1、Designation: D 6782 05Standard Test Methods forStandardization and Calibration of In-Line Dry LumberMoisture Meters1This standard is issued under the fixed designation D 6782; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the yea
2、r of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.1. Scope1.1 These test methods apply to instruments designed todetect, or measure, moisture in wood which has been driedbelo
3、w the fiber saturation point. The purpose of these tests is toprovide a unified standard against which such systems candemonstrate their suitability for their intended use (see Appen-dix X1).1.2 The standard is configured to support tests by moisturemeter manufacturers as well as end-users of such s
4、ystems,therefore the text follows two tracks (see Appendix X2).1.3 Test methods specified for manufacturers are generallydesigned for laboratory settings and are intended to provide astandard against which a manufacturer certifies calibration andgeneral system conformance.1.4 Test methods for end-us
5、ers are generally designed forfield settings and are intended as a standardized set ofprocedures for determining the suitability of a specific machinefor a particular use.1.5 Applications such as lumber marking or sorting systemsutilizing the output of the in-line meter are not part of thisstandard.
6、1.6 The values stated in SI units are to be regarded as thestandard. The values given in parentheses are for informationonly.1.7 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to establish app
7、ro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2D 1990 Practice for Establishing Allowable Properties forVisually-Graded Dimension Lumber from In-Grade Testsof Full-Size SpecimensD 2395 Test Meth
8、ods for Specific Gravity of Wood andWood-Base MaterialsD 2915 Practice for Evaluating Allowable Properties forGrades of Structural LumberD 4442 Test Methods for Direct Moisture Content Measure-ment of Wood and Wood-Base MaterialsD 4444 Test Methods for Use and Calibration of Hand-HeldMoisture Meters
9、D 4933 Guide for Moisture Conditioning of Wood andWood-Base MaterialsD 5536 Practice for Sampling Forest Trees for Determina-tion of Clear Wood Properties3. Terminology3.1 Definitions of Terms Specific to This Standard:3.1.1 accept/reject meters, nmeters that permit identifica-tion or sorting, or bo
10、th, of pieces into moisture content classes.The simplest design has one set point or target level to separatewetter from drier pieces. Often the meters described in 3.1.5may be operated as accept/reject meters.3.1.2 field, nan environment usually not meeting thecriteria of 3.1.4. This is often a met
11、er installation at the woodprocessing facility where the meter and the lumber are subjectto the process environment of mill production.3.1.3 flow, na term that describes the movement andorientation of the piece with respect to the sensing area.3.1.3.1 longitudinal-flowin this flow arrangement, piece
12、spass lengthwise through the sensing area. All or some portionof the length may be sensed.3.1.3.2 transverse-flowin this flow arrangement, thepieces pass crosswise through the sensing area. Transversemeters frequently have more than one sensing area, conse-quently, the meter may sense more than one
13、area of the pieceeven if the entire piece is not sensed.3.1.4 laboratory, nan environment under which condi-tions of temperature and moisture content can be controlledwithin stated tolerances and which permit use of carefullyselected and controlled specimens.1These test methods are under the jurisdi
14、ction of ASTM Committee D07 onWood and are the direct responsibility of Subcommittee D07.01 on FundamentalTest Methods and Properties.Current edition approved Oct. 1, 2005. Published October 2005. Originallyapproved in 2002. Last previous edition approved in 2004 as D 6782 - 04.2For referenced ASTM
15、standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohock
16、en, PA 19428-2959, United States.3.1.5 meters, nin-line (or in process) moisture sensorsdesigned to respond in one pass to the moisture content of apiece passing the sensing area.3.1.5.1 DiscussionMeters are typically a system consist-ing of one or more fixed sensing areas (termed heads) and aproces
17、sing/readout console that may be remote from the regionwhere sensing takes place. Meters may be either non-contact orcontact types, and are considered nondestructive if the antici-pated performance of the product is not adversely affected bythe meter. The magnitude of the sensing area (sampling area
18、) isoften regarded in processing as representative of the entirepiece, although the intended product requirements may requirealternate sampling or analysis schemes. The term sensingregion is sometimes used in lieu of sensing area to encompassthe three-dimensional sensing pattern of a meter. Meters m
19、ayhave more than one sensing area; consequently, the meter mayindependently sense more than one area of the piece. Metersmay be designed to indicate moisture content percentage, tooperate as accept/reject instruments, or to be used for bothapplications.3.1.6 moisture content level, nthe moisture con
20、tent atwhich products are defined as dry, or at which accept/rejectdecisions are made. This level is dependent upon the specificgrading rule, quality control requirements or product specifi-cation.3.1.7 moisture indicators, nmeters which display orrecord the estimated moisture content, or both. The
