This method is applicable to the determination of particles in electronic grade hydrogen, nitrogen, oxygen, argon, and helium, and is also applicable to the determination of particles in ordinary hydrogen, nitrogen, oxygen, argon, helium and other non-corrosive gases. SJ 2798-1987 Determination of particles in electronic grade gases - Light scattering method SJ2798-1987 standard download decompression password: www.bzxz.net
This method is applicable to the determination of particles in electronic grade hydrogen, nitrogen, oxygen, argon, and helium, and is also applicable to the determination of particles in ordinary hydrogen, nitrogen, oxygen, argon, helium and other non-corrosive gases.

Standard of the Ministry of Electronic Industry of the People's Republic of China SJ2798-87
Method for determination of particles and trace impurities in electronic grade gases
Published on May 18, 1987wwW.bzxz.Net
Approved by the Ministry of Electronic Industry of the People's Republic of China and implemented on January 1, 1988
Method for determination of particles in electronic grade gases of the Ministry of Electronic Industry of the People's Republic of China
Light scattering method
SJ2798-87
This method is applicable to the determination of particles in electronic grade hydrogen, nitrogen, oxygen, and oxygen, and is also applicable to the determination of particles in ordinary hydrogen, nitrogen, oxygen, hydrogen, ammonia and other non-corrosive gases. 1. Terminology and Principle of the Method
1.1 Terminology
1.1.1 Particle size---The nominal length size of a particle material measured by a certain determination method. This standard refers to the comprehensive effect obtained by making an equivalent comparison of the scattered light intensity with the polystyrene standard particles, representing the range of individual sizes, in units of m. 1.1.2 Particle size refers to the number of particles larger than a specific particle size contained in a unit volume of gas. This standard refers to the number of particles with a particle size equal to or greater than 0.5 μm contained in a unit volume of gas, in units of pieces/liter. 1.2 Principle of the method
The scattered light intensity of a single particle within a certain range is proportional to the square of its particle size. The light forms a fine beam through a focusing lens and a slit, and is projected into a bright and uniform photosensitive area in the scattering cavity. When the gas containing particles passes through the scattering cavity and the sensitive measurement area, the particles reflect the incident light, and the scattered light is received by the absorption lens group and converted into an electrical pulse signal proportional to the scattered light intensity through the photomultiplier tube. The electrical pulse signal is processed and finally displayed on the counter to display the particles of various sizes and the number of particles. When the sampling flow rate and sampling time are fixed, the total number of particles larger than this particle size in the fixed volume can be calculated and converted into the value of the particles. 2 Instruments and equipment
2.1 The instruments and equipment of the measurement system should consist of a pressure reducing regulating valve, a buffer bottle, a light scattering particle counter and connecting pipes. As shown in Figure 1:
Pull-down counter
Particle measurement system device
Pressure reducing valve
Measured gas
2.2 Pressure reducing regulating valve, if the gas detection port already has a pressure reducing regulating valve, it can be no longer installed. Otherwise, it should be specially installed to ensure that there is a stable low pressure in the buffer bottle. 2.3 Buffer bottles use 2-51 glass bottles, which must be cleaned before use. 2.4 Connection channels should use pipes with smooth and clean inner walls, no dust, no droplets, and no gas, such as tetrafluoroethylene, vinyl hoses or stainless steel pipes and copper pipes with polished inner walls. The connecting pipes should be as short as possible. 2.5 The light scattering particle counter consists of three parts: gas circuit system, optical system and circuit system. 2.5.1 The gas circuit system consists of a sampling pump, a flow control valve, a high-efficiency filter, a buffer basin, a scattering air, a gas jacket and a gas pipeline. When a certain flow of the measured gas is drawn from the sampling port and is surrounded by the clean air jacket. When passing through the sensitive measurement area, the particles in the measured gas should not spread around and all be detected. The gas system should be airtight to prevent external particles from invading. The gas system should ensure the stability of the sampling flow rate. The general flow rate is 500ml/min. Within 1 hour, the flow rate should not exceed 2% over time.
2.5.2 The optical system includes an incandescent lamp, a condensing lens, a slit, a receiving lens group, a projection lens group, a nozzle lens, a photomultiplier tube, a light guide, a shielding disc, a chopper motor, etc. As shown in Figure 2. 2
Solution
$J2798-87
System Scattering Optical System
SJ2798-87
The light emitted by the incandescent lamp is formed into a sensitive measurement area of ​​illuminance by the condensing lens, the slit, and the projection lens. The scattered light of the particles passing through the sensitive measurement area is illuminated on the photomultiplier tube by the chopper lens, the slit, and the nozzle lens. The light guide is shielded from light, and the chopper motor produces an intermittent light beam. The optical system for collecting light is supplied with pulsed scattered light, and the working state of this part is adjusted to keep the particle size selection ability of the particle counter stable. The structure of the entire optical system does not cause deformation under mechanical impact and other vibrations. The voltage of the light source should use a regulated power supply. 2.5.3 The circuit system should be composed of a power supply, a photoelectric conversion part, a particle signal amplification measurement part and a display part. 2.5.3.1 The power supply of the instrument should use a regulated circuit with high voltage stability and can work normally when the external voltage fluctuates by 10%.
