ISO 13323-1:2000

Determination of particle size distribution - Single-particle light interaction methods - Part 1: Light interaction considerations

Détermination de la distribution granulométrique — Méthodes d'interaction lumineuse de particules uniques — Partie 1: Considérations relatives à l'interaction lumineuse

Določevanje granulacije - Metode z interakcijo svetlobe in posameznih delcev - 1. del: Ocenitve na osnovi interakcije svetlobe

General Information

• Status: Withdrawn
• Publication Date: 01-Nov-2000
• Withdrawal Date: 01-Nov-2000
• ICS: 19.120 - Particle size analysis. Sieving
• Technical Committee: ISO/TC 24/SC 4 - Particle characterization
• Drafting Committee: ISO/TC 24/SC 4/WG 9 - Single particle light interaction methods
• Current Stage: 9599 - Withdrawal of International Standard
• Start Date: 07-May-2007
• Completion Date: 13-Dec-2025
• Ref Project: SIST ISO 13323-1:2002 - Determination of particle size distribution -- Single-particle light interaction methods -- Part 1: Light interaction considerations

Relations

• Revised: ISO 21501-2:2007 - Determination of particle size distribution - Single particle light interaction methods - Part 2: Light scattering liquid-borne particle counter
• Effective Date: 15-Apr-2008
• Revised: ISO 21501-4:2007 - Determination of particle size distribution - Single particle light interaction methods - Part 4: Light scattering airborne particle counter for clean spaces
• Effective Date: 15-Apr-2008
• Revised: ISO 21501-3:2007 - Determination of particle size distribution - Single particle light interaction methods - Part 3: Light extinction liquid-borne particle counter
• Effective Date: 15-Apr-2008

Standards Content (Sample)

SLOVENSKI STANDARD
01-junij-2002
'RORþHYDQMHJUDQXODFLMH0HWRGH]LQWHUDNFLMRVYHWOREHLQSRVDPH]QLKGHOFHY
GHO2FHQLWYHQDRVQRYLLQWHUDNFLMHVYHWOREH
Determination of particle size distribution -- Single-particle light interaction methods --
Part 1: Light interaction considerations
Détermination de la distribution granulométrique -- Méthodes d'interaction lumineuse de
particules uniques -- Partie 1: Considérations relatives à l'interaction lumineuse
Ta slovenski standard je istoveten z: ISO 13323-1:2000
ICS:
19.120 Analiza velikosti delcev. Particle size analysis. Sieving
Sejanje
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

INTERNATIONAL ISO
STANDARD 13323-1
First edition
2000-11-01
Determination of particle size
distribution — Single-particle light
interaction methods —
Part 1:
Light interaction considerations
Détermination de la distribution granulométrique — Méthodes d'interaction
lumineuse de particules uniques —
Partie 1: Considérations relatives à l'interaction lumineuse
Reference number
©
ISO 2000
PDF disclaimer
This PDF file may contain embedded typefaces. In accordance with Adobe's licensing policy, this file may be printed or viewed but shall not
be edited unless the typefaces which are embedded are licensed to and installed on the computer performing the editing. In downloading this
file, parties accept therein the responsibility of not infringing Adobe's licensing policy. The ISO Central Secretariat accepts no liability in this
area.
Adobe is a trademark of Adobe Systems Incorporated.
Details of the software products used to create this PDF file can be found in the General Info relative to the file; the PDF-creation parameters
were optimized for printing. Every care has been taken to ensure that the file is suitable for use by ISO member bodies. In the unlikely event
that a problem relating to it is found, please inform the Central Secretariat at the address given below.
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form or by any means, electronic
or mechanical, including photocopying and microfilm, without permission in writing from either ISO at the address below or ISO's member body
in the country of the requester.
ISO copyright office
Case postale 56 � CH-1211 Geneva 20
Tel. + 41 22 749 01 11
Fax + 41 22 749 09 47
E-mail [e-mail]
Web www.iso.ch
Printed in Switzerland
ii © ISO 2000 – All rights reserved

