1、Designation:C178914Standard Test Method forCalibration of Hand-Held Moisture Meters on GypsumPanels1This standard is issued under the fixed designation C1789;the number immediately following the designation indicates the year oforiginal adoption or,in the case of revision,the year of last revision.A
2、 number in parentheses indicates the year of last reapproval.Asuperscript epsilon()indicates an editorial change since the last revision or reapproval.1.Scope1.1 This test method applies to the calibration of handheldmoisture meters for gypsum board,glass faced gypsum panelsand fiber-reinforced gyps
3、um panels by means of electricalconductance and dielectric meters.The test uses wetted testspecimens which are dried down in at least 5 steps to determinethe moisture content based on the weight loss in comparison tothe dry weight.The test also supplies the ERH values for eachof the drying steps.1.2
4、 This test method has not been evaluated for the influ-ence of paint or wall covering materials on the indicatedmoisture content of a gypsum board or panel substrate.1.3 This standard does not purport to address all of thesafety concerns,if any,associated with its use.It is theresponsibility of the
5、user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2.Referenced Documents2.1 ASTM Standards:2C473 Test Methods for Physical Testing of Gypsum PanelProductsC1177 Specification for Glass Mat Gypsum Substra
6、te forUse as SheathingC1178 Specification for Coated Glass Mat Water-ResistantGypsum Backing PanelC1278 Specification for Fiber-Reinforced Gypsum PanelC1396 Specification for Gypsum BoardD4442 Test Methods for Direct Moisture Content Measure-ment of Wood and Wood-Base MaterialsD4444 Test Method for
7、Laboratory Standardization andCalibration of Hand-Held Moisture Meters2.2 ASHRAE Standard:32009 ASHRAE Handbook Fundamentals,Chapter 1 Psychrometrics,American Society of Heating,Refrigerat-ing and Air-conditioning Engineers3.Terminology3.1 Definitions of Terms Specific to This Standard:3.1.1 absolut
8、e humidity,dv,nthe ratio of the mass of watervapor to the total volume of the moist air sample.3.1.2 admittance,ninverse of impedance,a measure ofhow easily an electric current can flow through a material.3.1.3 conductance meters,nconductance meters are thosethat measure predominantly ionic conducta
9、nce between pointsof applied voltage,usually dc.3.1.3.1 DiscussionConductance meters generally havepins that penetrate into the material being measured.Direct-current conductance meters are commonly referred to asresistance meters.Most commercial conductance meters arehigh-input impedance(about 1012
10、),wide-range(104to 1012)ohmmeters.Their scales are generally calibrated to readdirectly in moisture content(oven-dry mass basis)for aparticular calibration material and at a specific referencetemperature.3.1.4 dew-point temperature,td,nthe temperature atwhich a sample of moist air being cooled at co
11、nstant pressureand moisture content reaches 100 percent relative humidity.3.1.4.1 DiscussionThe dew-point temperature is the tem-perature at which water condensation begins to occur on acooled surface in contact with moist air.3.1.5 dielectric meters,nmeters that measure primarily byadmittance or po
12、wer loss.3.1.5.1 DiscussionDielectric meters generally do not havepins that penetrate into the material being measured.There aretwo general types of dielectric meters that may be arbitrarilycategorized by their predominant mode of response admit-tance(or capacitance)and power loss.Both have surfacec
13、ontact electrodes and readout scales that are usually marked in1This test method is under the jurisdiction ofASTM Committee C11 on Gypsumand Related Building Materials and Systems and is the direct responsibility ofSubcommittee C11.01 on Specifications and Test Methods for Gypsum Products.Current ed
14、ition approved June 1,2014.Published July 2014.Originally approvedin 2013.Last previous edition approved in 2013 as C1789 13.DOI:10.1520/C1789-14.2For referenced ASTM standards,visit the ASTM website,www.astm.org,orcontact ASTM Customer Service at serviceastm.org.For Annual Book of ASTMStandards vol
15、ume information,refer to the standards Document Summary page onthe ASTM website.3Available from American Society of Heating,Refrigerating,and Air-Conditioning Engineers,Inc.(ASHRAE),1791 Tullie Circle,NE,Atlanta,GA30329,http:/www.ashrae.org.Copyright ASTM International,100 Barr Harbor Drive,PO Box C
16、700,West Conshohocken,PA 19428-2959.United States1 arbitrary units.Most dielectric meters operate in the r-ffrequency range,generally between 1 and 10 MHz.Admittancemeters respond primarily to the capacitance(dielectric con-stant)of the material being measured.Power loss meters reactprimarily to the resistance of the material.Readings of dielec-tric meters are significantly affected by the relative density(specific gravity)of the specimen material.3.1.6 equilibrium moisture content,EMC,nthe mois
