ASTM D7438-13
(Practice)Standard Practice for Field Calibration and Application of Hand-Held Moisture Meters
Standard Practice for Field Calibration and Application of Hand-Held Moisture Meters
SIGNIFICANCE AND USE
4.1 Hand-held meters provide a rapid means of sampling moisture content of wood-based materials during and after processing to maintain quality assurance and compliance with standards. However, these measurements are inferential; that is, electrical parameters are measured and compared against a calibration to obtain an indirect measure of moisture content. The electrical measurements are influenced by actual moisture content, a number of other wood variables, environmental conditions, geometry of the measuring probe circuitry, and design of the meter. The maximum accuracy can only be obtained by an awareness of the effect of each parameter on the meter output and correction of readings as specified by these test methods. Appendix X1 is a commentary that provides explanation of the mandatory sections and discussion of historical practices. Appendix X2 addresses the influence of process and wood variables.
4.1.1 This practice provides for calibration and application of wood products that contain commercial characteristics and that reflect the manufacturing environment.
4.2 Most uses of hand-held moisture meters employ correlative (predictive) relationships between the meter reading and wood areas or volumes that exceed that of the direct meter measurement (for example, larger specimens, pieces of lumber, lots). The field calibration section of this practice anticipates the potential need for this type of sampling. These correlative uses are examined in Appendix X3.
SCOPE
1.1 This practice applies to the measurement of moisture content of solid wood, including solid wood products containing additives, that is, chemicals or adhesives, by hand-held moisture meters under conditions of end-use.
1.1.1 This practice includes calibration, use, and interpretation of meters for conditions that relate to wood product characteristics, such as nonuniform grain and growth ring orientation, and to end-use process conditions, such as moisture gradients.
1.1.2 Meters employing differing technologies may not provide equivalent readings under the same conditions. When this practice has been applied, it is assumed that the referenced meter is acceptable unless otherwise specified. Meters shall have been calibrated by Test Methods D4444.
1.2 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
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Designation: D7438 − 13
Standard Practice for
Field Calibration and Application of Hand-Held Moisture
1
Meters
This standard is issued under the fixed designation D7438; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope In-Line Dry Lumber Moisture Meters
1.1 This practice applies to the measurement of moisture 2.2 Other ASTM Sources:
content of solid wood, including solid wood products contain-
ASTM Standards on Precision and Bias for Various
ing additives, that is, chemicals or adhesives, by hand-held
Applications, 1992
moisture meters under conditions of end-use.
1.1.1 This practice includes calibration, use, and interpreta-
3. Terminology
tion of meters for conditions that relate to wood product
3.1 Definitions of Terms Specific to This Standard:
characteristics, such as nonuniform grain and growth ring
3.1.1 conductance meters—conductance meters are those
orientation, and to end-use process conditions, such as mois-
that measure predominantly ionic conductance between points
ture gradients.
of applied voltage, usually direct current. Direct-current con-
1.1.2 Meters employing differing technologies may not
ductance meters have been commonly referred to as
provide equivalent readings under the same conditions. When
“resistance-type” meters. Most commercial conductance me-
thispracticehasbeenapplied,itisassumedthatthereferenced
12 4
ters are high-input impedance (about 10 Ω), wide-range (10
meter is acceptable unless otherwise specified. Meters shall
12
to 10 Ω) ohmmeters. Their scales are calibrated to read
have been calibrated by Test Methods D4444.
directly in moisture content (oven-dry mass basis) for a
1.2 This standard does not purport to address all of the
particular calibration species and at a specific reference tem-
safety concerns, if any, associated with its use. It is the
perature.
responsibility of the user of this standard to establish appro-
3.1.2 capacitive-admittance meters—capacitive-admittance
priate safety and health practices and determine the applica-
meters transmit electromagnetic wave energy into the wood to
bility of regulatory limitations prior to use.
detect the influence of moisture in the wood on these waves as
an estimate of moisture content. Wave energy is most often in
2. Referenced Documents
the radio frequency range; hand-held meters commonly are
2
2.1 ASTM Standards:
placed directly on the wood surface.
D2915Practice for Sampling and Data-Analysis for Struc-
tural Wood and Wood-Based Products
4. Significance and Use
D4442Test Methods for Direct Moisture Content Measure-
ment of Wood and Wood-Base Materials
4.1 Hand-held meters provide a rapid means of sampling
D4444Test Method for Laboratory Standardization and
moisture content of wood-based materials during and after
Calibration of Hand-Held Moisture Meters
processing to maintain quality assurance and compliance with
D4933Guide for Moisture Conditioning of Wood and standards. However, these measurements are inferential; that
Wood-Based Materials
is, electrical parameters are measured and compared against a
D6782Test Methods for Standardization and Calibration of calibration to obtain an indirect measure of moisture content.