Contents Page
Foreword.iv
Introduction.v
1 Scope .1
2 Normative references .1
3 Terms and definitions .2
3.1 Definitions .2
3.2 Symbols .3
4 Light interaction principles.4
4.1 Introduction.4
4.2 Light scattering.4
4.3 Light extinction .6
5 Performance of particle measurement device.7
5.1 Particle-sizing accuracy.7
5.2 Particle-sizing resolution .7
5.3 Particle-counting accuracy and concentration limits.8
6 Particle-counter operation.8
6.1 Environmental constraints .8
6.2 Sample-acquisition requirements.9
Annex A (normative) Theoretical background of light scattering.10
Annex B (informative) Theoretical background of light extinction .12
Annex C (informative) Applications for single-particle light interaction devices.14
Bibliography.15
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies (ISO
member bodies). The work of preparing International Standards is normally carried out through ISO technical
committees. Each member body interested in a subject for which a technical committee has been established has
the right to be represented on that committee. International organizations, governmental and non-governmental, in
liaison with ISO, also take part in the work. ISO collaborates closely with the International Electrotechnical
Commission (IEC) on all matters of electrotechnical standardization.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 3.
Draft International Standards adopted by the technical committees are circulated to the member bodies for voting.
Publication as an International Standard requires approval by at least 75 % of the member bodies casting a vote.
Attention is drawn to the possibility that some of the elements of this part of ISO 13323 may be the subject of
patent rights. ISO shall not be held responsible for identifying any or all such patent rights.
International Standard ISO 13323-1 was prepared by Technical Committee ISO/TC 24, Sieves, sieving and other
sizing methods, Subcommittee SC 4, Sizing by methods other than sieving.
ISO 13323 consists of the following parts, under the general title Determinatrion of particle size distribution —
Single-particle light interaction methods:
� Part 1: Light interaction considerations
� Part 2: Light-scattering single-particle light interaction device design, performance specifications and operation
requirements
� Part 3: Single-particle light-extinction device design, performance specifications and operation requirements
Annexes A, B and C of this part of ISO 13323-1 are for information only.
iv © ISO 2000 – All rights reserved

