1、Designation: E1629 07 E1629 12Standard Practice forDetermining the Impedance of Absolute Eddy-CurrentProbes1This standard is issued under the fixed designation E1629; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last
2、 revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope Scope*1.1 This practice covers a procedure for determining the impedance of absolute eddy-current probes (bridge-type, air or
3、 ferritecore, wire wound, shielded, or unshielded) used for finding material defects in electrically conducting material. This practice isintended to establish a uniform test methodology to measure the impedance of eddy-current probes prior to receipt of these probesby the purchaser or the specifier
4、.1.2 LimitationsThis practice does not address the characterization or measurement of the impedance of differential, a-ccoupled, or transmit/receive types of probes. This practice does not address the use of magnetic materials in testingexaminationprobes. This practice shall not be used as a basis f
5、or selection of the best probe for a particular application or as a means by whichto calibrate or standardize a probe for a specific examination. This practice does not address differences in the impedance valuesthat can be obtained when the probe and material are in relative motion, as in a rotatin
6、g probe, since the procedure described hererequires the probe and material to be stationary.1.3 UnitsThe values stated in SI units are to be regarded as the standard. The values given in parentheses are for informationonly. mathematical conversions to inch-pound units that are provided for informati
7、on only and are not considered standard.1.4 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 regulatoryli
8、mitations prior to use.2. Referenced Documents2.1 The following document forms a part of this practice to the extent specified herein:2.2 ASTM Standards:E1316 Terminology for Nondestructive Examinations23. Terminology3.1 DefinitionsThe terminology relating to eddy-current examination that appears in
9、 Terminology E1316 shall apply to theterms used in this practice.3.1 DefinitionsDefinitions of terms relating to electromagnetic examination are given in Terminology E1316.3.2 Definitions of Terms Specific to This Standard:3.2.1 eddy-current test blockreference standard for the purposes of the metho
10、d described in this practice, a rectangularblock made of an aluminum alloy (see 6.1.2) to which an active eddy-current probe is applied. The eddy-current reference standardcan also be referred to as an eddy-current test block.3.3 Mathematical Symbols:3.3.1 ja symbol used in electrical engineering to
11、 represent =21 . It is associated with the restriction to the flow of electricalcurrent caused by capacitors and coils.3.3.2 N any number.1 This practice is under the jurisdiction of ASTM Committee E07 on Nondestructive Testing and is the direct responsibility of Subcommittee E07.07 on Electromagnet
12、icMethod.Current edition approved July 1, 2007Nov. 1, 2012. Published July 2007November 2012. Originally approved in 1994. Last previous edition approved in 20012007 asE1629 - 94E1629 - 07.(2001). DOI: 10.1520/E1629-07.10.1520/E1629-12.2 For referenced ASTM standards, visit the ASTM website, www.ast
13、m.org, or contact ASTM 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 standard and is intended only to provide the user of an ASTM standard an indication of what c
14、hanges 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 cases only the current versionof the standard as published by ASTM is to be considered the of
15、ficial document.*A Summary of Changes section appears at the end of this standardCopyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States13.3.3 | N|the magnitude of N, regardless whether N is positive, negative, or a vector quantity.3.3.4 =N t
16、he square root of N.3.3.5 (N)2N squared, that is, N N.3.3.6 N delta N, the change or difference in N.3.4 Abbreviations:3.4.1 tanused for the tangent function. The tan1, arc tangent or inverse tangent function, returns a value that is a measureof an angle and can be in either degrees or radians. When
17、 using a calculator to determine the tan1, care should be taken todetermine whether the answer is in degrees or radians since the numerical values that represent the same angle are different.3.4.2 cosused for the cosine function.3.4.3 sinused for the sine function.4. Significance and Use4.1 Eddy-cur
18、rent probes may be used for the nondestructive examination of parts or structures made of electrically conductingmaterials. Many of these examinations are intended to discover material defects, such as cracks, that may cause the part or structureto be unsafe or unfit for service. Eddy-current probes
