1、Designation: D6782 05D6782 13Standard Test Methods forStandardization and Calibration of In-Line Dry LumberMoisture Meters1This standard is issued under the fixed designation D6782; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, t
2、he 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.1. Scope1.1 These test methods apply to instruments designed to detect, or measure, moisture in wood which has been dri
3、ed below thefiber saturation point. The purpose of these tests is to provide a unified standard against which such systems can demonstrate theirsuitability for their intended use (see Appendix X1).1.1.1 Sensitivity to thin layers of surface moisture such as caused by dew or brief rain exposure is no
4、t addressed by thesemethods. Applications, such as screening material for surface adhesion, may require additional assessment methodology andcriteria (see Appendix X5).1.2 The standard is configured to support tests by moisture meter manufacturers as well as end-users of such systems, thereforethe t
5、ext follows two tracks (see Appendix X2).1.3 Test methods specified for manufacturers are generally designed for laboratory settings and are intended to provide astandard against which a manufacturer certifies calibration and general system conformance.1.4 Test methods for end-users are generally de
6、signed for field settings and are intended as a standardized set of procedures fordetermining the suitability of a specific machine for a particular use.1.5 Applications such as lumber marking or sorting systems utilizing the output of the in-line meter are not part of this standard.1.6 Applications
7、 requiring sensitivity to and identification of localized wet areas are limited to general recommendations. Thepresence of wet-spots is the subject of Appendix X8.1.7 The values stated in SI units are to be regarded as the standard. The values given in parentheses are for information only.1.8 This s
8、tandard 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 prior to use.2. Referenced Documents2.1
9、ASTM Standards:2D1990 Practice for EstablishingAllowable Properties for Visually-Graded Dimension Lumber from In-Grade Tests of Full-SizeSpecimensD2395 Test Methods for Specific Gravity of Wood and Wood-Based MaterialsD2915 Practice for Sampling and Data-Analysis for Structural Wood and Wood-Based P
10、roductsD4442 Test Methods for Direct Moisture Content Measurement of Wood and Wood-Base MaterialsD4444 Test Method for Laboratory Standardization and Calibration of Hand-Held Moisture MetersD4933 Guide for Moisture Conditioning of Wood and Wood-Based MaterialsD5536 Practice for Sampling Forest Trees
11、 for Determination of Clear Wood Properties3. Terminology3.1 Definitions of Terms Specific to This Standard:1 These test methods are under the jurisdiction ofASTM Committee D07 on Wood and are the direct responsibility of Subcommittee D07.01 on Fundamental Test Methodsand Properties.Current edition
12、approved Oct. 1, 2005April 1, 2013. Published October 2005May 2013. Originally approved in 2002. Last previous edition approved in 20042005 asD6782 - 04.D6782 - 05. DOI: 10.1520/D6782-05.10.1520/D6782-13.2 For referencedASTM standards, visit theASTM website, www.astm.org, or contactASTM Customer Ser
13、vice 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 standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previo
14、us version. Becauseit 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 versionof the standard as published by ASTM is to be considered the official document.Copyright ASTM Inte
15、rnational, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States13.1.1 accept/reject meters, nmeters that permit identification or sorting, or both, of pieces into moisture content classes. Thesimplest design has one set point or target level to separate wetter from dri
16、er pieces. Often the meters described in 3.1.5 may beoperated as accept/reject meters.3.1.2 field, nan environment usually not meeting the criteria of 3.1.4. This is often a meter installation at the wood processingfacility where the meter and the lumber are subject to the process environment of mil
17、l production.3.1.3 flow, na term that describes the movement and orientation of the piece with respect to the sensing area.3.1.3.1 longitudinal-flowin this flow arrangement, pieces pass lengthwise through the sensing area.All or some portion of thelength may be sensed.3.1.3.2 transverse-flowin this
18、flow arrangement, the pieces pass crosswise through the sensing area. Transverse metersfrequently have more than one sensing area, consequently, the meter may sense more than one area of the piece even if the entirepiece is not sensed.3.1.4 laboratory, nan environment under which conditions of tempe