Introduction
Measurement of individual particles by interaction with light has been carried out for many years using a variety of
instruments. These instruments vary in optical design, light-source types, and means of particle presentation to the
light. For these reasons, data from nearly identical particle sources frequently differ when different instruments are
used for measurement. In addition, the extent of light interaction produced by a particle is affected by several
physical parameters in addition to the particle size. The purpose of this part of ISO 13323 is to define the basis for,
and to reduce the variability of, data produced by light interaction methods of particle size measurement.
Particle size measurement by single-particle light interaction devices normally involves either determination of the
light scattered as a result of the light interaction with a single-particle or the amount of light extinction caused by the
presence of the particle in the light beam. This part of ISO 13323 will discuss the principle of the light interaction
phenomena that are measured. The general performance and operational parameters that are pertinent to the
instruments and to the particle/fluid environment in which the instruments operate will be summarized. Specific
instrument types, operation, and performance are not discussed in this part of ISO 13323.
INTERNATIONAL STANDARD ISO 13323-1:2000(E)
Determination of particle size distribution — Single-particle light
interaction methods —
Part 1:
Light interaction considerations
1 Scope
This part of ISO 13323 provides guidance on the selection and operation of devices that determine the size and
number of particles by measuring the phenomena resulting from light interaction with individual particles present in
a gas or liquid. The reported particle size is defined as an equivalent optical size based upon the response of the
measurement system to calibration particles. This definition requires that the instrument be calibrated with well-
defined materials.
This part of ISO 13323 applies to particles ranging in size from approximately 0,05µm in diameter to the millimetre
size range. Gas-borne particles in sizes from approximately 0,05µm to 20µm or so are measured primarily by
light-scattering. Larger particles can be measured using light extinction sensors. Liquid-borne particles in the size
range from approximately 0,05µm to a few micrometres are measured by light-scattering. Light extinction is used
to measure liquid-borne particles in sizes from approximately 1µm to the millimetre size range. The size range
capability of any single instrument is usually approximately 100:1. Particles larger than approximately 100 times the
size of the smallest particle that can be measured with good sizing resolution are reported as “greater than or equal
to the threshold size” of the largest size channel of the instrument.
The response that is considered in this part of ISO 13323 is the change in collected light flux resulting from the
presence of a single-particle within the optical sensing zone of the measuring instrument. For this reason,
instruments, which rely upon optical interaction to produce data only indicating the extent of particle motion, are not
discussed here.
NOTE Instruments not discussed here include devices such as aerodynamic particle sizers or phase Doppler particle
analysers, which produce data primarily dependent upon the aerodynamic size of the particles. Those instrument types do not
use the extent of light interaction to measure the particle size. The particle size is defined by residence time during motion
through a defined distance or by particle velocity. These instruments report a particle size that is related to fluid-dynamic
measurements.
2 Normative references
The following normative documents contain provisions which, through reference in this text, constitute provisions of
this part of ISO 13323. For dated references, subsequent amendments to, or revisions of, any of these publications
do not apply. However, parties to agreements based on this part of ISO 13323 are encouraged to investigate the
possibility of applying the most recent editions of the normative documents indicated below. For undated
references, the latest edition of the normative document referred to applies. Members of ISO and IEC maintain
registers of currently valid International Standards.
ISO 3165, Sampling of chemical products for industrial use — Safety in sampling.
ISO 6206, Chemical products for industrial use — Sampling — Vocabulary.
1)
ISO 14887 , Sample preparation — Dispersing procedures for powders in liquid.
3 Terms and definitions
For the purposes of this part of ISO 13323, the following terms, definitions and symbols apply.
3.1 Definitions
3.1.1
absorption
reduction of intensity of a light beam traversing a medium (fluid or particle) by energy conversion in the medium
3.1.2
coincidence
presence of more than one particle within the sensing zone of an instrument at any time
NOTE The effects include decreased indication of particle population and increased indication of particle size, since
several particles can be reported as a single larger one.
3.1.3
relative complex refractive index
refractive index of a particle relative to that of the fluid medium (n ) in which it is suspended, consisting of a real
m
part (n ) and an imaginary (absorption) part (ik )
p p
ni�k
p p
m � (1)
n
m
3.1.4
counting accuracy
ratio of the reported population to the true population in the measured sample
NOTE The counting accuracy may be expressed as counting efficiency by multiplying the ratio by 100.
3.1.5
equivalent optical diameter
diameter reported by a single-particle light interaction device, based upon the light interaction signal from that
single-particle being equivalent to that from a calibration particle of known dimensions and optical properties
NOTE This diameter will vary with the optical system of the device and particle/fluid optical properties and some physical
properties.
3.1.6
extinction
attenuation of light through absorption and scattering when passing through or otherwise interacting with a medium
3.1.7
multiple scattering
three-dimensional spatial pattern of light intensity emitted from a particle from scattering of light from the primary
light source and light scattered from other particles in the sensing volume which is directed to the particle of
concern in the sensing zone
3.1.8
reflection
return of radiation by a surface without change in wavelength
1) To be published.
2 © ISO 2000 – All rights reserved

