufacturer. If not supplied by the
4.1.2 In laboratory calibration, the reference direct moisture
manufacturer, the area of direct measurement shall be deter-
measurements (for example, Test Methods D4442) shall be
mined by test. Every effort shall be made to quantify the
made only in the area of direct measurement of the meter. This
capability of the meter assembly to estimate moisture content
minimizes error associated with sampling of differing areas of
by reducing extraneous sources of error.
measurementbetweenthistestmethodandthatofthereference
6.2.2 Sampling and Analysis—This calibration procedure is
(Test Methods D4442).
designed for full-scale calibration of the meter and electrode
4.2 Mostusesofhand-heldmoisturemetersemploycorrela-
assembly. If only a limited portion of the scale requires
tive (predictive) relationships between the meter reading and
calibration,thenumberofequilibriummoisturecontent(EMC)
wood areas or volumes that exceed that of the direct meter
levels can be reduced to as low as two. Calibration should not
measurement(forexample,largerspecimens,piecesoflumber,
be extrapolated below the lowest value. Extrapolation above
orlots).Thesecorrelativerelationshipsarebeyondthescopeof
21 %EMCtothefibersaturationpointispermissible,provided
this test method. (See Practice D7438.)
that caution be taken in regression extension beyond the
moisture data high end point. Calculation of confidence limit
5. Standardization
envelopes are recommended with use of regression in this
5.1 General—Standardizationprovidesameasuredrelation-
fashion. Stratified sampling and analysis of variance, or both,
ship to a standard reference material that can be used to ensure
canbeappliedtoquantifysensitivitytowoodcharacteristics.If
that a meter is operating properly. Standardization shall be
the test material is other than solid wood, it shall be prepared
performed to establish the integrity of the meter and electrode.
and tested in a manner consistent with the solid wood calibra-
Standardization shall be done before calibration and use. If
tion procedures.
alternate electrodes can be used with a meter, standardization
6.2.2.1 Wood Characteristics—Wood characteristics that
shall be done for all electrode types and alternate assemblies.
need to be treated as measurement variables because they may
5.2 Standardization shall be based, where feasible, on the influence meter readings shall be represented in the calibration
direct measurement region of the meter as supplied by the sampling. Examples of these variables are density and mineral
meter manufacturer. If not supplied by the manufacturer, the content. These characteristics shall be included, identified, and
area of direct measurement shall be determined by test. measured as part of random sampling from a target population
5.2.1 If the manufacturer recommends an area, a method, or or they shall be sampled separately as part of a strategy of
astandardspecimenforstandardizationthatdoesnotreflectthe stratified sampling.
entire direct measurement area of the meter, this shall be noted 6.2.3 Sample Preparation—The sample size shall be based
as the manufacturer recommendation. on the sampling principles of Practice D2915, Section 3.4,
5.2.2 The meter circuit and electrode shall be tested with based upon subsequent subdivision of the sample into sub-sets
external reference material to verify the precision and bias in for conditioning and testing. Specimen size shall be selected to
the meter response range of anticipated use.The meter shall be encompass the direct measurement region of the meter/
evaluated over the range of environmental conditions recom- electrode assembly with minimal excess material. Specimens
mended by the manufacturer. The sensitivity of this standard- must be free of visible irregularities such as knots, decay,
ization procedure to temperature of the meter shall be part of reaction wood, and resin concentrations. The specimens shall
the evaluation. be conditioned at 25 6 1°C and selected relative humidities to
5.2.2.1 The sensitivity of the standardization reference ma- each of five EMC levels between 7 and 21 % (see Guide
terial to the range of environmental conditions in 5.2.2 shall be D4933).Alternatively, specimens may be equilibrated (follow-
evaluated. ing a desorption path) at each of the five EMC conditions.
D4444 − 13 (2018)
6.2.3.1 Species—Species shall be identified. If the sample temperature probes attached, in a sealed container. The change
represents a species group, the individual species of each in indicated MC (meter indication) shall be recorded while
specimen shall be identified if anatomically possible. changing temperature through the desired range. A final meter
reading must be made at 25 6 1°C (77 6 1.8°F) to confirm
6.2.3.2 Sapwood/Heartwood—Specimensshallbechosento
that the MC has not varied from the temperature cycling.
be entirely sapwood or heartwood, or two separate groups of
(2) Standard Temperature Correction—If a laboratory de-
each, but not mixed in the same specimens. It shall be reported
termination is not made for conductance meters, the following
if sapwood/heartwood mixing is unavoidable.
relationship shall be used to correct MC below the fiber
6.2.3.3 Wood Characteristics—Specimen selection for
saturation point over the temperature range of 0 to 40°C.
wood characteristics shall be considered in setting sample size.
0.5
6.2.4 Testing—There are two steps in the testing phase of MC 5 MC 1 0.06MC T 2 25 (1)
~ !~ !
2 1 1 2
where:
calibration. The first is meter measurements on the wood
samples following the procedures of this test method and the
MC = the MC at 25°C.
applicable criteria provided by the manufacturer. The second
This information is presented in Appendix X2.
step is conducting a direct moisture content determination
following Test Methods D4442. 6.2.5.3 Correction for Chemical Additives—Meter assem-
blies applied to wood materials that have been treated with
6.2.4.1 Meter Measurement—The equilibrated specimens
additives and have adhesives interspersed with the fiber, or
are numbered, weighed, and a meter measurement taken with
both, shall be calibrated with those materials following the
the electrode aligned on the specimen in accordance with the
precepts of this and previous sections on sampling and prepa-
manufacturers recommendation. The speed of response of the
ration. Some discretion is appropriate on temperature and
meter will determine the timing of the meter reading; manu-
moisture levels, depending on the end use of the products.
facturer’s recommendations shall be followed unless this
6.2.6 Report—The following wood sample information
variable is examined as part of the calibration process.
shallberecorded:MC,size(dimensionsineachplane),species
6.2.4.2 Direct Moisture Test—The MC of each specimen
and method of species identification, sapwood/heartwood
shall be determined by the appropriate direct method (Test
percentage, density or specific gravity, growth rate (rings/25
Methods D4442) after the meter measurement. Procedures
mm) and ring orientation, and earlywood/latewood percentage.
shall be followed to prevent moisture gain or loss from the
For other materials, the appropriate wood sample information
specimens between the meter measurement and the direct test.
shall be recorded together with adequate data to identify the
6.2.5 Correction Factor Determination—The corrections
product and its constituents. The following meter information
applied to moisture meters and the precision and bias of the
shall be recorded: manufacturer and model, reference
meters may differ significantly between the technology em-
temperature, and electrode type and configuration. The follow-
ployed and manufacturing variables. Wood characteristics,
ing standardization and calibration information shall be re-
species, temperature and chemical additives are specimen
ported:methodofanalysesandpresentation,influenceofwood
variables that may require correction factors. The following
characteristics (variables), influence of temperature and
procedures shall be followed to determine correction factors
method of correction, and details of electrode placement.
for meters.
6.2.6.1 If a meter is not accompanied by the calibration data
6.2.5.1 Correction for Wood Sample Characteristics—The
of 6.2.5 or by a discussion of sensitivity of the meter to
moisture meter scale readings determined from 6.2.4.1 proce-
operating characteristics, it shall be acknowledged that the
duresshallber
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