ASTM E1458-12(2022)
(Test Method)Standard Test Method for Calibration Verification of Laser Diffraction Particle Sizing Instruments Using Photomask Reticles
Standard Test Method for Calibration Verification of Laser Diffraction Particle Sizing Instruments Using Photomask Reticles
SIGNIFICANCE AND USE
4.1 This test method permits a user to compare the performance of an instrument to the tolerance limit specifications stated by a manufacturer and to verify that an instrument is suitable for continued routine use. It also provides for generation of calibration data on a periodic basis, forming a database from which any changes in the performance of the instrument will be evident.
4.2 This test method for the calibration verification of laser diffraction particle sizing instruments is suitable for acceptance testing of laser diffraction instruments so long as current estimates of the bias (see Section 11) and the between-laboratory precision of the test method (see Section 10) are acceptably small relative to typical laser diffraction instrument accuracy specifications; see Practice D3244.
SCOPE
1.1 This test method describes a procedure necessary to permit a user to easily verify that a laser diffraction particle sizing instrument is operating within tolerance limit specifications, for example, such that the instrument accuracy is as stated by the manufacturer. The recommended calibration verification method provides a decisive indication of the overall performance of the instrument at the calibration point or points, but it is specifically not to be inferred that all factors in instrument performance are verified. In effect, use of this test method will verify the instrument performance for applications involving spherical particles of known refractive index where the near-forward light scattering properties are accurately modeled by the instrument data processing and data reduction software. The precision and bias limits presented herein are, therefore, estimates of the instrument performance under ideal conditions. Nonideal factors that could be present in actual applications and that could significantly increase the bias errors of laser diffraction instruments include vignetting4 (that is, where light scattered at large angles by particles far away from the receiving lens does not pass through the receiving lens and therefore does not reach the detector plane), the presence of nonspherical particles, the presence of particles of unknown refractive index, and multiple scattering.
1.2 This test method shall be used as a significant test of the instrument performance. While the procedure is not designed for extensive calibration adjustment of an instrument, it shall be used to verify quantitative performance on an ongoing basis, to compare one instrument performance with that of another, and to provide error limits for instruments tested.
1.3 This test method provides an indirect measurement of some of the important parameters controlling the results in particle sizing by laser diffraction. A determination of all parameters affecting instrument performance would come under a calibration adjustment procedure.
1.4 This test method shall be performed on a periodic and regular basis, the frequency of which depends on the physical environment in which the instrumentation is used. Thus, units handled roughly or used under adverse conditions (for example, exposed to dust, chemical vapors, vibration, or combinations thereof) shall undergo a calibration verification more frequently than those not exposed to such conditions. This procedure shall be performed after any significant repairs are made on an instrument, such as those involving the optics, detector, or electronics.
1.5 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
1.6 This standard does not purport to address all of the safety problems, 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.
1.7 This international standard was developed in accordance with internationally rec...
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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.
Designation:E1458 −12 (Reapproved 2022)
Standard Test Method for
Calibration Verification of Laser Diffraction Particle Sizing
Instruments Using Photomask Reticles
This standard is issued under the fixed designation E1458; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
INTRODUCTION
There exists a large variety of techniques and instruments for the sizing of particles and droplets in
fluid suspension. These instruments are based on a number of different physical phenomena and
interlaboratory comparisons of data on, for example, reference liquid sprays have shown significant
variability. This test method evolved in conjunction with efforts to explain the observed variability.
Theeffectivenessofthistestmethodcanbetracedtothefactitcircumventsdifficultiesassociatedwith
producing, replicating, and maintaining a standard sample of liquid particles in a spray. This test
method uses a photomask reticle to provide a simulation of some of the optical properties of a
referencepopulationofsphericalparticles.Thistestmethodisonlyapplicabletoopticalparticlesizing
instruments that are based on measurement and analysis of light scattered in the forward direction by
particles illuminated by a light beam. Since modern optical instruments generally use a laser to
produce a light beam, and since the light scattered in the forward direction by particles can often be
accurately described using diffraction theory approximations, the class of instruments for which this
test method applies have become generally known as laser diffraction particle sizing instruments.
2,3
Because it is specifically Fraunhofer diffraction theory that is used in the approximation, these
instruments are also known as Fraunhofer diffraction particle sizing instruments.
The diffraction approximation to the general problem of electromagnetic wave scattering by
particles is strictly valid only if three conditions are satisfied. The conditions are: particle sizes must
be significantly larger than the optical wavelength, particle refractive indices must be significantly
different than the surrounding medium, and only very small (near-forward) scattering angles are
considered. For the case of spherical particles with sizes on the order of the wavelength or for large
2,3
scattering angles, the complete Lorenz-Mie scattering theory rather than the Fraunhofer diffraction
approximation must be used. If the size and angle constraints are satisfied but the particle refractive
index is very close to that of the medium, the anomalous diffraction approximation may be used.
