1、Designation: D4444 08D4444 13Standard Test Method forLaboratory Standardization and Calibration of Hand-HeldMoisture Meters1This standard is issued under the fixed designation D4444; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision,
2、the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript 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. Scope1.1 This test method applies
3、to the measurement of moisture content (MC) of solid wood products, including those containingadditives (that is, chemicals or adhesives) for laboratory standardization and calibration of hand-held moisture meters1.2 This test method makes no distinction between meter measurement technologies for st
4、andardization and calibrationrequirements. Provision is made for test specimen size to accommodate specific meters. Appendix X1 provides an explanatorydiscussion and history corresponding to the mandatory sections. Fundamental measurement technologies are described inAppendix X2 when available.1.2.1
5、 Meters employing differing technologies may not provide equivalent readings under the same conditions. When this testmethod has been applied, it is assumed that the referenced meter is acceptable unless otherwise specified. Meters shall be calibratedwith respect to MC by direct measurement as deter
6、mined by Test Methods D4442.1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibilityof the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatorylimitations pr
7、ior to use.2. Referenced Documents2.1 ASTM Standards:2D1990 Practice for EstablishingAllowable Properties for Visually-Graded Dimension Lumber from In-Grade Tests of Full-SizeSpecimensD2915 Practice for Sampling and Data-Analysis for Structural Wood and Wood-Based ProductsD4442 Test Methods for Dire
8、ct Moisture Content Measurement of Wood and Wood-Base MaterialsD4933 Guide for Moisture Conditioning of Wood and Wood-Based MaterialsD5536 Practice for Sampling Forest Trees for Determination of Clear Wood PropertiesD7438 Practice for Field Calibration and Application of Hand-Held Moisture Meters2.2
9、 Other ASTM Sources:ASTM Standards on Precision and Bias for Various Applications, 19923. Terminology3.1 Definitions of Terms Specific to This Standard:3.1.1 conductance metersConductance meters are those that measure predominantly ionic conductance between points ofapplied voltage, usually direct c
10、urrent. Direct-current conductance meters are commonly referred to as “resistance” meters. Mostcommercial conductance meters are high-input impedance (about 1012 ), wide-range (104 to 1012 ) ohmmeters.3.1.2 dielectriccapacitive-admittance metersDielectricCapacitive-admittance meters transmit electro
11、magnetic wave energyinto the wood to detect the influence of moisture in the wood on these waves as an estimate of MC. Wave energy is most oftenin the radiofrequency range; hand-held meters commonly are placed directly on the wood surface.1 This test method is under the jurisdiction of ASTM Committe
12、e D07 on Wood and is the direct responsibility of Subcommittee D07.01 on Fundamental Test Methodsand Properties.Current edition approved April 1, 2008April 1, 2013. Published May 2008May 2013. Originally approved in 1984. Last previous edition approved in 20032008 asD4444 92 (2003).D444408. DOI: 10.
