Standard Practice for Calibration of a Liquid-Borne Particle Counter Using an Optical System Based Upon Light Extinction

SCOPE
1.1 This practice covers procedures for calibrating and determining performance of an optical liquid-borne particle counter (LPC) which uses an optical system based upon light extinction measurement. This practice is directed towards determination of accuracy and resolution of the LPC for characterizing the size and number of particles, which have been passed into the sample inlet of the LPC. Consideration of inlet sampling efficiency is not part of this practice.
1.2 The procedures covered in this practice include those to measure sample volume and flow rate, zero count level, particle sizing and counting accuracy, particle sizing resolution, particle counting efficiency, and particle concentration limit.
1.3 The particle size parameter reported in this practice is the equivalent optical diameter based on projected area of calibration particles with known physical properties dispersed in liquid. The manufacturer normally specifies the minimum diameter that can be reported by an LPC; the dynamic range of the LPC being used determines the maximum diameter that can be reported for a single sample. Typical minimum reported diameters are approximately 2 ´m, and a typical dynamic range specification will be approximately from 50 to 1.
1.4 The counting rate capability of the LPC is limited by temporal coincidence of particles in the sensing volume of the LPC and by the saturation level or maximum counting rate capability of the electronic sizing and counting circuitry. Coincidence is defined as the simultaneous presence of more than one particle within the LPC optically defined sensing zone at any time. The coincidence limit is a statistical function of particle concentration in the sample and the sensing zone volume when particle size is insignificant in comparison to the sensing volume dimensions. This limitation may be modified by the presence of particles with dimension so large as to be a significant fraction of the sensing zone dimension. The saturation level rate of the electronic counting circuitry shall be specified by the manufacturer and is normally greater than the LPC recommended maximum counting rate for the particle concentrations used for any portion of this practice.
1.5 Calibration in accordance with all parts of this practice may not be required for routine field calibration of an LPC unless significant changes have occurred in operation of the LPC or major component repairs or replacements have been made. The LPC shall then be taken to a suitable metrology facility for complete calibration. Normal routine field calibration may determine sample flow rate, zero count level, and particle sizing accuracy. The specific LPC functions to be calibrated shall be determined on the basis of agreement between the purchaser and the user. The maximum time interval between calibrations shall be determined by agreement between the purchaser and the user, but shall not exceed twelve months, unless LPC stability for longer periods is verified by measurements in accordance with this practice.
1.6 This standard may involve hazardous materials, operation, and equipment. 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.

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NOTICE: This standard has either been superseded and replaced by a new version or discontinued.
Contact ASTM International (www.astm.org) for the latest information.
Designation: F 658 – 00 An American National Standard
Standard Practice for
Calibration of a Liquid-Borne Particle Counter Using an
Optical System Based Upon Light Extinction
This standard is issued under the fixed designation F 658; 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 (e) indicates an editorial change since the last revision or reapproval.
1. Scope saturation level rate of the electronic counting circuitry shall be
specified by the manufacturer and is normally greater than the
1.1 This practice covers procedures for calibrating and
LPC recommended maximum counting rate for the particle
determining performance of an optical liquid-borne particle
concentrations used for any portion of this practice.
counter (LPC) which uses an optical system based upon light
1.5 Calibration in accordance with all parts of this practice
extinction measurement. This practice is directed towards
may not be required for routine field calibration of an LPC
determination of accuracy and resolution of the LPC for
unless significant changes have occurred in operation of the
characterizing the size and number of particles, which have
LPC or major component repairs or replacements have been
been passed into the sample inlet of the LPC. Consideration of
made. The LPC shall then be taken to a suitable metrology
inlet sampling efficiency is not part of this practice.
facility for complete calibration. Normal routine field calibra-
1.2 The procedures covered in this practice include those to
tion may determine sample flow rate, zero count level, and
measure sample volume and flow rate, zero count level,
particle sizing accuracy. The specific LPC functions to be
particle sizing and counting accuracy, particle sizing resolu-
calibrated shall be determined on the basis of agreement
tion, particle counting efficiency, and particle concentration
between the purchaser and the user. The maximum time
limit.
interval between calibrations shall be determined by agreement
1.3 The particle size parameter reported in this practice is
between the purchaser and the user, but shall not exceed twelve
the equivalent optical diameter based on projected area of
months, unless LPC stability for longer periods is verified by
calibration particles with known physical properties dispersed
measurements in accordance with this practice.
in liquid. The manufacturer normally specifies the minimum
1.6 This standard may involve hazardous materials, opera-
diameter that can be reported by an LPC; the dynamic range of
tion, and equipment. This standard does not purport to address
the LPC being used determines the maximum diameter that can
all of the safety concerns, if any, associated with its use. It is
be reported for a single sample. Typical minimum reported
the responsibility of the user of this standard to establish
diameters are approximately 2 μm and a typical dynamic range
appropriate safety and health practices and determine the
specification will be approximately from 50 to 1.
applicability of regulatory limitations prior to use.