3.1.9
refractive index
ratio of the velocity of light in a medium to the velocity in a vacuum which is expressed as the combination of a real
and an imaginary term
NOTE The real term expresses the light velocity ratio and the imaginary term expresses the fraction of incident light
absorbed by the medium through which the light passes.
3.1.10
refraction
change in the direction of light propagation as a result of change in the velocity of propagation in passing from one
medium to another
3.1.11
reported size range
size channel
size range defined by a particle sizing instrument
NOTE When several size ranges are reported, the lower and upper range limits are shown. The upper limit of all but the
largest size range is equal to the lower limit of the next larger range. The size limits of the largest range is typically defined as
“equal to or greater than x”, where x is the lowest size limit of that range.
3.1.12
scattering
general term describing the change in light propagation at the interface of two media
3.1.13
scattering pattern
three-dimensional spatial pattern of light intensity emitted from a particle as a result of scattering of light transmitted
from the primary light source to the particle being measured in the optical sensing zone
3.1.14
sensing zone
sensing volume
volume within the instrument that is optically and physically defined where particle interaction with light is observed
and used to develop data on particle size and quantity
3.1.5
Stoke's number
St
product of particle relaxation time (t), time for a particle to accommodate to a fluid velocity change and actual
particle velocity (v), divided by the sample probe inlet size (d )
i
tv
St � (2)
d
i
3.1.6
extinction coefficient
E
ratio of total light flux scattered and/or absorbed by a particle to the light flux incident upon the particle
3.2 Symbols
a Particle radius
A Projected area of particle(s) illuminated by incident light
c Numerical particle concentration
n
E Extinction coefficient
I(�) Angular intensity distribution of light scattered by a particle
I(r) Light flux scattered by a particle at a specific solid angle
I Scattered light polarized in a direction perpendicular to the incident light beam
I Scattered ight polarized in a direction parallel to the incident light beam
k Imaginary (absorption) part of a particle refractive index
p
l Beam path through a sensing zone
n Refractive index of a particle, relative to that of the suspension medium
n Real part of the refractive index of the suspension medium
m
n Real part of the refractive index of the particle
p
x Particle diameter, in micrometres. Unless otherwise specified, the equivalent optical diameter is reported
y Ratio of scattered or transmitted light flux to incident light flux
� The term of particle projected area divided by the illumination wavelength, 2�A/�
� Scattering angle with respect to forward direction in degrees. The scattering angle may consist of a
significantly large solid angle, but is typically defined as the centre angle of the light collection system with
respect to the centre line of the illumination source
� Wavelength of the illumination source, in nanometres. The illumination source may emit light at a single
wavelength or over a broad range of wavelengths
4 Light interaction principles
4.1 Introduction
A brief summary of the parameters affecting light interaction with single-particles is presented in this clause. Further
details are provided in annex A. In single-particle light interaction devices, the output data are affected by
illumination wavelength and intensity, illumination source and collection optics configurations, as well as light
collection and capabilities of the data handling system. Particle and suspension fluid physical properties affect
response, as well. The particle size, shape, and orientation within the sensing zone may also affect the response.
The relative refractive index of the particle in the suspension fluid also affects the response.
4.2 Light scattering
Most particles measured by light-scattering will be in the size range from approximately 50 nm to 100µm. When
light interacts with the particle, the scattered light flux varies roughly with the projected area of the particle for
particles with radius significantly larger than the light wavelength. For smaller particles, the variation of the
scattered light flux changes with particle radius, increasing to the sixth power as particle size decreases to
approximately 0,2µm. A light-scattering system used for submicrometer particles will normally be used to measure
particles over a size range up to 50:1. A system that is used to measure particles larger than approximately 1µm
can measure over a size range of approximately 100:1. The limitations are connected with the linearity of electronic
data processing systems over wide ranges (e.g. 5� 10 ) and the need to ensure that the smallest signal that is
processed is larger than the electronic and optical background noise level.
NOTE Further details on the operation of light-scattering instruments for counting and/or sizing particles can be obtained
[3]
from the reference in the bibliography.
4 © ISO 2000 – All rights reserved

4.2.1 Physical principles
Measurement of scattered light from fluidborne particles is carried out by observing the scattered light from the
particle at a specific solid angle that is defined by a particular instrument configuration. The particle(s) within the
sensing zone of the instrument may be present within a known volume of fluid moved through the instrument or
may be moving with “normal” fluid flow through a defined known sensing zone established within the instrument. In
the first case, the particle concentration per unit fluid volume is defined; in the second case, the particle flux per unit
area through which particles are moving is defined on a time basis. The instruments which report the particle
concentration are normally used to characterize particle size distribution and concentration in fluids which are
moving under specific conditions at pressures ranging from near ambient to approximately 500 kPa. Instruments
defining particle flux are often used when flow is random or at pressures from approximately 1 kPa to ambient.
4.2.2 Optical system designs
Typical optical system bases for single-particle light-scattering instruments are shown in Figure 1. The
configurations shown here describe essentially every optical design of the light-scattering instrument used for this
purpose. The original designs, laid out in 1965, used incandescent-filament illumination sources, lens and aperture
systems to define sensing zones. A summary of single-particle light-scattering instruments designed for aerosol
studies was shown recently. Current optical systems use either gas or diode-laser illumination that may not require
the same type of beam-shaping systems. Even so, the basic optical system designs for light collection are still
followed. The choice for selection is based upon the particle size range of concern, available components,
construction funds, and the environments in which particle measurements are to be made. Essentially, the same
optical design base can be used for measurements in gas or in liquid suspension. The major differences are in the
fluid control systems used for the two applications. The problems of defining the edges of the sensing zones are
greater when working with liquid systems. Larger particles are more frequently measured in liquid than in gas and a
small portion of a liquid-borne large particle may move through an optically defined sensing zone, scattering as
much light as a small particle entirely within the sensing zone. Procedures for minimizing this effect and other
problem areas will be discussed in ISO 13323-2 and ISO 13323-3.
[4]
NOTE Further information on the optical design of airborne-particle counting systems can be obtained from reference in
the bibliography.
In general, particle counters using monochromatic light sources and forward-scattering systems with a small solid
angle produce a multi-valued response of scattered light flux as a function of particle size. The response will
increase and decrease with particle size over some portions of the instrument dynamic range. Particle counters
with polychromatic light, and especially those with scattering systems with a large solid angle, produce the
desirable response where scattered light flux does not increase and decrease as the particle size increases, but the
instrument sensitivity for small particle measurement may be decreased unless illumination intensity is increased
and the design of the optical and electronic systems minimizes b
...