2.5.3.2 The function of the photoelectric conversion part is to convert the scattered light focused by the optical system into an electrical signal corresponding to the light intensity. Generally, a photoelectric amplification tube is used as the photoelectric conversion part. 2.5.3,3 The particle signal amplification measurement part is to process, compare and identify the particle signals of 10, 3μm, 1um, 1μm, etc. respectively, and then send them to the display part. 2.5.3.4 When the display part is in the form of a counter, it is composed of a counter that accumulates the number of particles with a large selected particle size or a display that indicates the count value and particle size. The display part with a time control circuit can select different sampling times. 3 Test conditions
3.1 Ambient temperature 5~40℃;
3.2 Ambient relative humidity is less than 80%;
3.3 Power supply voltage change is less than ±10% of the reference value: 3.4 The magnetic field strength around the instrument is less than 397A/m3.5 The vibration of the instrument workbench is less than 5m/S2;
3,5 The measured gas should not contain harmful impurities such as oil, corrosive gas, etc. 4 Measurement steps
4.1 Preparation before measurement
4.1.1 Connect the measurement system as shown in Figure 1, open the regulating valve, and ventilate for a certain period of time to allow the particles in the measurement system to reach a nearly balanced state.
4.1.2 Turn on the power supply and allow the particle counter to go through a specified preheating time to stabilize the particle counter. 4.1.3 Check whether the sampling tube and the self-cleaning tube are closed and intact, press the sampling display switch, and adjust the sampling flow to make the sampling flow rate the specified value.
4.1.4 Press the inspection display switch to calibrate the instrument and adjust it to pass. 4.1.5 Press the sampling display switch again. After sufficient self-cleaning, all counter counts should be zero. 4.2 Measurement
4.2.1 Turn on the measurement system, adjust the sampling valve, and control the sampling flow rate to the specified value. Adjust the pressure reducing regulating valve to maintain a stable lower positive pressure in the buffer bottle. 4.2.2 In order to obtain higher measurement accuracy, increase the sampling volume of the measurement count. Generally, the sampling volume of each measurement count should be at least 11.
4.2.3 The sampling time is calculated as follows:
Where:
SJ2798-87
- sampling time, unit, imirit
Q- sampling volume, unit, },
R——sampling flow rate, unit, 1/min. 4.2.4 To ensure that the statistical error is less than ±10% (the statistical error varies with the inverse of the square root of the number of particles), the sample should contain at least 100 particles larger than 0.5μm. However, when 100 particles larger than 0.5μm cannot actually be obtained, the particle size can be considered to be low. In order to improve the statistical accuracy of a large number of counts, the measurement must be repeated more than three times, and the average of three consecutive readings with similar readings is taken.
5 Calculation
Calculate the particle size according to the following formula:
P particle size, unit, liter:
N·average number of displayed particles, unit, pieces. R sampling flow rate, unit, 1/mint
t---sampling time, unit, min.
6 Accuracy and precision
In order to ensure that the statistical error is less than 10%, at least 100 particles larger than 0.5μm should be counted. The statistical error varies with the reciprocal of the square root of the number of particles.
7 Test report
The test report should include the following:
Test point
Test gas name;
Test date:
Tester's signature:
Model of dust particle counter used;
Sampling flow rate:
Test count sampling volume:
Counted particle size:
Problems encountered during the test
Particle size, unit is pieces/liter.
8 Precautions
8.1 The particle counter must have a factory certificate. When necessary, the particle size selection accuracy and particle counting accuracy of the particle counter should be calibrated by the relevant units.
日.2 When the particle counter is working, the membrane flowmeter measures the flow rate of the measured gas entering the sampling port, and adjusts the flow rate or calibrates the flowmeter. Within 1 hour, when the error of two consecutive measurements does not exceed 2%, take the average value as the correction value.
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There are different colored marks at the sampling flow rates of various gases corresponding to the particle counter. B.3 Maintain a stable, low positive pressure in the buffer bottle. It is important to ensure accurate testing. If the pressure is too high, not only the flow rate will be inaccurate, but also damage the particle counter; if the pressure is too low, it is easy to form a negative pressure, which makes the test data higher. Additional Notes
This standard was proposed by the Clean Technology Society of the China Electronics Society. It was sponsored by the Standardization Institute of the Ministry of Electronics Industry. This standard was drafted and revised by Zhou Dinghua, Du Junying of Beijing Semiconductor Device Testing Center, and Zhao Changchun of the Standardization Institute of the Ministry of Electronics Industry.
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