1.4 The counting rate capability of the LPC is limited by
temporal coincidence of particles in the sensing volume of the
2. Referenced Documents
LPC and by the saturation level or maximum counting rate
2.1 ASTM Standards:
capability of the electronic sizing and counting circuitry.
D 1193 Specification for Reagent Water
Coincidence is defined as the simultaneous presence of more
D 3195 Practice for Rotameter Calibration
than one particle within the LPC optically defined sensing zone
E 20 Practice for Particle Size Analysis of Particulate Sub-
at any time. The coincidence limit is a statistical function of
stances in the Range of 0.2 to 75 Micrometres by Optical
particle concentration in the sample and the sensing zone
Microscopy
volume when particle size is insignificant in comparison to the
2 2.2 Other Documents:
sensing volume dimensions . This limitation may be modified
ANSI/NCSL Z540-1-1994 Laboratories and Measuring and
by the presence of particles with dimension so large as to be a
3 Test Equipment—General Requirements
significant fraction of the sensing zone dimension . The
ISO 11171 Hydraulic Fluid Power—Calibration of Liquid
Automatic Particle Counters
This practice is under the jurisdiction of ASTM Committee E-29 on Particle
ANSI B93.20M-1972 Fluid Sample Containers—
and Spray Characterization and is the direct responsibility of Subcommittee E29.02
Qualifying and Cleaning Methods
on Non-Sieving Methods.
Current edition approved April 10, 2000. Published June 2000. Originally
published as F 658 – 99. Last previous edition F 658 – 99.
Jaenicke, R., “The Optical Particle Counter: Cross-Sensitivity and Coinci- Annual Book of ASTM Standards, Vol 11.01.
dence,” Journal of Aerosol Science, Vol 3, 1972, pp. 95-111. Annual Book of ASTM Standards, Vol 11.03.
3 6
Knapp, J. Z. and Abramson, L. R., “A New Coincidence Model for Single Discontinued; see 1994 Annual Book of ASTM Standards,Vol
Particle Counters. I Theory and Experimental Verification,” Journal of Parenteral Available from the American National Standards Institute, 11 W. 42nd St., 13th
Science and Technology, Vol 48, 1994, pp. 255-294. Floor, New York, NY 10036.
Copyright © ASTM, 100 Barr Harbor Drive, West Conshohocken, PA 19428-2959, United States.
F 658
3. Terminology typical lower size sensitivity of the LPC is approximately 2.5
μm and the largest size reported is approximately 50 μm. The
3.1 Definitions of Terms Specific to This Standard:
difference in size ranges for monodisperse and polydisperse
3.1.1 calibration—measurement, reporting, and adjustment
particle calibration results from the differences in physical
if required, of an instrument in comparison with a certified
properties for the two particle types. The effect on the dynamic
standard material or instrument of known adequate accuracy.
range limitation of the limited large particle concentration for
Primary calibration is carried out with a standard material with
the polydisperse material is discussed in 8.2.
characteristics that are directly traceable to a recognized
3.1.10 inlet flow—the sample flow that enters the LPC
standards agency. Secondary calibration is carried out using a
through the flow inlet. Flow rate is expressed as volume per
method recognized by a voluntary standards-producing agency,
unit time, at ambient temperature and pressure.
even if a reference material rather than a standard material is
3.1.11 lower sizing limit—the smallest particle size at which
used for the calibration.
the LPC is capable of measuring with counting efficiency of 50
3.1.2 calibration particles—two types of calibration par-
6 10 %.
ticles are used to calibrate the LPC. The size or size distribution
3.1.12 monodisperse—a particle size distribution with rela-
of the calibration particles shall be determined by procedures
tive standard deviation less than 5 %. Polystyrene latex (PSL)
traceable to a recognized standards laboratory. Monodisperse,
particles are commercially available with this property in
isotropic particles of known dimension and physical properties
particle sizes ranging from less than 2 μm to greater than 80
are used directly for size calibration. These are available in
mm.
diameters covering the operating range of most LPCs. When
3.1.13 particle size—for calibration, particle size is either
size calibration is carried out with polydisperse particles, the
the modal diameter of the monodisperse calibration particle
particle size distribution is specified over the size range of
suspension used for each size threshold definition or it is the
concern, the mass concentration of the polydisperse particles in
size associated with a specified cumulative particle population
the calibration suspension is known, and the reported particle
when a polydisperse particle suspension is used. For applica-
population data are used to establish a calibration. The cali-
tion purposes, particle size is the diameter of a reference
bration particles are described further in 4.2, 10.3, and 10.4
particle with known properties, which produces the same
3.1.3 calibration suspension—a suspension of calibration
response from the LPC as the particle being measured.
particles with a known particle size distribution dispersed in a
3.1.14 pulse height analyzer (PHA)—an electronic device
clean liquid. The mass concentration of the particles may be
for collecting and sorting electronic pulses by voltage level.
specified and the particle concentration in specific size ranges
The output is a histogram with 16 to 4096 levels, (referred to
can be determined from these data.
as “channels”). A PHA may be built into an LPC or may be
3.1.4 coincidence—the simultaneous presence of more than
connected to an LPC output test point. The PHA shall have at
one particle within the sensing volume of the instrument,
least 16 channels and shall be capable of defining the voltage
causing the instrument to report the combined signal from the
pulse level in any channel with 95 % accuracy.
several particles as arising from a single larger particle.