21、moisturecontent is estimated from a predetermined relationship betweenthe meter output and moisture content determined by astandard method.3.1.7.1 DiscussionTypical sensing principles are given inAppendix X3.3.1.8 Standardization and Calibration:3.1.8.1 standardizationthe determination of the respon
22、seof the meter to a reference material (see Appendix X4).3.1.8.2 calibrationthe determination of the relationshipbetween the response of a standardized meter and the moisturecontent of a reference material, determined by a standardmethod (see Appendix X4).3.1.9 test modes, nthese terms describe the
23、status of thepiece during measurement.3.1.9.1 staticthe piece is stationary in the sensing areawhen the moisture measurement is made.3.1.9.2 dynamicthe piece moves through the sensing areaduring measurement.4. Significance and Use4.1 In-line meters provide a rapid means of detectingmoisture content
24、of lumber or wood products in processing(that is, on a continuous production line). Two major uses aremonitoring the performance of the drying process (air drying,kiln drying), and providing sorting or identification of materialat predetermined levels of moisture content. These measure-ments are inf
25、erential in the sense that physical measurementsare made and compared against calibration curves to obtain anindirect measure of moisture content. These measurementsmay be influenced by one or more physical properties such asactual moisture content (average and gradient; see AppendixX5), density, su
26、rface moisture, chemical composition, size, andtemperature of wood. In addition, the measurements may alsobe influenced by environmental conditions and the designspecifications of the meter. The best performance is obtainedby an awareness of the effect of each parameter on the meteroutput and correc
27、tion of readings as specified by these testmethods.4.2 The two major anticipated users of these test methodsare instrument manufacturers whose primary concern is labo-ratory standardization and calibration, and instrument ownerswho may have a primary focus on field standardization andcalibration. Th
28、ese test methods present the laboratory and thefield as separate tracks (see Appendix X2).4.2.1 Laboratory Standardization and CalibrationThisportion of these test methods is intended for guidance ofequipment manufacturers. Specific test recommendations aretailored to the capabilities of a laborator
29、y environment.4.2.2 Field Standardization and CalibrationThe predomi-nant use of in-line meters is in production in which lumbercharacteristics and environmental conditions reflect actual millprocesses. Field standardization and calibration is essential toaddress or encompass much of the variability
30、 in production.4.2.3 Applications using the output of the in-line moisturemeter may modify the meter output signals or have inherentresponse characteristics that are not representative of the meter.5. Laboratory Standardization and CalibrationThis procedure is intended for testing of a specific mode
31、l orversion of meters.5.1 Laboratory StandardizationStandardization shall beperformed on the meter to test the integrity of the meter andsensing region. The meter shall be standardized using suitablereference materials to provide at least one reference point otherthan zero on the meter readout. In t
32、ransverse feed systems,standardization shall be performed separately for each sensingregion.5.1.1 Reference SpecimensThese references are often rec-ommended or provided, or both, by the manufacturer of themeter. In absence of recommended reference specimens, ma-terials shall be obtained that will pr
33、ovide consistent resultsduring testing and retesting.NOTE 1Although the references are preferably non-hygroscopic, theymaybe hygroscopic if due care is used to assure consistency duringtesting. For example, uniformly equalized clear wood specimens could beused if stored to maintain constant moisture
34、 content.5.1.2 Test ProcedureIn the following procedure, at leastone reference specimen shall be used. Before each test, themeter shall be initialized by adjusting to the manufacturersrecommended initial reading with no material in the sensingregion. The static and dynamic tests are to be conducted
35、atroom temperature (20-30C/68-86F). Any deviation from thistemperature shall be documented in the report.5.1.2.1 PositioningThe reference materials shall be posi-tioned in the sensing region as recommended by the manufac-turer and consistent with the constraints of the intended orrecommended install
36、ation (see Appendix X6).NOTE 2Although the procedure specifies a single position, it may beuseful to vary the position systematically to assess positional sensitivity.The variation in position may provide information on requirements forD6782052installation accuracy and effects from board misalignmen
37、t, such asskewing or warping.5.1.2.2 Static Standardization TestAfter initializing, con-duct a static standardization by placing the reference materialin the sensing zone with the feed system disabled.5.1.2.3 Dynamic Standardization TestAfter initializingand conducting the static standardization (5.