INTERNATIONAL ISO
STANDARD 13323-1
First edition
2000-11-01
Determination of particle size
distribution — Single-particle light
interaction methods —
Part 1:
Light interaction considerations
Détermination de la distribution granulométrique — Méthodes d'interaction
lumineuse de particules uniques —
Partie 1: Considérations relatives à l'interaction lumineuse
Reference number
©
ISO 2000
PDF disclaimer
This PDF file may contain embedded typefaces. In accordance with Adobe's licensing policy, this file may be printed or viewed but shall not
be edited unless the typefaces which are embedded are licensed to and installed on the computer performing the editing. In downloading this
file, parties accept therein the responsibility of not infringing Adobe's licensing policy. The ISO Central Secretariat accepts no liability in this
area.
Adobe is a trademark of Adobe Systems Incorporated.
Details of the software products used to create this PDF file can be found in the General Info relative to the file; the PDF-creation parameters
were optimized for printing. Every care has been taken to ensure that the file is suitable for use by ISO member bodies. In the unlikely event
that a problem relating to it is found, please inform the Central Secretariat at the address given below.
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form or by any means, electronic
or mechanical, including photocopying and microfilm, without permission in writing from either ISO at the address below or ISO's member body
in the country of the requester.
ISO copyright office
Case postale 56 � CH-1211 Geneva 20
Tel. + 41 22 749 01 11
Fax + 41 22 749 09 47
E-mail [e-mail]
Web www.iso.ch
Printed in Switzerland
ii © ISO 2000 – All rights reserved

Contents Page
Foreword.iv
Introduction.v
1 Scope .1
2 Normative references .1
3 Terms and definitions .2
3.1 Definitions .2
3.2 Symbols .3
4 Light interaction principles.4
4.1 Introduction.4
4.2 Light scattering.4
4.3 Light extinction .6
5 Performance of particle measurement device.7
5.1 Particle-sizing accuracy.7
5.2 Particle-sizing resolution .7
5.3 Particle-counting accuracy and concentration limits.8
6 Particle-counter operation.8
6.1 Environmental constraints .8
6.2 Sample-acquisition requirements.9
Annex A (normative) Theoretical background of light scattering.10
Annex B (informative) Theoretical background of light extinction .12
Annex C (informative) Applications for single-particle light interaction devices.14
Bibliography.15
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies (ISO
member bodies). The work of preparing International Standards is normally carried out through ISO technical
committees. Each member body interested in a subject for which a technical committee has been established has
the right to be represented on that committee. International organizations, governmental and non-governmental, in
liaison with ISO, also take part in the work. ISO collaborates closely with the International Electrotechnical
Commission (IEC) on all matters of electrotechnical standardization.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 3.
Draft International Standards adopted by the technical committees are circulated to the member bodies for voting.
Publication as an International Standard requires approval by at least 75 % of the member bodies casting a vote.
Attention is drawn to the possibility that some of the elements of this part of ISO 13323 may be the subject of
patent rights. ISO shall not be held responsible for identifying any or all such patent rights.
International Standard ISO 13323-1 was prepared by Technical Committee ISO/TC 24, Sieves, sieving and other
sizing methods, Subcommittee SC 4, Sizing by methods other than sieving.
ISO 13323 consists of the following parts, under the general title Determinatrion of particle size distribution —
Single-particle light interaction methods:
� Part 1: Light interaction considerations
� Part 2: Light-scattering single-particle light interaction device design, performance specifications and operation
requirements
� Part 3: Single-particle light-extinction device design, performance specifications and operation requirements
Annexes A, B and C of this part of ISO 13323-1 are for information only.
iv © ISO 2000 – All rights reserved