A complication is introduced by the fact that the optical systems of most laser diffraction particle
sizing instruments can be used, with only minor modifications such as changing a lens or translating
the sample, for measurement configurations outside the particle size or scattering angle range for
which the diffraction approximation is valid. In this situation the scattering inversion software in the
instrumentwouldgenerallyincorporateascatteringmodelotherthanFraunhoferdiffractiontheory,in
whichcasetheterm“laserdiffractioninstrument”mightbeconsideredamisnomer.However,suchan
instrumentisstillinessencealaserdiffractioninstrument,modifiedtodecreasethelowerparticlesize
limit.Acalibration verification procedure as described by this test method would be applicable to all
instrumentconfigurations(oroperationalmodes)wherethephotomaskreticleaccuratelysimulatesthe
relevant optical properties of the particles.
The ideal calibration test samples for laser diffraction particle sizing instruments would be
comprised of the actual particle or droplet material of interest in the actual environment of interest
with size distributions closely approximating those encountered in practice. However, the use of such
calibration test samples is not currently feasible because multi-phase mixtures may undergo changes
during a test and because actual samples (for example, a spray) are not easily collected and stabilized
for long periods of time. The subject of this test method is an alternative calibration test sample
comprised of a two-dimensional array of thin, opaque circular discs (particle artifacts) deposited on
a transparent substrate (the photographic negative, that is, clear apertures in an opaque substrate, may
beusedaswell).Eachdiscorparticleartifactrepresentstheorthogonalprojectionofthecross-section
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
E1458−12 (2022)
of one member of a population of spherical particles comprising the reference population. The
collectionofparticleartifactsonareticlerepresentsanorthogonalprojectionofalltheparticlesinthe
reference population for one particular three-dimensional arrangement of the population where the
member particles are positioned within a finite reference volume. The reference volume is generally
defined such that the area covered by particle artifacts on the reticle is roughly equivalent to the
cross-section of the instrument light beam. The reference population would generally contain a large
number of particles, with a size distribution that approximates distributions of practical interest,
randomly distributed over the reference volume. Large numbers and random positions minimize
complications that can arise from optical coherence effects (interference).
Of importance here is the fact that the near-forward scattering characteristics of the orthogonal
projections of the particle cross-sections onto the reticle plane accurately simulate, in regimes where
the diffraction approximation is valid, the near-forward scattering characteristics of the reference
population (independent of the chemical composition of the particles in the reference population). In
otherwordsthephotomaskreticle,whenilluminatedwithalaserbeamofknownproperties,generates
a reference scattered light signature which can be predicted analytically from a knowledge of the size
distribution of the reference population. The properties of the reference population can be inferred
from a characterization (using optical microscopy) of the sizes of the particle artifacts on the reticle.
As the instrument is operated away from the diffraction regime, the scattering properties of the
photomask reticle diverge from that which would be produced by the reference population and
interpretation of the measurements becomes more problematic.
The most complete test result for this test method would be a discrete size distribution reported for
averylargenumberofsizeclassintervals,butintercomparisonsofsuchdistributionsaredifficult.For
that reason statistical parameters (for example, representative diameters and measures of the
dispersion) of the particle size distribution are used. Two examples of statistical parameters are the
volumemediandiameter D andtherelativespan(D − D )/D asdefinedinPracticeE799
V0.5 V0.9 V0.1 V0.5
(recall that volume parameters such as D for a photomask reticle are defined in the sense that
Vf
two-dimensionalparticleartifactsscatterlightlikesphericalparticlesofthesamediameter).Estimates
of the true values of these statistical parameters for a photomask reticle (or more precisely the true
values for the reference population simulated by the reticle) can be established using optical or
electron microscope measurements of the diameters of the particle artifacts on the reticle. The values
so established are termed image-analysis reference values and will be used herein as the accepted
reference values. It is the stability of D , the relative span, and all other statistical parameters
V0.5
representative of the particle artifact size distribution for a reticle and the ability to produce nearly
identical replicate copies of the reticles that make this test method useful. A comparison of the
accepted reference value of D , the relative span, or any other parameter of a reticle with a
V0.5
corresponding test result from the instrument under evaluation can be used to assess the acceptability
of the instrument and of the data routinely obtained with the instrument.
This test method is under the jurisdiction ofASTM Committee E29 on Particle and Spray Characterization and is the direct responsibility of Subcommittee E29.02 on
Non-Sieving Methods.
Current edition approved Feb. 1, 2022. Published April 2022. Originally approved in 1992. Last previous edition approved in 2016 as E1458 – 12 (2016). DOI:
10.1520/E1458-12R22.
Bohren, C.F., and Huffman, D.R., Absorption and Scattering of Light by Small Particles, John Wiley and Sons, New York, 1983.
van de Hulst, H.C., Light Scattering by Small Particles, Dover Publications Inc., New York, 1981.
