1、 g49g50g3g38g50g51g60g44g49g42g3g58g44g55g43g50g56g55g3g37g54g44g3g51g40g53g48g44g54g54g44g50g49g3g40g59g38g40g51g55g3g36g54g3g51g40g53g48g44g55g55g40g39g3g37g60g3g38g50g51g60g53g44g42g43g55g3g47g36g58Single particle light interaction methods Part 2: Light scattering liquid-borne particle counterICS
2、 19.120Determination of particle size distribution BRITISH STANDARDBS ISO 21501-2:2007BS ISO 21501-2:2007This British Standard was published under the authority of the Standards Policy and Strategy Committee on 29 June 2007 BSI 2007ISBN 978 0 580 52913 9Amendments issued since publicationAmd. No. Da
3、te Commentsrequest to its secretary.This publication does not purport to include all the necessary provisions of a contract. Users are responsible for its correct application.Compliance with a British Standard cannot confer immunity from legal obligations.National forewordThis British Standard was p
4、ublished by BSI. It is the UK implementation of ISO 21501-2:2007. Together with BS ISO 21501-3:2007 and BS ISO 21501-4:2007, it will supersede BS ISO 13323-1:2000 which is withdrawn.The UK participation in its preparation was entrusted to Technical Committee LBI/37, Sieves, screens and particle sizi
5、ng.A list of organizations represented on this committee can be obtained on Reference numberISO 21501-2:2007(E)INTERNATIONAL STANDARD ISO21501-2First edition2007-05-15Determination of particle size distribution Single particle light interaction methods Part 2: Light scattering liquid-borne particle
6、counter Dtermination de la distribution granulomtrique Mthodes dinteraction lumineuse de particules uniques Partie 2: Compteur de particules en suspension dans un liquide en lumire disperse BS ISO 21501-2:2007ii iiiContents Page Foreword iv Introduction v 1 Scope . 1 2 Terms and definitions. 2 3 Req
7、uirements 2 3.1 Size calibration 2 3.2 Verification of size setting . 2 3.3 Counting efficiency. 2 3.4 Size resolution 2 3.5 False count rate 3 3.6 Maximum particle number concentration 3 3.7 Sampling flow rate 3 3.8 Sampling time . 3 3.9 Sampling volume 3 3.10 Calibration interval . 3 3.11 Test rep
8、ort . 3 4 Test method. 4 4.1 Size calibration 4 4.2 Verification of size setting . 6 4.3 Counting efficiency. 6 4.4 Size resolution 6 4.5 False count rate 7 4.6 Maximum particle number concentration 7 4.7 Sampling flow rate 7 4.8 Sampling time . 8 4.9 Sampling volume 8 4.10 Calibration . 8 Annex A (
9、informative) Uncertainty of particle size calibration 9 Annex B (informative) Counting efficiency 11 Annex C (informative) Size resolution 12 Annex D (informative) False count rate 13 Bibliography . 15 BS ISO 21501-2:2007iv Foreword ISO (the International Organization for Standardization) is a world
10、wide 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 t
11、hat 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
12、 accordance with the rules given in the ISO/IEC Directives, Part 2. The main task of technical committees is to prepare International Standards. Draft International Standards adopted by the technical committees are circulated to the member bodies for voting. Publication as an International Standard
13、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 document may be the subject of patent rights. ISO shall not be held responsible for identifying any or all such patent rights. ISO 21501-2 was prepared by T
14、echnical Committee ISO/TC 24, Sieves, sieving and other sizing methods, Subcommittee SC 4, Sizing by methods other than sieving. This first edition of ISO 21501-2, together with ISO 21501-3 and ISO 21501-4, cancels and replaces ISO 13323-1:2000, which has been technically revised. ISO 21501 consists
15、 of the following parts, under the general title Determination of particle size distribution Single particle light interaction methods: Part 2: Light scattering liquid-borne particle counter Part 3: Light extinction liquid-borne particle counter Part 4: Light scattering airborne particle counter for
16、 clean spaces The following part is under preparation: Part 1: Light scattering aerosol spectrometer BS ISO 21501-2:2007vIntroduction Monitoring particle contamination levels is required in various fields, e.g. in the electronic industry, in the pharmaceutical industry, in the manufacturing of preci
17、sion machines and in medical operations. Particle counters are useful instruments for monitoring particle contamination in liquid. The purpose of this part of ISO 21501 is to provide a calibration procedure and verification method for particle counters, so as to minimize the inaccuracy in the measur
18、ement result by a counter, as well as the differences in the results measured by different instruments. BS ISO 21501-2:2007blank1Determination of particle size distribution Single particle light interaction methods Part 2: Light scattering liquid-borne particle counter 1 Scope This part of ISO 21501
