ASTM D7438-20
(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 will not necessarily 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 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard
1.3 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, health, and environmental practices and determine the applicability of regulatory limitations prior to use.
1.4 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.
General Information
Relations
Buy Standard
Standards Content (Sample)
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: D7438 − 20
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 D9Terminology Relating to Wood and Wood-Based Prod-
ucts
1.1 This practice applies to the measurement of moisture
D2915Practice for Sampling and Data-Analysis for Struc-
content of solid wood, including solid wood products contain-
tural Wood and Wood-Based Products
ing additives, that is, chemicals or adhesives, by hand-held
D4442Test Methods for Direct Moisture Content Measure-
moisture meters under conditions of end-use.
ment of Wood and Wood-Based Materials
1.1.1 This practice includes calibration, use, and interpreta-
D4444Test Method for Laboratory Standardization and
tion of meters for conditions that relate to wood product
Calibration of Hand-Held Moisture Meters
characteristics, such as nonuniform grain and growth ring
D4933Guide for Moisture Conditioning of Wood and
orientation, and to end-use process conditions, such as mois-
Wood-Based Materials
ture gradients.
D6782Test Methods for Standardization and Calibration of
1.1.2 Meters employing differing technologies will not nec-
In-Line Dry Lumber Moisture Meters
essarilyprovideequivalentreadingsunderthesameconditions.
2.2 Other ASTM Sources:
When this practice has been applied, it is assumed that the
ASTM Standards on Precision and Bias for Various
referenced meter is acceptable unless otherwise specified.
Applications, 1992
Meters shall have been calibrated by Test Methods D4444.
3. Terminology
1.2 The values stated in SI units are to be regarded as
standard. No other units of measurement are included in this
3.1 Definitions:
standard
3.1.1 For definitions of general terms used in this standard
related to wood and wood-based products, refer to Terminol-
1.3 This standard does not purport to address all of the
ogy D9.
safety concerns, if any, associated with its use. It is the
3.2 Definitions of Terms Specific to This Standard:
responsibility of the user of this standard to establish appro-
3.2.1 conductance meters—moisture meters that measure
priate safety, health, and environmental practices and deter-
predominantly ionic conductance between points of applied
mine the applicability of regulatory limitations prior to use.
voltage, usually direct current.
1.4 This international standard was developed in accor-
3.2.1.1 Discussion—Direct-current conductance meters
dance with internationally recognized principles on standard-
have been commonly referred to as “resistance-type” meters.
ization established in the Decision on Principles for the
Most commercial conductance meters are high-input imped-
Development of International Standards, Guides and Recom-
12 4 12
ance (about 10 Ω), wide-range (10 to 10 Ω) ohmmeters.
mendations issued by the World Trade Organization Technical
Their scales are calibrated to read directly in moisture content
Barriers to Trade (TBT) Committee.
(oven-drymassbasis)foraparticularcalibrationspeciesandat
2. Referenced Documents
a specific reference temperature.
2
3.2.2 capacitive-admittance meters—moisture meters that
2.1 ASTM Standards:
transmit electromagnetic wave energy into the wood to detect
the influence of moisture in the wood on these waves as an
1
This practice is under the jurisdiction ofASTM Committee D07 on Wood and
estimate of moisture content.
is the direct responsibility of Subcommittee D07.01 on Fundamental Test Methods
3.2.2.1 Discussion—Wave energy is most often in the radio
and Properties.
frequency range; hand-held meters commonly are placed
Current edition approved Oct. 15, 2020. Published November 2020. Originally
approved in 2008. Last previous edition approved in 2013 as D7438–13. DOI:
directly on the wood surface.
10.1520/D7438-20.
2
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
4. Significance and Use
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
4.1 Hand-held meters provide a rapid means of sampling
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. moisture content of wood-based materials during and after
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
1
---------------------- Page: 1 ----------------------
D7438 − 20
processing to maintain quality assur
...
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 − 13 D7438 − 20
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.
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 maywill not necessarily 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 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard
1.3 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 safety, health, and healthenvironmental practices and determine the
applicability of regulatory limitations prior to use.
1.4 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.
2. Referenced Documents
2
2.1 ASTM Standards:
D9 Terminology Relating to Wood and Wood-Based Products
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-Based 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
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, 2013Oct. 15, 2020. Published May 2013November 2020. Originally approved in 2008. Last previous edition approved in 20082013 as
D7438D7438 – 13.–08. DOI: 10.1520/D7438-13.10.1520/D7438-20.
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 − 20
3. Terminology
3.1 Definitions:
3.1.1 For definitions of general terms used in this standard related to wood and wood-based products, refer to Terminology D9.
3.2 Definitions of Terms Specific to This Standard:
3.2.1 conductance meters—conductancemoisture meters are those that measure predominantly ionic conductance between points
of applied voltage, usually direct current. Direct-current conductance meters have been commonly referred to as “resistance-type”
12 4 12
meters. Most commercial conductance meters are high-input impedance (about 10 Ω), wide-range (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.
3.2.1.1 Discussion—
Direct-current conductance meters have been commonly referred to as “resistance-type” meters. Most commercial conductance
12 4 12
meters are high-input impedance (about 10 Ω), wide-range (10 to 10 Ω) ohmmeters. Their scales are calibrated to read directly
in moisture content (oven-dry mass basis)
...
Questions, Comments and Discussion
Ask us and Technical Secretary will try to provide an answer. You can facilitate discussion about the standard in here.