1. Scope modeled by the instrument data processing and data reduction
software. The precision and bias limits presented herein are,
1.1 This test method describes a procedure necessary to
therefore, estimates of the instrument performance under ideal
permit a user to easily verify that a laser diffraction particle
conditions. Nonideal factors that could be present in actual
sizing instrument is operating within tolerance limit
applicationsandthatcouldsignificantlyincreasethebiaserrors
specifications, for example, such that the instrument accuracy 4
of laser diffraction instruments include vignetting (that is,
is as stated by the manufacturer.The recommended calibration
wherelightscatteredatlargeanglesbyparticlesfarawayfrom
verification method provides a decisive indication of the
the receiving lens does not pass through the receiving lens and
overall performance of the instrument at the calibration point
therefore does not reach the detector plane), the presence of
or points, but it is specifically not to be inferred that all factors
ininstrumentperformanceareverified.Ineffect,useofthistest
methodwillverifytheinstrumentperformanceforapplications
Hirleman, E.D., Oechsle, V., and Chigier, N.A., “Response Characteristics of
involving spherical particles of known refractive index where
Laser Diffraction Particle Sizing Systems: Optical Sample Volume and Lens
the near-forward light scattering properties are accurately Effects,” Optical Engineering, Vol 23, 1984, pp. 610–619.
E1458−12 (2022)
nonspherical particles, the presence of particles of unknown E799Practice for Determining Data Criteria and Processing
refractive index, and multiple scattering. for Liquid Drop Size Analysis
E1187Terminology Relating to Conformity Assessment
1.2 Thistestmethodshallbeusedasasignificanttestofthe
(Withdrawn 2006)
instrument performance. While the procedure is not designed
2.2 Military Standard:
for extensive calibration adjustment of an instrument, it shall
MIL-STD-45662Calibration Systems Requirements
beusedtoverifyquantitativeperformanceonanongoingbasis,
2.3 NIST Standard:
to compare one instrument performance with that of another,
NIST SP 676-1Measurement Assurance Programs
and to provide error limits for instruments tested.
2.4 ANSI Standard:
1.3 This test method provides an indirect measurement of
ANSI-ASQC Z-1Standard for Calibration Systems
some of the important parameters controlling the results in
2.5 ISO Standard:
particle sizing by laser diffraction. A determination of all
ISO Guide 2AGeneral Terms and Their Definitions Con-
parameters affecting instrument performance would come
cerning Standardization Certification, and Testing Lab.
under a calibration adjustment procedure.
Accreditation
1.4 This test method shall be performed on a periodic and
3. Terminology
regular basis, the frequency of which depends on the physical
environment in which the instrumentation is used. Thus, units 3.1 Current ASTM Standard Definitions—Definitions of the
terms listed below, as used in this test method are from the
handled roughly or used under adverse conditions (for
Compilation of ASTM Standard Definitions:
example, exposed to dust, chemical vapors, vibration, or
3.1.1 accuracy—see Terminology D123, (Committee D13).
combinations thereof) shall undergo a calibration verification
more frequently than those not exposed to such conditions.
3.1.2 assignable cause—see Terminology E456, (Commit-
This procedure shall be performed after any significant repairs
tee E11).
are made on an instrument, such as those involving the optics,
3.1.3 bias—see Terminology D123, (Committee D13).
detector, or electronics.
3.1.4 calibration—see Terminology E1187, (Committee
1.5 The values stated in SI units are to be regarded as
E36).
standard. No other units of measurement are included in this
3.1.5 Discussion—This and many other commonly used
standard.
definitions for calibration are very broad in the sense that they
1.6 This standard does not purport to address all of the
could encompass a wide range of tasks. (See for example
safety problems, if any, associated with its use. It is the
MIL-STD-45662, NISTSP676-1, andANSI-ASQC Z-1 Draft
responsibility of the user of this standard to establish appro-
StandardforCalibrationSystems).Forexample,insomecases
priate safety, health, and environmental practices and deter-
calibration is only the determination of whether or not an
mine the applicability of regulatory limitations prior to use.
instrument is operating within accuracy specifications (toler-
1.7 This international standard was developed in accor-
ance testing in NIST SP 676-1). In other cases calibration
dance with internationally recognized principles on standard-
includes reporting of differences between the instrument re-
ization established in the Decision on Principles for the
sponse and the accepted value of the standard, for example, to
Development of International Standards, Guides and Recom-
produce a “Table of Corrections” to be used with the instru-
mendations issued by the World Trade Organization Technical
ment. Finally, calibration can also include any repairs or
Barriers to Trade (TBT) Committee.
adjustments required to make the instrument response consis-
tentwiththestandardwithinthestatedaccuracyspecifications.
2. Referenced Documents
To clarify the situation it is proposed that the more specific
2.1 ASTM Standards:
terms calibration verification and calibration adjustment (see
A340Terminology of Symbols and Definitions Relating to
3.4) both of which would fall under these broad definitions of
Magnetic Testing
calibration.
D123Terminology Relating to Textiles
3.1.6 coeffıcient
...
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