The dust particle counter is an important instrument widely used in the field of cleanliness. It is mainly used to assess the clean room cleanliness level. It can also be used to check the filter efficiency of the filter and the amount of dust generated by the clean fabric. The industries used include electronics factories, pharmaceutical companies, medical device factories, and testing laboratories. The dust particle counter uses the principle of light scattering to measure the number and particle size of dust particles in the air. The working principle (Fig. 1): the light from the light source is focused by the mirror group on the detection area, and the dust particle counter uses the sampling pump to sample the air. Pass through the area. When a dust particle (abbreviated as particle) passes, the incident light is scattered once, and an optical pulse signal is generated. After amplification and screening, the desired signal is screened and displayed by the counting system. The height of the electrical pulse signal reflects the particle. Size, the number of signals reflects the number of particles. The main technical indicator of concern is the size and number of particles.
The size of the particles can be traced to standard particles, usually using polystyrene plastic latex beads (PLS: Polymer Latex Suspensions), which can be traced by scanning electron microscopy. However, the number of particles is difficult to have a reliable traceability method. The particles detected by the dust particle counter are difficult to capture, and there is no effective way to count the number and cannot be weighed. Even though each step of sampling is performed very well, the count display of different dust particle counters will still vary greatly. The main reason is that there are differences in the design and performance of various dust particle counters. Therefore, the calibration of dust particle counters has been a hot and difficult point in research at home and abroad.
A large number of foreign literature [2-5] mentioned the concept of counting efficiency. The counting efficiency is the ratio of the number of particles displayed by the dust particle counter to the number of standard particles obtained by sampling the aerosol from the inlet of the dust particle counter. Instruments with a small measurable particle size < 0.2 μm are classified as Class A, and ≥ 0.2 μm are classified as Class B. Class A particle counters are condensed core counters or similar counters with not less than equivalent performance. Class A counters can be used to obtain the counting efficiency of class B counters. Specific indicators of counting efficiency: dust particle counters for small measurable particle sizes The down-counting efficiency should not be solved by the traceability problem of the sub-counter. It is only the acquiescence of everyone and it has not become a benchmark. The literature also mentions the particle size response voltage. This method requires a multi-channel pulse amplitude analyzer to be connected to the output of the dust particle counter to be tested (the output of the preamplifier or the input of the main amplifier). An experimental aerosol for standard particles of different particle sizes is generated by a standard particle generating device, pulse signals corresponding to different particle size files are analyzed, and a pulse frequency curve is determined to determine response voltages of different standard particles. It is also mentioned that the calibration is performed by a comparison method using a dust particle counter.
According to the traceability requirements of the dust particle counter, JJG547-88 "Dust Particle Counter" was established in 1988. The particle size distribution accuracy of the dust particle counter and the dispersion of monodisperse particle measurement were determined by using polydisperse standard particles. This procedure circumvents the direct determination of particle concentration, using the partial method, all of which are indirect values. In 2008, after years of efforts, the procedure was revised and changed to JJF1190-2008 "Dust Particle Counter" [7]. The main technical specifications of the specification include appearance requirements, insulation resistance, electrical strength, self-cleaning time, flow error, timing error, repeatability, particle size distribution error, particle concentration indication error, covering the basic performance of the measuring instrument, and also Taking into account factors such as the scientificity and operability of the verification work. The specification proposes to use standard particle generators to generate standard particle aerosols, with precision dust particle counters as the standard, to calibrate the indicators that have been evaded but extremely important: particle concentration indication error. The key to dust particle counter calibration is standard particle generators, precision dust particle counters, and data processing.
In the 1970s, China developed the first dust particle counter in China and began research on dust particle counters and calibration methods. In 1985, GB6167.1 ~ GB6167.2 - 85 "Dust Particle Counter Performance Experimental Method" was formulated and revised in 2009 [6]. This standard mainly refers to foreign related literature, and proposes counting efficiency, particle size response voltage and comparison method. It has a very positive significance for the product debugging and product quality improvement of the production enterprise, but it is not suitable for the metrological verification department to carry out the traceability of the value. (Firstly, the traceability of the metrological verification department is not allowed to disassemble the calibrated equipment).
The calibration of the dust particle counter does not establish a national standard (not seen abroad), so the calibration of the dust particle counter is very special and is very difficult. The implementation of the National Metrological Calibration Specification JJF1190-2008 "Dust Particle Counter" is beneficial to ensure the consistency of national value and to restrain the current market laissez-faire situation.
Processing high-throughput samples, intelligent reuse for large-capacity publishing, work surface: 200cm, 8 sample injection needles, 12 temperature-controlled incubation positions, 12 room temperature incubation positions, 32 plate storage positions, Sunrise microplate reader, HydroFlex plate washer, up to 512 specimens, sequential loading of samples, reagents, microplates Parallel loading of up to 6 plates for fast dispensing.
The automatic enzyme immunoassay analyzer is based on the principle that the enzyme and the substrate can produce a color reaction, the absorption lines of different substances have different characteristics, and strictly abide by the Lambert-Beer law, quantitative and qualitative analysis of substances. instrument. The method of analyzing the content of various enzymes such as antigen or antibody generally mainly adopts colorimetric method. In practice, spectrophotometry is the basic working principle of an automatic enzyme immunoassay analyzer. The light emitted by the light source lamp becomes a beam of monochromatic light after passing through a filter or a monochromator. The monochromatic light beam passes through the sample to be tested in the microtiter plate, and part of the monochromatic light beam is absorbed by the sample and reaches the photodetector. The intensity of the light signal projected on it is converted into the magnitude of the electrical signal by the photodetector. This electrical signal is processed by pre-amplification, logarithmic amplification, analog-to-digital conversion, etc., and then sent to the microprocessor for data processing and calculation, and the test results are output by the display and printer. The microprocessor completes the movement in the X and Y directions of the mechanical drive through the control circuit.
The automatic enzyme immunoassay analyzer adds the sample to the microwells of the pre-coated antigen or antibody microtiter plate, washes after the reaction, removes the unseparated ligand, then adds the enzyme isolate, after incubation, washes again , remove the unseparated compound, and then add the enzyme substrate, after the reaction, the colored final product is formed, and the stop solution is added to stop the reaction. The absorbance of each microwell of the microtiter plate is read by the wavelength that has been set by the spectrophotometer. The concentration value of the analyte in the sample is calculated by the absorbance value of the sample and the standard curve, so that the quantitative result can be obtained, or the absorbance of the sample is compared with that of the standard product, so that the positive or negative qualitative result can be obtained.
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