3.1.15 relative standard deviation—a measure of the width
3.1.5 concentration—number or mass of particles within a
of a particle size distribution data histogram. It is quantified in
specific size range or equal to and larger than a specific particle
terms of the ratio of the standard deviation of the distribution
size per unit volume of liquid at ambient temperature and
to the mean of the distribution. It is normally expressed as a
pressure.
percentage.
3.1.6 concentration limit—the upper concentration by num-
3.1.16 resolution—a measure of the ability of an LPC to
ber per unit volume of liquid specified by the LPC manufac-
differentiate between particles of nearly the same size; also, the
turer where the coincidence error is below 10 %. A maximum
range of sizes, which an LPC would report for a particular
concentration limit producing an error less than 10 % may be
particle if its size was determined repeatedly. It can be
chosen, as required.
quantified as the ratio of the difference between the reported
3.1.7 counting effıciency—the ratio, expressed as a percent-
and true relative standard deviations for a measured series of
age, of the reported particle concentration in a given size range
monodisperse particles.
to the actual concentration in the measured suspension.
3.1.17 sampled flow—the fluid, which passes through the
3.1.8 dilution ratio—when preparing particle suspensions to
sensing volume of an LPC. The sampled flow may be either a
define the particle concentration limit (see 4.6 and 10.7), the
portion of or the entire inlet flow. Sampled flow is expressed as
dilution ratio is the ratio of the volume of the undiluted
volume per unit time, at ambient temperature and pressure.
suspension plus particle-free diluent to the volume of the
3.1.18 saturation level—the maximum counting rate of the
undiluted suspension.
electronic circuitry at which accurate pulse amplitude sizing
3.1.9 dynamic range—the particle size range in which the
data are produced. The counting rate depends upon both the
LPC produces particle size data with both a lower and a upper
particle concentration and the sampled flow rate.
size boundary. The range may be expressed as a particle size
3.1.19 sensing volume—the portion of the illuminated vol-
ratio, when the lower size is known. When the LPC is
ume in the LPC through which the sample passes and from
calibrated with monodisperse calibration particles, the typical
which absorbed light signals are collected by the LPC photo-
lower size sensitivity of an LPC is 2 μm; the largest particle
detector.
size typically reported is approximately 125μm. When the LPC
is calibrated with a polydisperse calibration suspension, the 3.1.20 zero count rate—the maximum count indicated by an
F 658
LPC in a specified time period when the LPC is sampling tion particles. The LPC modal pulse amplitude response to the
liquid free of particles larger than the lower sizing limit of that calibration particle suspensions is recorded along with the
LPC. This is also referred to as“ false count rate” or “back-
standard deviation of the LPC pulse data. Refer to 10.3 for a
ground noise level.”
complete description of this procedure.
4.2.2 Particle Sizing Accuracy Based on Response to Poly-
4. Summary of Practice
disperse Particles With Known Particle Size Distribution—A
4.1 Inlet Sample Volume and Flow Rate—To report sampled
suspension of polydisperse calibration particles is prepared by
particle concentration accurately, it is necessary to define the
dispersing a known weight of these particles in a known
sample volume and to control the flow rate accurately. That
volume of clean liquid. Extreme care is required when remov-
flow rate may change if flow components in the LPC or in the
ing a sample of polydisperse particles from the container to
liquid feeding system are affected by long-term operation or
ensure that a truly representative sample is procured in such a
become plugged by deposition of particulate material. The
way that its removal does not change the size distribution of the
LPC flow is normally defined at a specific pressure and should
remaining material in the container. The liquid shall be chosen
not be changed during measurements. A calibrated volumetric
with viscosity and specific gravity sufficient to keep the largest
flow measurement device is required which operates with a
particle of concern suspended in the liquid for a time sufficient
pressure drop small enough so that the LPC flow control
for measurement. The particle size distribution data of these
system is not loaded to the point where flow is degraded. If a
calibration particles shall be characterized by a measurement
mass flowmeter is used, correction to volumetric flow may be
method traceable to a national or international standards
required when liquid of different density than that used for
development agency. A selected volume of suspension liquid is
calibration is being measured. The flow measurement device is
passed through the sensor LPC. That volume is selected so that
coupled to the LPC inlet and the LPC feeder sampling pump is
there will be a sufficient number of the largest particle for
operated. The flow indication on the calibration flowmeter is
which calibration data are required present in that volume of
recorded and compared with the collected sample volume over
suspension. The number of particles per selected volume of
the sample measurement time or with the LPC sample feeder
suspension with si
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