A dust particle counter with adjustable particle size channel and its measurement method

Abstract

The present invention provides a dust particle counter with adjustable particle size channel and a measuring method thereof, wherein the dust particle counter comprises a microprocessor, a signal acquisition device and a signal processing device, wherein the microprocessor is respectively connected to the signal acquisition device and the signal processing device, the signal acquisition device comprises a particle counting sensor, a flow sensor, a high efficiency filter and a vacuum pump, and the particle counting sensor, the flow sensor and the vacuum pump are respectively connected to the microprocessor; the signal processing device comprises a filtering circuit, a signal amplifying circuit, a primary voltage amplifying circuit, a secondary voltage amplifying circuit, a voltage reduction circuit, a voltage following circuit and n four-to-one analog switches, each of which is connected to a high-speed comparator, each of which is connected to a digital-to-analog conversion circuit, and each of which is connected to a pulse counting module of the microprocessor. The present invention can cover all channels of measurement on one device and reduce the equipment investment cost.

Description

Technical Field

[0001] The invention relates to the technical field of environmental monitoring, and in particular to a dust particle counter with adjustable particle diameter channel and a measuring method thereof. Background Art

[0002] Air particle pollution not only harms human health, but is also the main source of pollution in the production and processing of industries such as medicine, electronics, and aviation. For example, in the electronics industry and chip manufacturing industry, the deposition of tiny particles in the gas will cause poor electrical properties or even greater damage. In particular, in recent years, the chip line width has reached the micron and submicron level, which puts higher requirements on the air cleanliness in the factory. In addition, in modern medicine, drugs, and bioengineering, the "Good Manufacturing Practice for Pharmaceuticals GMP" formulated and implemented by countries around the world, including my country, also emphasizes the requirements for the cleanliness of particles in the air during the drug production process.

[0003] Currently, the main commercial instrument used for measuring air cleanliness is the dust particle counter, also called the optical particle counter (OPC). It uses the fact that particles in the air will scatter when exposed to light. The intensity of the scattered light has a certain linear relationship with the size of the particles. By measuring the amount and intensity of the scattered light, the concentration of particles in the air and the size of the particles can be effectively measured and statistically analyzed.

[0004] At present, laser particle counters can be divided into single-channel particle counters (only measuring one particle size), dual-channel particle counters (can test two particle sizes, such as Kanomax ultra-small particle counter 3950-00, whose particle size channels are 0.1μm and 0.3μm) and multi-channel particle counters (can test 6 particle sizes, such as Kanomax dust particle counter 3889, whose particle size channels are: 0.3, 0.5, 1.0, 3.0, 5.0, 10.0μm, TSI handheld laser particle counter 9306-03, whose particle size is: 0.3, 0.5, 0.7, 1.0, 2.0, 5.0 µm, PMS LASAIR II-110, whose particle size channels are: 0.1, 0.2, 0.3, 0.5, 1.0, 5.0µm, PMS Lasair III 5100, its particle size channels are 0.5, 1.0, 2.0, 5.0, 10.0, 25.0µm). According to JIS B9921 and ISO21501-4 standards, the particle size range of laser particle counters is from 0.1μm to 10μm and even extends to 25μm. However, according to the requirements of different applications, several standard dust particle counters with different particle size channels are needed to cover and meet the requirements of particle size channels, resulting in high costs, different measurement accuracy between different instruments, and effective calculation is required to unify the data, which is time-consuming and laborious. Summary of the invention

[0005] The technical problem to be solved by the present invention is to provide a dust particle counter with adjustable particle size channel and a measurement method thereof, so as to meet the requirement that one device covers all measurement channels, reduce equipment costs, and reduce calculation problems caused by accuracy differences between different instruments.

[0006] In a first aspect, the present invention provides a dust particle counter with adjustable particle size channel, comprising a microprocessor, a signal acquisition device and a signal processing device, wherein the microprocessor is connected to the signal acquisition device and the signal processing device respectively, and the signal acquisition device comprises a particle counting sensor, a flow sensor, a high efficiency filter and a vacuum pump, wherein the particle counting sensor, the flow sensor and the vacuum pump are connected to the microprocessor respectively;

[0007] The signal processing device includes a filtering circuit, a signal amplifying circuit, a primary voltage amplifying circuit, a secondary voltage amplifying circuit, a voltage reduction circuit, a voltage following circuit and n four-to-one analog switches. The filtering circuit is respectively connected to the particle counting sensor and the signal amplifying circuit, the signal amplifying circuit is respectively connected to the primary voltage amplifying circuit, the secondary voltage amplifying circuit, the voltage reduction circuit and the voltage following circuit, each of the four-to-one analog switches is connected to the primary voltage amplifying circuit, the secondary voltage amplifying circuit, the voltage reduction circuit and the voltage following circuit, and each of the four-to-one analog switches is connected to a high-speed comparator, each of the high-speed comparators is connected to a digital-to-analog conversion circuit, and each of the high-speed comparators is connected to a pulse counting module of a microprocessor.

