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ASTM A698/A698M-07

(Test Method)

Standard Test Method for Magnetic Shield Efficiency in Attenuating Alternating Magnetic Fields

Standard Test Method for Magnetic Shield Efficiency in Attenuating Alternating Magnetic Fields

SIGNIFICANCE AND USE
This test method provides an easy, accurate, and reproducible method for determination of shielding factors (attenuation ratios) in simple alternating magnetic fields.
Since the sensing or pickup coil is of finite size, the measured shielding factor tends to be the average value for the space enclosed by the coil. Due care is required when interpreting results when the coil is located near an opening in the shield.
This test method is suitable for design, specification acceptance, service evaluation, quality assurance, and research purposes on magnetic shields.
5.4 Provided geometrically identical shields are compared, this test method is also suitable for evaluation and grading of magnetic shielding materials.
SCOPE
1.1 This test method covers the means for determining the performance quality of a magnetic shield when placed in a magnetic field of alternating polarity.
1.2 This test method provides a means of evaluating and grading magnetic shielding materials to determine their suitability for use in the production of magnetic shields.
1.3 This test method shall be used in conjunction with and shall conform to the requirements of Practice A 34/A 34M.
1.4The values stated in either SI units or inch-pound units are to be regarded separately as standard. The values stated in each system may not be exact equivalents; therefore, each system shall be used independently of the other. Combining values from the two systems may result in non-conformance with the standard.
This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.

General Information

Status
Historical
Publication Date
30-Apr-2007
ICS
17.220.20 - Measurement of electrical and magnetic quantities
Technical Committee
A06 - Magnetic Properties
Drafting Committee
A06.01 - Test Methods
Current Stage
Ref Project

Relations

Replaces
ASTM A698/A698M-02 - Standard Test Method for Magnetic Shield Efficiency in Attenuating Alternating Magnetic Fields
Effective Date
01-May-2007
Replaced By
ASTM A698/A698M-15 - Standard Test Method for Magnetic Shield Efficiency in Attenuating Alternating Magnetic Fields
Effective Date
01-Apr-2015

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ASTM A698/A698M-07 - Standard Test Method for Magnetic Shield Efficiency in Attenuating Alternating Magnetic FieldsASTM A698/A698M-07 - Standard Test Method for Magnetic Shield Efficiency in Attenuating Alternating Magnetic Fields
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ASTM A698/A698M-07 - Standard Test Method for Magnetic Shield Efficiency in Attenuating Alternating Magnetic Fields
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Standards Content (Sample)

NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Contact ASTM International (www.astm.org) for the latest information
Designation: A698/A698M − 07
StandardTest Method for
Magnetic Shield Efficiency in Attenuating Alternating
1
Magnetic Fields
This standard is issued under the fixed designationA698/A698M; the number immediately following the designation indicates the year
of original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval.
A superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope 3.2 Definitions of Terms Specific to This Standard:
3.2.1 attenuation ratio—the ratio of the measured voltage in
1.1 This test method covers the means for determining the
thepickupcoilbeforeandaftertheinsertionoftheshieldunder
performance quality of a magnetic shield when placed in a
test, E /E .
1 2
magnetic field of alternating polarity.
3.3 Abbreviations:
1.2 This test method provides a means of evaluating and
3.3.1 A—ac ammeter (usually root mean square (rms) but
grading magnetic shielding materials to determine their suit-
may be peak reading type).
ability for use in the production of magnetic shields.
3.3.2 E —voltage in the pickup coil, after establishing the
1
1.3 This test method shall be used in conjunction with and
field of test but before insertion of the shield into the test
shall conform to the requirements of Practice A34/A34M.
position.
1.4 The values stated in either SI units or inch-pound units
3.3.3 E —highest voltage observed in the pickup coil, at the
2
are to be regarded separately as standard. The values stated in
field of test, while rotating the test shield in the test position.
each system may not be exact equivalents; therefore, each
3.3.4 H —magnetic field strength, Oe [A/m].
p
system shall be used independently of the other. Combining
values from the two systems may result in non-conformance 3.3.5 I —ac magnetizing current, peak amperes.
p
with the standard.
3.3.6 I—ac magnetizing current, rms amperes.
1.5 This standard does not purport to address all of the
3.3.7 l —length of demagnetizing air coil, cm [m].
c
safety concerns, if any, associated with its use. It is the
3.3.8 N—number of turns per coil section (one half of total
responsibility of the user of this standard to establish appro-
Helmholtz coil turns).
priate safety and health practices and determine the applica-
3.3.9 N —number of turns in demagnetizing coil.
bility of regulatory limitations prior to use. 1
3.3.10 R—mean radius of Helmholtz coil, cm [m].
2. Referenced Documents
3.3.11 V—electronic voltmeter (average volts 3π/2 =2).
2
2.1 ASTM Standards:
A34/A34M Practice for Sampling and Procurement Testing
4. Summary of Test Method
of Magnetic Materials
4.1 Frequency—Tests under this test method are normally
A340 Terminology of Symbols and Definitions Relating to
conducted at a test frequency of 60 Hz.
Magnetic Testing
NOTE 1—Other test frequencies are used by mutual agreement. In
3. Terminology
general, as test frequencies are increased, it will be necessary to make
corresponding changes in pickup or test coils and in the size of the power
3.1 The following symbols and abbreviated definitions ap-
supply.
plyonlytothistestmethod(theofficialsymbolsanddefinitions
4.2 Magnetic Field Strength—Tests may be conducted at
are listed in Terminology A340):
any desired magnetic field strength. The standard test level for
ac magnetic fields is 0.5 or 2.0 peak Oe [40 or 160 peak A/m]
1
This test method is under the jurisdiction of ASTM Committee A06 on
and in the presence of the earth’s magnetic field (see 9.2).
MagneticPropertiesandisthedirectresponsibilityofSubcommitteeA06.01onTest
Methods.
4.3 Instrumentation—The instruments described are for use
Current edition approved May 1, 2007. Published June 2007. Originally
at 60 Hz. At higher frequencies, electronic voltmeters and
approved in 1974. Last previous edition approved in 2002 as A698/A698M–02.
DOI: 10.1520/A0698_A0698M-07.
preamplifiers should also be satisfactory. It may be necessary
2
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
to change the rms ammeter and power supplies for use at
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
higher test frequencies. It may also be desirable to reduce the
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. number of area turns in the pickup coil at these frequencies.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
1