19、rature and moisture content can be controlled withinstated tolerances and which permit use of carefully selected and controlled specimens.3.1.5 meters, nin-line (or in process) moisture sensors designed to respond in one pass to the moisture content of a piecepassing the sensing area.3.1.5.1 Discuss
20、ionMeters are typically a system consisting of one or more fixed sensing areas (termed heads) and a processing/readout console thatmay be remote from the region where sensing takes place. Meters may be either non-contact or contact types, and are considerednondestructive if the anticipated performan
21、ce of the product is not adversely affected by the meter. The magnitude of the sensingarea (sampling area) is often regarded in processing as representative of the entire piece, although the intended productrequirements may require alternate sampling or analysis schemes. The term sensing region is s
22、ometimes used in lieu of sensingarea to encompass the three-dimensional sensing pattern of a meter. Meters may have more than one sensing area; consequently,the meter may independently sense more than one area of the piece. Meters may be designed to indicate moisture contentpercentage, to operate as
23、 accept/reject instruments, or to be used for both applications.3.1.6 moisture content level, nthe moisture content at which products are defined as dry, or at which accept/reject decisionsare made. This level is dependent upon the specific grading rule, quality control requirements or product speci
24、fication.3.1.7 moisture indicators, nmeters which display or record the estimated moisture content, or both. The moisture content isestimated from a predetermined relationship between the meter output and moisture content determined by a standard method.3.1.7.1 DiscussionTypical sensing principles a
25、re given in Appendix X3.3.1.8 Standardization and Calibration:Calibration:3.1.8.1 standardizationthe determination of the response of the meter to a reference material (see Appendix X4).3.1.8.2 calibrationthe determination of the relationship between the response of a standardized meter and the mois
26、ture contentof a reference material, determined by a standard method (see Appendix X4).3.1.9 test modes, nthese terms describe the status of the piece during measurement.3.1.9.1 staticthe piece is stationary in the sensing area when the moisture measurement is made.3.1.9.2 dynamicthe piece moves thr
27、ough the sensing area during measurement.3.1.10 wet-spots, nlocalized area of moisture content higher than adjacent wood, most commonly caused by infected wood,localized obstructions to uniform drying or non-uniform drying characteristics of the wood (see Appendix X8).4. Significance and Use4.1 In-l
28、ine meters provide a rapid means of detecting moisture content of lumber or wood products in processing (that is, ona continuous production line). Two major uses are monitoring the performance of the drying process (air drying, kiln drying), andproviding sorting or identification of material at pred
29、etermined levels of moisture content. These measurements are inferential inthe sense that physical measurements are made and compared against calibration curves to obtain an indirect measure of moisturecontent. These measurements may be influenced by one or more physical properties such as actual mo
30、isture content (average andgradient; see Appendix X5), density, surface moisture, chemical composition, size, and temperature of wood. In addition, themeasurements may also be influenced by environmental conditions and the design specifications of the meter. The bestperformance is obtained by an awa
31、reness of the effect of each parameter on the meter output and correction of readings as specifiedby these test methods.D6782 1324.2 The two major anticipated users of these test methods are instrument manufacturers whose primary concern is laboratorystandardization and calibration, and instrument o
32、wners who may have a primary focus on field standardization and calibration.These test methods present the laboratory and the field as separate tracks (see Appendix X2).4.2.1 Laboratory Standardization and CalibrationThis portion of these test methods is intended for guidance of equipmentmanufacture
33、rs. Specific test recommendations are tailored to the capabilities of a laboratory environment.4.2.2 Field Standardization and CalibrationThe predominant use of in-line meters is in production in which lumbercharacteristics and environmental conditions reflect actual mill processes. Field standardiz
34、ation and calibration is essential toaddress or encompass much of the variability in production.4.2.3 Applications using the output of the in-line moisture meter may modify the meter output signals or have inherent responsecharacteristics that are not representative of the meter.5. Laboratory Standa