19、 that fail to meet the performance level requirements of this practice shall notbe used for the examination of material or hardware unless the probe is qualified by some other system or an agreement has beenreached by the probe manufacturer and the purchaser, or both.5. General Practice5.1 Use of Te
20、st BlocksEddy-Current Reference StandardsThe test blocks eddy-current reference standards described in thispractice shall not be used for purposes other than measuring the impedance of eddy-current probes as specified in this practice.They shall not be used for standardizing an examination or for de
21、termining sensitivity to flaws.5.2 ResponsibilityInitial determination of the impedance values of eddy-current probes shall be performed by the probemanufacturer in accordance with this practice. The results shall be delivered with the probe and maintained by the organizationusing the probe. The res
22、ults should include a description of the measurement configuration and impedance values as listed in X1.4.While the retesting of probes may be performed using this practice, only the results obtained before the probe is in use should becompared to the initial impedance values. The impedance results
23、should not be compared to the initial values after a probe has beenused.6. Specific Practice6.1 Test MethodImpedance measurements shall be made on an aluminum alloy testreference block with a machined slot thatconforms to the requirements of this practice. The operating frequency (as specified by th
24、e probe manufacturer) may vary for eachprobe examined, depending on the specific probe geometry, required skin depth, matching impedance, desired signal strength, andapplication. A commercial impedance measuring instrument that conforms to 6.1.1 shall be used to make the measurements. Themeasurement
25、s will be recorded on the worksheet (Appendix X1) to calculate the probe impedance. The calculated values shall becompared to the acceptable criteria (6.3) to determine probe acceptability.6.1.1 Test EquipmentThe test instrument shall be either a commercial impedance measuring instrument or an LCR m
26、eter withan oscillator capable of driving a current in the probe at the probes operating frequency. The output shall display the probeimpedance in either polar coordinates, providing a magnitude and a phase angle, or rectangular coordinates, providing resistive andreactive components of the impedanc
27、e, or both formats, that is, in polar and rectangular coordinates. This instrument shall becertified as having been calibrated in accordance with the manufacturers specifications, with the calibration sticker indicating thecalibration date and the required interval or next calibration date.6.1.2 Tes
28、t BlocksReference StandardsThe test blockreference standard shall be fabricated from 7075-T6 aluminum alloy1.9-cm (0.75-in.) thick, with slotted holes for testing bolt hole probes and a slotted flat section for testing surface probes. All testsurfaces surfaces of the reference standard shall be poli
29、shed to an average finish 15 m (591 in.). The conductivity of thealuminum alloy should be between 30 and 35 % IACS.6.1.2.1 The slotted flat section shall have side measurements of at least six times the coil diameter or 5.1 by 5.1 cm (2 by 2 in.),whichever is larger. The slot shall be machined acros
30、s the blocks surface and shall measure at least 5.0 cm (2-in.) long. The slotcross section shall measure 0.1 6 0.01 mm (0.004 6 0.0004 in.) wide and 0.5 6 0.025 mm (0.02 6 0.001 in.) deep.6.1.2.2 The test holes shall be made for all of the nominal sizes of bolt hole probes to be examined. The edges
31、of the holes shallbe spaced 1.9-cm (0.75-in.) apart from each other and from the block reference standard edges. The slot shall run the entire lengthof the hole and will be 0.1 6 0.01-mm (0.004 6 0.0004-in.) wide and 0.5 6 0.025-mm (0.02 6 0.001-in.) deep.6.1.2.3 Fig. 1 shows a representative test b
32、lockreference standard with the holes used for testing two different sizes of bolt holeprobes. The length of the block (x + 5.1 cm) depends on the number and size of the test holes required by the user, as well as theamount of clearance required between each hole and the blocks reference standards e
33、dges.6.2 Measurement Procedure:E1629 1226.2.1 MeasurementsImpedance values can be expressed in different ways. Impedances are most commonly given in eitherrectangular or polar coordinates. In polar form, the impedance is expressed as a magnitude, |Z|, with a corresponding phase angle, and often appe
34、ars as |Z| / . In rectangular form the impedance is expressed as a combination of a resistive component, R, anda reactive or imaginary (denoted by j) component, X. This form often appears as R 6 jX.Fig. 2 shows two points measured in bothforms and the resulting impedance change (Z) calculation. This