The electrical measurements are influenced by actual moisture
content, a number of other wood variables, environmental
1
This practice is under the jurisdiction ofASTM Committee D07 on Wood and
conditions, geometry of the measuring probe circuitry, and
is the direct responsibility of Subcommittee D07.01 on Fundamental Test Methods
design of the meter. The maximum accuracy can only be
and Properties.
obtainedbyanawarenessoftheeffectofeachparameteronthe
Current edition approved April 1, 2013. Published May 2013. Originally
meter output and correction of readings as specified by these
approved in 2008. Last previous edition approved in 2008 as D7438–08. DOI:
10.1520/D7438-13.
test methods. Appendix X1 is a commentary that provides
2
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
explanation of the mandatory sections and discussion of
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
historical practices. Appendix X2 addresses the influence of
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. process and wood variables.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
1
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D7438 − 13
4.1.1 This practice provides for calibration and application mixtures of heartwood and sapwood. Furth
...
This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
Designation: D7438 − 08 D7438 − 13
Standard Practice for
Field Calibration and Application of Hand-Held Moisture
1
Meters
This standard is issued under the fixed designation D7438; 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 Department of Defense.
1. Scope
1.1 This practice applies to the measurement of moisture content of solid wood, including solid wood products containing
additives, that is, chemicals or adhesives, by hand-held moisture meters under conditions of end-use.
1.1.1 This practice includes calibration, use, and interpretation of meters for conditions that relate to wood product
characteristics, such as nonuniform grain and growth ring orientation, and to end-use process conditions, such as moisture
gradients.
1.1.2 Meters employing differing technologies may not provide equivalent readings under the same conditions. When this
practice has been applied, it is assumed that the referenced meter is acceptable unless otherwise specified. Meters shall have been
calibrated by Test Methods D4444.
1.2 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility
of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory
limitations prior to use.
2. Referenced Documents
2
2.1 ASTM Standards:
D2915 Practice for Sampling and Data-Analysis for Structural Wood and Wood-Based Products
D4442 Test Methods for Direct Moisture Content Measurement of Wood and Wood-Base Materials
D4444 Test Method for Laboratory Standardization and Calibration of Hand-Held Moisture Meters
D4933 Guide for Moisture Conditioning of Wood and Wood-Based Materials
D6782 Test Methods for Standardization and Calibration of In-Line Dry Lumber Moisture Meters
2.2 Other ASTM Sources:
ASTM Standards on Precision and Bias for Various Applications, 1992
3. Terminology
3.1 Definitions of Terms Specific to This Standard:
3.1.1 conductance meters—conductance meters are those that measure predominantly ionic conductance between points of
applied voltage, usually direct current. Direct-current conductance meters are have been commonly referred to as
12
“resistance”“resistance-type” meters. Most commercial conductance meters are high-input impedance (about 10 Ω), wide-range
4 12
(10 to 10 Ω) ohmmeters. Their scales are calibrated to read directly in moisture content (oven-dry mass basis) for a particular
calibration species and at a specific reference temperature.
3.1.2 dielectriccapacitive-admittance meters—dielectriccapacitive-admittance meters transmit electromagnetic wave energy
into the wood to detect the influence of moisture in the wood on these waves as an estimate of moisture content. Wave energy is
most often in the radio frequency range; hand-held meters commonly are placed directly on the wood surface.
1
This practice 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.
Current edition approved April 1, 2008April 1, 2013. Published May 2008May 2013. Originally approved in 2008. Last previous edition approved in 2008 as D7438–08.
DOI: 10.1520/D7438-08.10.1520/D7438-13.
2
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
1
---------------------- Page: 1 ----------------------
D7438 − 13
4. Significance and Use
4.1 Hand-held meters provide a rapid means of sampling moisture content of wood-based materials during and after processing
to maintain quality assurance and compliance with standards. However, these measurements are inferential; that is, electrical
parameters are measured and compared against a calibration to obtain an indirect measure of moisture content. The electrical
measurements are influenced by actual moisture content, a number of other wood variables, environmental conditions, geometry
of the measuring probe circuitry, and design of the meter. The
...
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