35、rdization and CalibrationThis procedure is intended for testing of a specific model or version of meters.5.1 Laboratory StandardizationStandardization shall be performed on the meter to test the integrity of the meter and sensingregion. The meter shall be standardized using suitable reference materi
36、als to provide at least one reference point other than zeroon the meter readout. In transverse feed systems, standardization shall be performed separately for each sensing region.5.1.1 Reference SpecimensThese references are often recommended or provided, or both, by the manufacturer of the meter.In
37、 absence of recommended reference specimens, materials shall be obtained that will provide consistent results during testing andretesting.NOTE 1Although the references are preferably non-hygroscopic, they maybe hygroscopic if due care is used to assure consistency during testing. Forexample, uniform
38、ly equalized clear wood specimens could be used if stored to maintain constant moisture content.5.1.2 Test ProcedureIn the following procedure, at least one reference specimen shall be used. Before each test, the meter shallbe initialized by adjusting to the manufacturers recommended initial reading
39、 with no material in the sensing region. The static anddynamic tests are to be conducted at room temperature (20-30C/68-86F). Any deviation from this temperature shall bedocumented in the report.5.1.2.1 PositioningThe reference materials shall be positioned in the sensing region as recommended by th
40、e manufacturer andconsistent with the constraints of the intended or recommended installation (see Appendix X6).NOTE 2Although the procedure specifies a single position, it may be useful to vary the position systematically to assess positional sensitivity. Thevariation in position may provide inform
41、ation on requirements for installation accuracy and effects from board misalignment, such as skewing or warping.5.1.2.2 Static Standardization TestAfter initializing, conduct a static standardization by placing the reference material in thesensing zone with the feed system disabled.5.1.2.3 Dynamic S
42、tandardization TestAfter initializing and conducting the static standardization (5.1.2), sequentially placeeach reference specimen (See 5.1.1 and Note 3) on a feed assembly outside the sensing zone. Energize the feed assembly to movethe reference through the sensing zone at a selected constant speed
43、. The speed selected shall be consistent with the intendedinstallation. Record the meter reading (for example, maximum or average) as the reference standard passes through the sensingzone. Repeat the test at the selected test speeds. (The more detailed procedure of the dynamic test is described in A
44、ppendix X7).NOTE 3In some systems, such as longitudinal flow meters operating at high speed, it may not be possible to conduct dynamic laboratorystandardization at operating speeds for practical reasons of control and safety. In these situations, the static or slow speed standardization results will
45、necessarily be the basis for proceeding to the calibration step.5.1.2.4 Temperature TestThe test shall be conducted at -20C, 0C, 20C, 40C and 60C (-4F, 32F, 68F, 104F and 140F)to determine the response of reference material, sensing heads, and console with temperature.At each temperature level, the
46、systemcomponents shall be at specified thermal equilibrium, allowing sufficient time for any temperature soak effect. Record the observedtemperature and meter reading at each temperature level.(1) Reference MaterialWith the sensing heads and console at ambient room temperature (20-30C/68-86F), condi
47、tion thereference material at the temperatures listed in 5.1.2.4. Quickly insert the reference material within the electrical field of onesensing head. Repeat the measurement at each temperature level and record average readings.(2) Sensing HeadsWith the console at ambient room temperature (20-30C/6
48、8-86F), place the sensing heads in a room tocycle to temperatures listed in 5.1.2.4.Allow the reference specimen to remain with the sensing heads. Determine the thermal driftof each sensing head by the difference of readings from those obtained in (1).(3) ConsoleWith the sensing heads and reference
49、material at ambient room temperature (20-30C/68-86F), cycle the consolethrough the temperatures listed in 5.1.2.4. Determine the thermal drift of the console by differences in readings from those obtainedin (1) and (2).5.1.3 ReportThe report shall include the data collected in 5.1.2 together with a detailed description of the reference materials,the method used for temperature exposure, and any variation from the specified procedure.5.2 Laboratory Calibration (MC Indicators)This method is intended for obtaining the greatest accur