13、1520/D4444-08.10.1520/D4444-13.2 For referencedASTM standards, visit theASTM website, www.astm.org, or contactASTM Customer Service at serviceastm.org. For Annual Book of ASTM Standardsvolume information, refer to the standards Document Summary page on the ASTM website.This document is not an ASTM s
14、tandard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Becauseit may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all c
15、ases only the current versionof the standard as published by ASTM is to be considered the official document.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States14. Significance and Use4.1 Hand-held meters provide a rapid means of sampling
16、MC of wood-based materials during and after processing to maintainquality assurance and compliance with standards. These measurements are influenced by actual MC, a number of other woodvariables, environmental conditions, geometry of the measuring probe circuitry, and design of the meter. The maximu
17、m accuracycan only be obtained by an awareness of the effect of each parameter on the meter output and correction of readings as specifiedby this test method.4.1.1 This test method employs controlled conditions and straight-grain, clear wood specimens to provide measurements thatare reproducible in
18、a laboratory. The controlled conditions prevent moisture and temperature gradients in the test specimen.4.1.2 In laboratory calibration, the reference direct moisture measurements (for example, Test Methods D4442) shall be madeonly in the area of direct measurement of the meter. This minimizes error
19、 associated with sampling of differing areas ofmeasurement between this test method and that of the reference (Test Methods D4442).4.2 Most uses of hand-held moisture meters employ correlative (predictive) relationships between the meter reading and woodareas or volumes that exceed that of the direc
20、t meter measurement (for example, larger specimens, pieces of lumber, or lots). Thesecorrelative relationships are beyond the scope of this test method. (See Practice D7438.)5. Standardization5.1 GeneralStandardization provides a measured relationship to a standard reference material that can be use
21、d to ensure thata meter is operating properly. Standardization shall be performed to establish the integrity of the meter and electrode.Standardization shall be done before calibration and use. If alternate electrodes can be used with a meter, standardization shall bedone for all electrode types and
22、 alternate assemblies.5.2 Standardization shall be based, where feasible, on the direct measurement region of the meter as supplied by the metermanufacturer. If not supplied by the manufacturer, the area of direct measurement shall be determined by test.5.2.1 If the manufacturer recommends an area,
23、a method, or a standard specimen for standardization that does not reflect theentire direct measurement area of the meter, this shall be noted as the manufacturer recommendation.5.2.2 The meter circuit and electrode shall be tested with external reference material to verify the precision and bias in
24、 the meterresponse range of anticipated use. The meter shall be evaluated over the range of environmental conditions recommended by themanufacturer. The sensitivity of this standardization procedure to temperature of the meter shall be part of the evaluation.5.2.2.1 The sensitivity of the standardiz
25、ation reference material to the range of environmental conditions in 5.2.2 shall beevaluated.5.2.3 ReportThe report shall indicate (in the meter manual, on the meter or meter scale, or on the supplied reference standard)the meter model, and the electrodes for which the standardization is valid. The
26、sensitivity of the meter, the electrode assembly andthe reference material, as evaluated in 5.2.2.1, shall be reported.5.2.3.1 The manufacturers recommendation on frequency of standardization shall be included in the report.6. Calibration6.1 GeneralCalibration of a meter and the electrode shall esta
27、blish reference data to adjust meter response for species,ambient conditions, and specimen variables, such as size and density. Meter and electrode assemblies shall be standardized inaccordance with Section 5 prior to calibration.6.2 Calibration:6.2.1 Area of MeasurementCalibration shall be based, w
28、here feasible, on the direct measurement region of the meter assupplied by the meter manufacturer. If not supplied by the manufacturer, the area of direct measurement shall be determined bytest. Every effort shall be made to quantify the capability of the meter assembly to estimate moisture content
29、by reducingextraneous sources of error.6.2.2 Sampling and AnalysisThis calibration procedure is designed for full-scale calibration of the meter and electrodeassembly. If only a limited portion of the scale requires calibration, the number of equilibrium moisture content (EMC) levels canbe reduced t
30、o as low as two. Calibration should not be extrapolated below the lowest value. Extrapolation above 21 % EMC tothe fiber saturation point is permissible, provided that caution be taken in regression extension beyond the moisture data high endpoint. Calculation of confidence limit envelopes are recom
31、mended with use of regression in this fashion. Stratified sampling andanalysis of variance, or both, can be applied to quantify sensitivity to wood characteristics. If the test material is other than solidwood, it shall be prepared and tested in a manner consistent with the solid wood calibration pr