19、 describes a calibration and verification method for a light scattering liquid-borne particle counter (LSLPC), which is used to measure the size and particle number concentration of particles suspended in liquid. The light scattering method described in this part of ISO 21501 is based on single part
20、icle measurements. The typical size range of particles measured by this method is between 0,1 m and 10 m in particle size. Instruments that conform to this part of ISO 21501 are used for the evaluation of the cleanliness of pure water and chemicals, as well as the measurement of number and size dist
21、ribution of particles in various liquids. The measured particle size using the LSLPC depends on the refractive index of particles and medium; therefore the measured particle size is equivalent to the calibration particles in pure water. The following are within the scope of this part of ISO 21501: s
22、ize calibration; verification of size setting; counting efficiency; size resolution; false count rate; maximum particle number concentration; sampling flow rate; sampling time; sampling volume; calibration interval; test report. BS ISO 21501-2:20072 2 Terms and definitions For the purposes of this d
23、ocument, the following terms and definitions apply. 2.1 calibration particle mono-disperse spherical particle with a known mean particle size, e.g. polystyrene latex (PSL) particle, that is traceable to an international standard of length, and where the standard uncertainty of the mean particle size
24、 is equal to or less than 2,5 % NOTE The refractive index of calibration particles is close to 1,59 at a wavelength of 589 nm (sodium D line). 2.2 counting efficiency ratio of the measured result of a light scattering liquid-borne particle counter (LSLPC) to that of a reference instrument using the
25、same sample 2.3 particle counter instrument that counts the number of particles and measures their size using the light scattering method or the light extinction method 2.4 pulse height analyser PHA instrument that analyses the distribution of pulse heights 2.5 size resolution measure of the ability
26、 of an instrument to distinguish between particles of different sizes 3 Requirements 3.1 Size calibration The recommended procedure for the size calibration is described in 4.1. 3.2 Verification of size setting The error in the detectable minimum particle size and other sizes specified by the manufa
27、cturer of an LSLPC shall be equal to or less than 15 % when the test is carried out by the method described in 4.2. 3.3 Counting efficiency The counting efficiency shall be (50 30) % for calibration particles with a size close to the minimum detectable size, and it shall be (100 30) % for calibratio
28、n particles with the particle size of 1,5 times to 3 times larger than the minimum detectable particle size. 3.4 Size resolution The size resolution shall be equal to or less than 10 % for calibration particles of a size specified by the manufacturer. BS ISO 21501-2:200733.5 False count rate The fal
29、se count rate is determined by measuring the particle number concentration in the unit of counts per litre at the minimum reported size range when sampling pure water. 3.6 Maximum particle number concentration The maximum measurable particle number concentration shall be specified by the manufacture
30、r. The coincidence loss at the maximum particle number concentration of an LSLPC shall be equal to or less than 10 %. NOTE When the particle number concentration is higher than the maximum particle number concentration, the number of uncounted particles increases because of an enhanced probability o
31、f multiple particles existing in the sensing volume (coincidence error) and/or saturation of the electronic system. 3.7 Sampling flow rate The standard uncertainty of the sampling flow rate shall be specified by the manufacturer. The user shall check that the sampling flow rate is within the range s
32、pecified by the manufacturer. 3.8 Sampling time The standard uncertainty in the duration of sampling time shall be equal to or less than 1 % of the preset value. If the LSLPC does not have a sampling time control system, this subclause does not apply. 3.9 Sampling volume The standard uncertainty of
33、sampling volume shall be equal to or less than 5 % of the preset value. This subclause does not apply when the LSLPC is not equipped with a sampling system. 3.10 Calibration interval It is recommended that the calibration interval of an LSLPC be one year or less. 3.11 Test report The following minim
34、um information shall be recorded: a) date of calibration; b) calibration particle sizes; c) flow rate; d) size resolution (with the particle size used); e) counting efficiency; f) voltage limit or channel of an internal pulse height analyser (PHA). BS ISO 21501-2:20074 4 Test method 4.1 Size calibra