Introduction
Measurement of individual particles by interaction with light has been carried out for many years using a variety of
instruments. These instruments vary in optical design, light-source types, and means of particle presentation to the
light. For these reasons, data from nearly identical particle sources frequently differ when different instruments are
used for measurement. In addition, the extent of light interaction produced by a particle is affected by several
physical parameters in addition to the particle size. The purpose of this part of ISO 13323 is to define the basis for,
and to reduce the variability of, data produced by light interaction methods of particle size measurement.
Particle size measurement by single-particle light interaction devices normally involves either determination of the
light scattered as a result of the light interaction with a single-particle or the amount of light extinction caused by the
presence of the particle in the light beam. This part of ISO 13323 will discuss the principle of the light interaction
phenomena that are measured. The general performance and operational parameters that are pertinent to the
instruments and to the particle/fluid environment in which the instruments operate will be summarized. Specific
instrument types, operation, and performance are not discussed in this part of ISO 13323.
INTERNATIONAL STANDARD ISO 13323-1:2000(E)
Determination of particle size distribution — Single-particle light
interaction methods —
Part 1:
Light interaction considerations
1 Scope
This part of ISO 13323 provides guidance on the selection and operation of devices that determine the size and
number of particles by measuring the phenomena resulting from light interaction with individual particles present in
a gas or liquid. The reported particle size is defined as an equivalent optical size based upon the response of the
measurement system to calibration particles. This definition requires that the instrument be calibrated with well-
defined materials.
This part of ISO 13323 applies to particles ranging in size from approximately 0,05µm in diameter to the millimetre
size range. Gas-borne particles in sizes from approximately 0,05µm to 20µm or so are measured primarily by
light-scattering. Larger particles can be measured using light extinction sensors. Liquid-borne particles in the size
range from approximately 0,05µm to a few micrometres are measured by light-scattering. Light extinction is used
to measure liquid-borne particles in sizes from approximately 1µm to the millimetre size range. The size range
capability of any single instrument is usually approximately 100:1. Particles larger than approximately 100 times the
size of the smallest particle that can be measured with good sizing resolution are reported as “greater than or equal
to the threshold size” of the largest size channel of the instrument.
The response that is considered in this part of ISO 13323 is the change in collected light flux resulting from the
presence of a single-particle within the optical sensing zone of the measuring instrument. For this reason,
instruments, which rely upon optical interaction to produce data only indicating the extent of particle motion, are not
discussed here.
NOTE Instruments not discussed here include devices such as aerodynamic particle sizers or phase Doppler particle
analysers, which produce data primarily dependent upon the aerodynamic size of the particles. Those instrument types do not
use the extent of light interaction to measure the particle size. The particle size is defined by residence time during motion
through a defined distance or by particle velocity. These instruments report a particle size that is related to fluid-dynamic
measurements.
2 Normative references
The following normative documents contain provisions which, through reference in this text, constitute provisions of
this part of ISO 13323. For dated references, subsequent amendments to, or revisions of, any of these publications
do not apply. However, parties to agreements based on this part of ISO 13323 are encouraged to investigate the
possibility of applying the most recent editions of the normative documents indicated below. For undated
references, the latest edition of the normative document referred to applies. Members of ISO and IEC maintain
registers of currently valid International Standards.
ISO 3165, Sampling of chemical products for industrial use — Safety in sampling.
ISO 6206, Chemical products for industrial use — Sampling — Vocabulary.
1)
ISO 14887 , Sample preparation — Dispersing procedures for powders in liquid.
3 Terms and definitions
For the purposes of this part of ISO 13323, the following terms, definitions and symbols apply.
3.1 Definitions
3.1.1
absorption
reduction of intensity of a light beam traversing a medium (fluid or particle) by energy conversion in the medium
3.1.2
coincidence
presence of more than one particle within the sensing zone of an instrument at any time
NOTE The effects include decreased indication of particle population and increased indication of particle size, since
several particles can be reported as a single larger one.
3.1.3
relative complex refractive index
refractive index of a particle relative to that of the fluid medium (n ) in which it is suspended, consisting of a real
m
part (n ) and an imaginary (absorption) part (ik )
p p
ni�k
p p
m � (1)
n
m
3.1.4
counting accuracy
ratio of the reported population to the true population in the measured sample
NOTE The counting accuracy may be expressed as counting efficiency by multiplying the ratio by 100.
3.1.5
equivalent optical diameter
diameter reported by a single-particle light interaction device, based upon the light interaction signal from that
single-particle being equivalent to that from a calibration particle of known dimensions and optical properties
NOTE This diameter will vary with the optical system of the device and particle/fluid optical properties and some physical
properties.
3.1.6
extinction
attenuation of light through absorption and scattering when passing through or otherwise interacting with a medium
3.1.7
multiple scattering
three-dimensional spatial pattern of light intensity emitted from a particle from scattering of light from the primary
light source and light scattered from other particles in the sensing volume which is directed to the particle of
concern in the sensing zone
3.1.8
reflection
return of radiation by a surface without change in wavelength
1) To be published.
2 © ISO 2000 – All rights reserved