32、ocedures.6.2.2.1 Wood CharacteristicsWood characteristics that need to be treated as measurement variables because they mayinfluence meter readings shall be represented in the calibration sampling. Examples of these variables are density and mineralcontent. These characteristics shall be included, i
33、dentified, and measured as part of random sampling from a target population orthey shall be sampled separately as part of a strategy of stratified sampling.6.2.3 Sample PreparationThe sample size shall be based on the sampling principles of Practice D2915, Section 3.4, basedupon subsequent subdivisi
34、on of the sample into sub-sets for conditioning and testing. Specimen size shall be selected to encompassthe direct measurement region of the meter/electrode assembly with minimal excess material. Specimens must be free of visibleD4444 132irregularities such as knots, decay, reaction wood, and resin
35、 concentrations. The specimens shall be conditioned at 25 6 1C andselected relative humidities to each of five EMC levels between 7 and 21 % (see Guide D4933). Alternatively, specimens may beequilibrated (following a desorption path) at each of the five EMC conditions.6.2.3.1 SpeciesSpecies shall be
36、 identified. If the sample represents a species group, the individual species of each specimenshall be identified if anatomically possible.6.2.3.2 Sapwood/HeartwoodSpecimens shall be chosen to be entirely sapwood or heartwood, or two separate groups of each,but not mixed in the same specimens. It sh
37、all be reported if sapwood/heartwood mixing is unavoidable.6.2.3.3 Wood CharacteristicsSpecimen selection for wood characteristics shall be considered in setting sample size.6.2.4 TestingThere are two steps in the testing phase of calibration. The first is meter measurements on the wood samplesfollo
38、wing the procedures of this test method and the applicable criteria provided by the manufacturer. The second step isconducting a direct moisture content determination following Test Methods D4442.6.2.4.1 Meter MeasurementThe equilibrated specimens are numbered, weighed, and a meter measurement taken
39、 with theelectrode aligned on the specimen in accordance with the manufacturers recommendation. The speed of response of the meter willdetermine the timing of the meter reading; manufacturers recommendations shall be followed unless this variable is examined aspart of the calibration process.6.2.4.2
40、 Direct Moisture TestThe MC of each specimen shall be determined by the appropriate direct method (Test MethodsD4442) after the meter measurement. Procedures shall be followed to prevent moisture gain or loss from the specimens betweenthe meter measurement and the direct test.6.2.5 Correction Factor
41、 DeterminationThe corrections applied to moisture meters and the precision and bias of the metersmay differ significantly between the technology employed and manufacturing variables. Wood characteristics, species, temperatureand chemical additives are specimen variables that may require correction f
42、actors. The following procedures shall be followed todetermine correction factors for meters.6.2.5.1 Correction for Wood Sample CharacteristicsThe moisture meter scale readings determined from 6.2.4.1 proceduresshall be related to the corresponding MC from 6.2.4.2 for each specimen in the sample by
43、regression or analysis of varianceanalysis.(1) Species calibrations that are intended to represent an entire species (for example, to correspond to globally-determineddesign values assigned to structural products) shall be obtained only by conducting species-wide sampling.(2) The species sampling su
44、ggested in this test method is not required to be species-wide. Species representation claims basedon less-than species-wide sampling shall be correspondingly limited.6.2.5.2 Correction for Wood Sample TemperatureThis correction shall be applied after the meter has been standardized inaccordance wit
45、h Section 5 and calibrated in accordance with 6.2.5.1. The options for this correction are to use a standardtemperature correction or to conduct a laboratory calibration.(1) Determination of Temperature CorrectionThe correction shall be based on samples prepared as specified in 6.2.2 exceptthat spec
46、imens of known MC (Guide D4933) at 25 6 1C (77 6 1.8F) shall be placed, with electrodes and temperature probesattached, in a sealed container. The change in indicated MC (meter indication) shall be recorded while changing temperaturethrough the desired range. A final meter reading must be made at 25
47、 6 1C (77 6 1.8F) to confirm that the MC has not variedfrom the temperature cycling.(2) Standard Temperature CorrectionIf a laboratory determination is not made for conductance meters, the followingrelationship shall be used to correct MC below the fiber saturation point over the temperature range o
48、f 0 to 40C.MC25MC110.06MC10.5!T2225! (1)where:MC1 = the MC at 25C.This information is presented in Appendix X2.6.2.5.3 Correction for Chemical AdditivesMeter assemblies applied to wood materials that have been treated with additivesand have adhesives interspersed with the fiber, or both, shall be ca
49、librated with those materials following the precepts of this andprevious sections on sampling and preparation. Some discretion is appropriate on temperature and moisture levels, depending onthe end use of the products.6.2.6 ReportThe following wood sample information shall be recorded: MC, size (dimensions in each plane), species andmethod of species identification, sapwood/heartwood percentage, density or specific gravity, growth rate (rings/25 mm) and ringorientation, and earlywood/latewood percentage. For other materials, the appropriate wood