35、 is typical of the way in which impedance changes are measuredon actual eddy-current probes using the test method approach specified in this practice. The impedance of a probe is measured firstoff the slot and then on the slot in this method, and the difference between these two measurements is calc
36、ulated. An error mayoccur in the calculations if appropriate coordinate conversions are not made (addition and subtraction are performed in the caseof rectangular coordinates and multiplication and division in the case of polar coordinates).6.2.1.1 All performance tests shall be conducted within the
37、 temperature range from 15 to 27C (60 to 80F). The probe testfrequency shall depend on the rated operating frequency of the particular probe under test (see X1.4.3.3).6.2.2 Probe Impedance in AirAttach the probe to the impedance measuring instrument, and position the probe at least 50.8mm (2 in.) aw
38、ay from any electrically conducting material or hardware, or both. Measure the impedance and record the impedancevalues on the worksheet. Compare the measurement to the values listed in 6.3.1.6.2.3 Average Off-Slot Probe Impedance Place the probe on the surface of or in the hole in the test block,re
39、ference standard,as appropriate. For a surface probe, place the probe on four different positions on the face of the block. reference standard. Thecenter of each position shall be at least four coil diameters from any edge, slot, or hole. For a bolt hole probe, rotate the probe facein the hole to fo
40、ur different positions that are away from the slot and the top and bottom of the hole. Measure the impedance andrecord the four impedance values on the worksheet in either polar or rectangular coordinates. If necessary, convert the polar valuesto Roff and Xoff (resistive and reactive components). Ca
41、lculate the magnitude of each of the measurements and record them on theworksheet. Determine the variation (scatter) in the magnitudes of the measurements as defined in X1.3.1.3 and compare it to therequirements given in 6.3.2. When acceptable values are obtained, average the four values to calculat
42、e Roff avg and Xoff avg. Recordthe averages on the worksheet.6.2.4 Maximum On-Slot ImpedancePosition the probe face on the slot to obtain a maximum impedance reading. Perform thisprocedure four times, and record the four resulting impedances in rectangular coordinates, Ron and Xon, on the worksheet.
43、 Averagethe four values to calculate Ron avg and Xon avg. Record the averages on the worksheet.6.2.5 Probe Performance CriterionThe probe impedance change caused by the slot, Z, is the magnitude of Ron avg Roff avgand Xon avg Xoff avg . The fractional change is the absolute value of Z divided by |Zo
44、ff avg|. Appendix X1 contains the formulasfor calculating the values of |Z| and| Zoff avg|. Record the calculated values on the worksheet and compare them to the requirementsof 6.3.3 to determine acceptance.FIG. 1 Representative Test BlockEddy-Current Reference StandardFIG. 2 Rectangular and Polar C
45、oordinates and Resulting ZE1629 1236.3 Acceptance CriteriaAcceptance of a probe being characterized by this practice requires that it meet all of the followingcriteria:6.3.1 Probe Impedance in AirUnless otherwise specified, the magnitude of the probe impedance in air shall be between 20and 1000 , an
46、d the phase shall be between 70 and 90 deg. An impedance value below 20 indicates the possibility of a shortcircuit in the probe coil, and a value above 1000 indicates a possible open circuit.6.3.1.1 The magnitude of the impedance in air shall be within 10 % of the value specified for that type of p
47、robe by the probemanufacturer and be within the input impedance range specified for the measuring instrument.6.3.2 Measurement ScatterA variation greater than 4 % among the off-slot impedance measurements indicates that the valuesare too scattered. The measurements must be repeated using greater car
48、e in holding the surface probe more securely or fitting thebolt hole probe more snugly in the hole. Repeated high variation indicates that an analysis of the system should be performed usingdifferent examiners or known acceptable probes. The probe is unacceptable if the measurement scatter cannot be
49、 reduced to theacceptable value.6.3.3 Probe Impedance RatioThese ratios will be determined by agreement between the eddy-current probe manufacturer andthe probe purchaser.7. Keywords7.1 absolute eddy-current probes; eddy-current probes; impedance; nondestructive testingAPPENDIXES(Nonmandatory Information)X1. WORKSHEET FOR CALCULATION OF RESULTSX1.1 GeneralX1.1.1 ScopeThis appendix provides mathematical formulas and a worksheet for recording measurements and calculatingresults. It is recommended that a blank worksh