3.1.9
refractive index
ratio of the velocity of light in a medium to the velocity in a vacuum which is expressed as the combination of a real
and an imaginary term
NOTE The real term expresses the light velocity ratio and the imaginary term expresses the fraction of incident light
absorbed by the medium through which the light passes.
3.1.10
refraction
change in the direction of light propagation as a result of change in the velocity of propagation in passing from one
medium to another
3.1.11
reported size range
size channel
size range defined by a particle sizing instrument
NOTE When several size ranges are reported, the lower and upper range limits are shown. The upper limit of all but the
largest size range is equal to the lower limit of the next larger range. The size limits of the largest range is typically defined as
“equal to or greater than x”, where x is the lowest size limit of that range.
3.1.12
scattering
general term describing the change in light propagation at the interface of two media
3.1.13
scattering pattern
three-dimensional spatial pattern of light intensity emitted from a particle as a result of scattering of light transmitted
from the primary light source to the particle being measured in the optical sensing zone
3.1.14
sensing zone
sensing volume
volume within the instrument that is optically and physically defined where particle interaction with light is observed
and used to develop data on particle size and quantity
3.1.5
Stoke's number
St
product of particle relaxation time (t), time for a particle to accommodate to a fluid velocity change and actual
particle velocity (v), divided by the sample probe inlet size (d )
i
tv
St � (2)
d
i
3.1.6
extinction coefficient
E
ratio of total light flux scattered and/or absorbed by a particle to the light flux incident upon the particle
3.2 Symbols
a Particle radius
A Projected area of particle(s) illuminated by incident light
c Numerical particle concentration
n
E Extinction coefficient
I(�) Angular intensity distribution of light scattered by a particle
I(r) Light flux scattered by a particle at a specific solid angle
I Scattered light polarized in a direction perpendicular to the incident light beam
I Scattered ight polarized in a direction parallel to the incident light beam
k Imaginary (absorption) part of a particle refractive index
p
l Beam path through a sensing zone
n Refractive index of a particle, relative to that of the suspension medium
n Real part of the refractive index of the suspension medium
m
n Real part of the refractive index of the particle
p
x Particle diameter, in micrometres. Unless otherwise specified, the equivalent optical diameter is reported
y Ratio of scattered or transmitted light flux to incident light flux
� The term of particle projected area divided by the illumination wavelength, 2�A/�
� Scattering angle with respect to forward direction in degrees. The scattering angle may consist of a
significantly large solid angle, but is typically defined as the centre angle of the light collection system with
respect to the centre line of the illumination source
� Wavelength of the illumination source, in nanometres. The illumination source may emit light at a single
wavelength or over a broad range of wavelengths
4 Light interaction principles
4.1 Introduction
A brief summary of the parameters affecting light interaction with single-particles is presented in this clause. Further
details are provided in annex A. In single-particle light interaction devices, the output data are affected by
illumination wavelength and intensity, illumination source and collection optics configurations, as well as light
collection and capabilities of the data handling system. Particle and suspension fluid physical properties affect
response, as well. The particle size, shape, and orientation within the sensing zone may also affect the response.
The relative refractive index of the particle in the suspension fluid also affects the response.
4.2 Light scattering
Most particles measured by light-scattering will be in the size range from approximately 50 nm to 100µm. When
light interacts with the particle, the scattered light flux varies roughly with the projected area of the particle for
particles with radius significantly larger than the light wavelength. For smaller particles, the variation of the
scattered light flux changes with particle radius, increasing to the sixth power as particle size decreases to
approximately 0,2µm. A light-scattering system used for submicrometer particles will normally be used to measure
particles over a size range up to 50:1. A system that is used to measure particles larger than approximately 1µm
can measure over a size range of approximately 100:1. The limitations are connected with the linearity of electronic
data processing systems over wide ranges (e.g. 5� 10 ) and the need to ensure that the smallest signal that is
processed is larger than the electronic and optical background noise level.
NOTE Further details on the operation of light-scattering instruments for counting and/or sizing particles can be obtained
[3]
from the reference in the bibliography.
4 © ISO 2000 – All rights reserved