38、1.2), sequentiallyplace each reference specimen (See 5.1.1 and Note 3) on a feedassembly outside the sensing zone. Energize the feed assemblyto move the reference through the sensing zone at a selectedconstant speed. The speed selected shall be consistent with theintended installation. Record the me
39、ter reading (for example,maximum or average) as the reference standard passes throughthe sensing zone. Repeat the test at the selected test speeds.(The more detailed procedure of the dynamic test is describedin Appendix X7).NOTE 3In some systems, such as longitudinal flow meters operatingat high spe
40、ed, it may not be possible to conduct dynamic laboratorystandardization at operating speeds for practical reasons of control andsafety. In these situations, the static or slow speed standardization resultswill necessarily be the basis for proceeding to the calibration step.5.1.2.4 Temperature TestTh
41、e test shall be conducted at-20C, 0C, 20C, 40C and 60C (-4F, 32F, 68F, 104F and140F) to determine the response of reference material, sensingheads, and console with temperature. At each temperaturelevel, the system components shall be at specified thermalequilibrium, allowing sufficient time for any
42、 temperature soakeffect. Record the observed temperature and meter reading ateach temperature level.(1) Reference MaterialWith the sensing heads and con-sole at ambient room temperature (20-30C/68-86F), condi-tion the reference material at the temperatures listed in 5.1.2.4.Quickly insert the refere
43、nce material within the electrical fieldof one sensing head. Repeat the measurement at each tempera-ture level and record average readings.(2) Sensing HeadsWith the console at ambient roomtemperature (20-30C/68-86F), place the sensing heads in aroom to cycle to temperatures listed in 5.1.2.4. Allow
44、thereference specimen to remain with the sensing heads. Deter-mine the thermal drift of each sensing head by the difference ofreadings from those obtained in (1).(3) ConsoleWith the sensing heads and reference materialat ambient room temperature (20-30C/68-86F), cycle theconsole through the temperat
45、ures listed in 5.1.2.4. Determinethe thermal drift of the console by differences in readings fromthose obtained in (1) and (2).5.1.3 ReportThe report shall include the data collected in5.1.2 together with a detailed description of the referencematerials, the method used for temperature exposure, and
46、 anyvariation from the specified procedure.5.2 Laboratory Calibration (MC Indicators)This methodis intended for obtaining the greatest accuracy by comparisonof the meter output to moisture content obtained gravimetri-cally using the oven-drying method (see Test MethodsD 4442). The accuracy of the de
47、sired results must be consistentwith the indicated accuracy of the specific oven-drying proce-dure in Test Methods D 4442. Laboratory calibration proce-dures are intended to provide reference data under controlledconditions of wood and ambient variables, This calibration isdesigned for full-scale ca
48、libration of the meter on actual woodspecimens having uniform moisture content (see 5.2.2). Metersmust be standardized (see 5.1) before being calibrated. Intransverse feed systems, calibration shall be done separatelyfor each sensing region. The calibration curve should neitherbe extrapolated below
49、the lowest nor above the highest valuetested.5.2.1 Calibration ObjectivesEstablish the objectives ofthe calibration test including specimen characteristics criteria(for example, uniformity of moisture content, density, species,and so forth), operating speed, and environmental conditions.5.2.2 Specimen Selection and PreparationSpecimensshall be selected to represent the characteristics identified ascalibration variables in 5.2.1. Other characteristics that are tobe held constant shall be identified as selection criteria. Oneexample is