35、tion When calibrating an LSLPC with calibration particles of known size, the median voltage (or internal PHA channel), corresponds to the particle size (see Figure 1). The median voltage (or internal PHA channel) should be determined by using a particle counter with variable voltage limit (or intern
36、al PHA channel) settings. The median voltage (or internal PHA channel) is the voltage (or internal PHA channel) that equally divides the total number of pulses counted. When a particle counter with variable voltage limit settings is not available, a PHA can be used in place of the counter. Key X pul
37、se height voltage (or channel) Y density 1 pulse height distribution with PSL particles Vllower voltage limit Vmmedian voltage Vuupper voltage limit Figure 1 Pulse height distribution of PSL particle signals When noise signals appear as if there are many small particles in the sample, the median vol
38、tage (or internal PHA channel) shall be determined by discarding the pulses due to “false particles” see Figure 2 a). The discarding should only be done when the density at the peak due to real particles is more than twice the density at the valley that separates it from the pulses due to “false par
39、ticles” see Figure 2 b). In this case, Vuis the voltage greater than the median voltage, Vm, where the density is the same as Vl. The median is calculated using only the population between the voltage limits Vland Vu. BS ISO 21501-2:20075a) b) Key X pulse height voltage (or channel) Y density 1 puls
40、e height distribution with PSL particles 2 noise (false particles, small particles and/or optical, electrical noise) Vllower voltage limit Vmmedian voltage Vuupper voltage limit Figure 2 Pulse height distribution of PSL particle signals with noise The voltages of channels corresponding to particle s
41、ize should be determined in accordance with the calibration curve provided by the manufacturer (see Figure 3). Key X particle size Y median value of calibration particles 1 calibration curve Vm,1median voltage corresponding to particle size xm,1Vm,2median voltage corresponding to particle size xm,2V
42、m,3median voltage corresponding to particle size xm,3Figure 3 Calibration curve NOTE When the median voltage is determined by using an external PHA, the uncertainty in the voltage of PHA and the voltage uncertainty of the LSLPC are included in setting the voltage limits of the LSLPC (see Annex A). B
43、S ISO 21501-2:20076 4.2 Verification of size setting Obtain response voltages (or internal PHA channel) in accordance with the test method given in 4.1, using at least three kinds of calibration particles that span most of the reported size range, xr, of the LSLPC. Determine the calibration curve fr
44、om these response voltages (or internal PHA channel) and the calibration particle sizes. Calculate the corresponding particle size, xs, from the voltage (or internal PHA channel) setting of the LSLPC using the calibration curve. Obtain the size setting error, , by means of Equation (1) below, and ex
45、amine whether it satisfies the requirement given in 3.2. srr(%) 100xxx=% (1) where is the size setting error, in %; xris the reported size range, in m; xsis the calculated particle size, in m. 4.3 Counting efficiency To test the counting efficiency of the LSLPC, use calibration particles with two si
46、zes: one that is close to the minimum detectable reported size range, and another that is 1,5 times to 3 times larger than the minimum detectable size. Measure the particle number concentration of both particles with the LSLPC under test and either a microscopic method or a calibrated LSLPC as a ref
47、erence instrument. The counting efficiency is the ratio of the particle number concentration measured by the LSLPC under test and the particle number concentration measured by the reference instrument (see Annex B). 4.4 Size resolution Determine the median voltage (or channel), Vm, using monodispers
48、e calibration particles, as shown in Figure 4. The lower voltage limit, Vl, and upper voltage limit, Vu, are defined as those corresponding to a density of 61 %. Using the calibration curve, determine the particle sizes corresponding to Vland Vu. Calculate the absolute value of the differences in pa
49、rticle size between PSL particle size and particle size corresponding to Vland Vu. The greater of these is the observed standard deviation, . Calculate the percentage of size resolution, R, of the LSLPC by Equation (2) below (see also Annex C). 22PP(%) 100Rx=% (2) where R is the size resolution, in %; is the observed standard deviation of LSLPC, in m; Pis the suppliers reported standard deviation of calibration particles, in m; xPis the particle size of the ca