4.2.1 Physical principles
Measurement of scattered light from fluidborne particles is carried out by observing the scattered light from the
particle at a specific solid angle that is defined by a particular instrument configuration. The particle(s) within the
sensing zone of the instrument may be present within a known volume of fluid moved through the instrument or
may be moving with “normal” fluid flow through a defined known sensing zone established within the instrument. In
the first case, the particle concentration per unit fluid volume is defined; in the second case, the particle flux per unit
area through which particles are moving is defined on a time basis. The instruments which report the particle
concentration are normally used to characterize particle size distribution and concentration in fluids which are
moving under specific conditions at pressures ranging from near ambient to approximately 500 kPa. Instruments
defining particle flux are often used when flow is random or at pressures from approximately 1 kPa to ambient.
4.2.2 Optical system designs
Typical optical system bases for single-particle light-scattering instruments are shown in Figure 1. The
configurations shown here describe essentially every optical design of the light-scattering instrument used for this
purpose. The original designs, laid out in 1965, used incandescent-filament illumination sources, lens and aperture
systems to define sensing zones. A summary of single-particle light-scattering instruments designed for aerosol
studies was shown recently. Current optical systems use either gas or diode-laser illumination that may not require
the same type of beam-shaping systems. Even so, the basic optical system designs for light collection are still
followed. The choice for selection is based upon the particle size range of concern, available components,
construction funds, and the environments in which particle measurements are to be made. Essentially, the same
optical design base can be used for measurements in gas or in liquid suspension. The major differences are in the
fluid control systems used for the two applications. The problems of defining the edges of the sensing zones are
greater when working with liquid systems. Larger particles are more frequently measured in liquid than in gas and a
small portion of a liquid-borne large particle may move through an optically defined sensing zone, scattering as
much light as a small particle entirely within the sensing zone. Procedures for minimizing this effect and other
problem areas will be discussed in ISO 13323-2 and ISO 13323-3.
[4]
NOTE Further information on the optical design of airborne-particle counting systems can be obtained from reference in
the bibliography.
In general, particle counters using monochromatic light sources and forward-scattering systems with a small solid
angle produce a multi-valued response of scattered light flux as a function of particle size. The response will
increase and decrease with particle size over some portions of the instrument dynamic range. Particle counters
with polychromatic light, and especially those with scattering systems with a large solid angle, produce the
desirable response where scattered light flux does not increase and decrease as the particle size increases, but the
instrument sensitivity for small particle measurement may be decreased unless illumination intensity is increased
and the design of the optical and electronic systems minimizes background noise levels. In this connection, laser
illumination systems can generate light flux intensity levels of several watts in the sensing zone. The use of light-
collection optical systems with a large angle here will also minimize multi-valued response.
Key
1 Light
2 Aperture
3 Traps
4 Aerosol
5 Collection
Figure 1 — Basic optical designs for light-scatt
...