ASTM_D_4166_-_99.pdf

Designation:D 4166 99An American National StandardStandard Test Method forMeasurement of Thickness of Nonmagnetic Materials byMeans of a Digital Magnetic Intensity Instrument1This standard is issued under the fixed designation D 4166;the number immediately following the designation indicates the year oforiginal adoption or,in the case of revision,the year 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.Scope*1.1 This test method covers the measurement of thickness ofany nonmagnetic material by means of a digital magneticintensity instrument.1.2 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 appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.1.3 There is no similar or equivalent ISO standard.2.Summary of Test Method2.1 In this test method,a magnetic sensing device iscalibrated and placed on one side of the material to bemeasured.A magnet of known intensity is placed on theopposite side and the distance between the magnet and themagnetic sensing device shows as a digit that can be convertedto inch-pound or metric units by reference to a table.3.Significance and Use3.1 This test method is useful for measuring the wallthickness of plastic vessels and other plastic structures wherethe geometry of the equipment does not permit direct measure-ment by conventional methods,such as micrometers,calipers,and rulers.This test method is not limited to plastics and can beused for all nonmagnetic materials.It provides for a rapid andaccurate thickness measurement,without the need for drillingand repair of holes.3.2 Accuracies are not affected by density variations,per-mitting the measurement of composites made up of a variety ofmaterials of varying densities.By placement of the magneticsource on the mold surface,thickness measurements can bemade during and after fabrication of plastic products to verifythickness and adherence to specifications.4.Interferences4.1 Any instrument measuring the intensity of a magneticfield can sometimes be influenced by a strong artificial ornatural magnetic field.4.2 Any magnetic material located in the space between themagnet and the sensor will distort the measurement.4.3 A major temperature change(+10F,+5.6C)will causea slight drift in calibration,requiring a recalibration at the newtemperature prior to making the measurement.5.Apparatus5.1 Micro Digital Magnetic Thickness Sensor.26.Sampling6.1 Two separate measurements at each location shall betaken.If a variation in excess of 0.01 in.(0.25 mm)appears,athird measurement shall be taken.7.Procedure7.1 CalibrationCalibrate the magnetic sensing device asfollows:7.1.1 Center the magnet supplied with the apparatus on theend of the sensor head and depress the“set button.Thisestablishes the zero measurement point.7.2 Measurement:7.2.1 Place the magnet used in the calibration procedure(7.1)on one side of the material to be measured.7.2.2 Place the magnetic sensing device on the opposite sideand move it in a criss-cross motion until the digit reaches itslowest point.This denotes that the magnetic sensing device iscentered on the magnet.7.2.3 Depress the“set button to lock in the measurementshown in the digital read-out.7.2.4 To perform further measurements,repeat 7.1.1-7.2.3.1This test method is under the jurisdiction ofASTM Committee D-20 on Plasticsand is the direct responsibility of Subcommittee D20.23 on Reinforced PlasticPiping Systems and Chemical Equipment.Current edition approved July 10,1999.Published September 1999.Originallypublished as D 4166 82.Last previous edition D 4166 94.2The Polygauge Micro Digital Magnetic Thickness Sensor,manufactured byPolygauge,188 Wilkinson Rd.,Unit 9,Brampton,Ontario Canada L 6T 4W9,or itsequivalent has been found satisfactory for this purpose.1*A Summary of Changes section appears at the end of this standard.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959,United States.8.Report8.1 Report the following information:8.1.1 Identification of the material or item measured,8.1.2 Exact location where measurement was made,8.1.3 Condition of two surfaces of material measured,8.1.4 Number of readings taken,and8.1.5 Date of inspection.9.Precision and Bias9.1 In October 1981,an interlaboratory evaluation wasconducted in an ASTM workshop.Persons interested in ob-taining a copy of the research report of this evaluation maycontact ASTM directly.39.1.1 In the workshop,80 measurements were taken using 4separate instruments,4 samples of varying thicknesses,and 8individuals.The average error experienced was 0.0062 in.(0.157 mm).10.Keywords10.1 plastic measurement;thickness measurementSUMMARY OF CHANGESThis section identifies the location of selected changes to this test method.For