---------------------- Page: 1 ----------------------
A698/A698M − 07
4.4 Field Attenuation—The usable range of attenuation
ratios is determined by the strength of the starting field and the
sensitivity of the available instrumentation. Measurements
shall not be made when signal voltages cannot be clearly
distinguish
...

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5.1 This test method provides an easy, accurate, and reproducible method for determination of shielding factors (attenuation ratios) in simple alternating magnetic fields.  
5.2 Since the sensing or pickup coil is of finite size, the measured shielding factor tends to be the average value for the space enclosed by the coil. Due care is required when interpreting results when the coil is located near an opening in the shield.  
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5.1 These test methods are useful in research and quality control for evaluating insulating materials and systems since they provide for the measurement of charge transfer and energy loss due to partial discharges(4) (5) (6).  
5.2 Pulse measurements of partial discharges indicate the magnitude of individual discharges. However, if there are numerous discharges per cycle it is occasionally important to know their charge sum, since this sum is related to the total volume of internal gas spaces that are discharging, if it is assumed that the gas cavities are simple capacitances in series with the capacitances of the solid dielectrics (7) (8).  
5.3 Internal (cavity-type) discharges are mainly of the pulse (spark-type) with rapid rise times or the pseudoglow-type with long rise times, depending upon the discharge governing parameters existing within the cavity. If the rise times of the pseudoglow discharges are too long , they will evade detection by pulse detectors as covered in Test Method D1868. However, both the pseudoglow discharges irrespective of the length of their rise time as well as pulseless glow are readily measured either by Method A or B of Test Methods D3382.  
5.4 Pseudoglow discharges have been observed to occur in air, particularly when a partially conducting surface is involved. It is possible that such partially conducting surfaces will develop with polymers that are exposed to partial discharges for sufficiently long periods to accumulate acidic degradation products. Also in some applications, like turbogenerators, where a low molecular weight gas such as hydrogen is used as a coolant, it is possible that pseudoglow discharges will develop.
SCOPE
1.1 These test methods cover two bridge techniques for measuring the energy and integrated charge of pulse and pseudoglow partial discharges:  
1.2 Test Method A makes use of capacitance and loss characteristics such as measured by the transformer ratio-arm bridge or the high-voltage Schering bridge (Test Methods D150). Test Method A has been found useful to obtain the integrated charge transfer and energy loss due to partial discharges in a dielectric from the measured increase in capacitance and tan δ with voltage. (See also IEEE 286 and IEEE 1434)  
1.3 Test Method B makes use of a somewhat different bridge circuit, identified as a charge-voltage-trace (parallelogram) technique, which indicates directly on an oscilloscope the integrated charge transfer and the magnitude of the energy loss due to partial discharges.  
1.4 Both test methods are intended to supplement the measurement and detection of pulse-type partial discharges as covered by Test Method D1868, by measuring the sum of both pulse and pseudoglow discharges per cycle in terms of their charge and energy.  
1.5 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use. Specific precaution statements are given in Section 7.  
1.6 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.

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ASTM
ASTM D5388-21(Test Method)
Standard Test Method for Indirect Measurements of Discharge by Step-Backwater Method

SIGNIFICANCE AND USE
5.1 This test method is particularly useful for determining the discharge when it cannot be measured directly (such as during high flow conditions) by some type of current meter to obtain velocities and with sounding weights to determine the cross section (refer to Test Method D3858). This test method requires only one high-water elevation, unlike the slope-area test method that requires numerous high-water marks to define the fall in the reach. It can be used to determine a stage-discharge relation without data from several high-water events.  
5.1.1 The user is encouraged to verify the theoretical stage-discharge relation with direct current-meter measurements when possible.  
5.1.2 To develop a rating curve, plot stage versus discharge for several discharges and their computed stages on a rating curve together with direct current-meter measurements.
SCOPE
1.1 This test method covers the computation of discharge of water in open channels or streams using representative cross-sectional characteristics, the water-surface elevation of the upstream-most cross section, and coefficients of channel roughness as input to gradually-varied flow computations.2  
1.2 This test method produces an indirect measurement of the discharge for one flow event, usually a specific flood. The computed discharge may be used to define a point on the stage-discharge relation.  
1.3 The values stated in inch-pound units are to be regarded as standard. The values given in parentheses are mathematical conversions to SI units that are provided for information 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 responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.  
1.5 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.

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