[0008] Furthermore, the particle counting sensor includes an air path cavity, an optical path emitting unit, a silicon photodiode, a concave mirror, a convex lens, an aperture and a light trap. The optical path emitting unit is used to emit a parallel laser beam. The laser beam generates scattered light when passing through the particles in the air path cavity. The scattered light passes through the concave mirror, the convex lens, the aperture to the silicon photodiode in sequence. The silicon photodiode is used as a receiver to receive the scattered light. The light trap is used to absorb the laser beam. The optical path emitting unit includes a laser and a lens group. The laser beam of the laser emits a parallel laser beam after passing through the lens group.

[0009] Furthermore, the n is equal to the number of channels of the dust particle counter.

[0010] Furthermore, the signal amplifying circuit amplifies the voltage to between 0 and 12V.

[0011] Furthermore, the voltage amplification factor of the first-level voltage amplifier circuit is 5 times, the voltage amplification factor of the second-level voltage amplifier circuit is 10 times, and the voltage reduction factor of the voltage reduction circuit is 3 times.

[0012] Furthermore, the chip model of the high-speed comparator is LM339DG or TLV3501, the digital-to-analog conversion circuit uses a DAC7502 or TLV5610 chip, and the high-speed comparator uses the voltage signal output by the digital-to-analog conversion chip as a reference voltage of the high-speed comparator for comparison.

[0013] Furthermore, the chip model used by the four-select-one analog switch is CD4052 or TMUX6104.

[0014] Furthermore, the dust particle counter also includes a liquid crystal display unit, a printer, a storage unit and a communication interface, and the liquid crystal display unit, the printer, the storage unit and the communication interface are respectively connected to the microprocessor.

[0015] In a second aspect, the present invention provides a method for measuring a dust particle counter with an adjustable particle size channel, which requires providing a dust particle counter as described in the first aspect, and the method comprises the following steps:

[0016] Step 1: adjusting each channel parameter of the dust particle counter according to the measurement requirements, wherein the parameters include the particle size value;

[0017] Step 2, obtaining a voltage value corresponding to the particle size value according to the particle size spectrum, and connecting a four-choice analog switch to a primary voltage amplifier circuit, a secondary voltage amplifier circuit, a voltage reduction circuit or a voltage follower circuit according to the voltage value;

[0018] Step 3, starting the signal acquisition device to absorb the sample gas into the particle counting sensor, and when the particle counting sensor receives the scattered light of the particles, it generates a pulse signal and outputs it to the signal processing device;

[0019] Step 4: The pulse signal is filtered and amplified by a filtering circuit and a signal amplifying circuit;

[0020] Step 5, processing the pulse signal according to the circuit connected by the four-to-one analog switch, and outputting the processed pulse signal to the high-speed comparator;

[0021] Step 6: The high-speed comparator compares the voltage of the processed pulse signal with the reference voltage output by the digital-to-analog conversion chip. When the voltage of a pulse signal exceeds the reference voltage, a low level will be generated at the output of the high-speed comparator. Otherwise, the high-speed comparator maintains a high level.

[0022] Step 7: The microprocessor receives the standard pulse signal output by the high-speed comparator, accumulates and counts the interrupts generated by the falling edge of the pulse through the pulse counting module, and finally converts it into a concentration value of the number of particles.

[0023] Furthermore, the concentration value in step 7 is the number of particles per unit volume.

[0024] The advantages of the present invention are that any particle size channel of the dust particle counter of the present invention is a particle size adjustable channel, which can realize particle counting of multi-channel particle sizes of any composition such as single channel, dual channel, multi-channel, etc. The dust particle counter of the present invention can achieve full coverage of the particle size range of 0.1μm to 25μm, and only one device is needed to meet all particle size measurement requirements within the range, thereby reducing the equipment investment cost, and also avoiding the problem of large accuracy differences caused by the simultaneous use of multiple devices with different accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The present invention will be further described below in conjunction with embodiments with reference to the accompanying drawings.

[0026] Figure 1The present invention is a schematic diagram of the logical structure framework of a dust particle counter with adjustable particle size channel.

[0027] Figure 2 It is a schematic diagram of the structure of the signal processing device of the present invention.

[0028] Figure 3 It is a schematic diagram of the structure of the particle counting sensor of the present invention.

[0029] Figure 4 The figure is a schematic diagram of the circuit structure of the four-to-one analog switch of the present invention.

[0030] Figure 5 It is a structural schematic diagram of the primary voltage amplifier circuit of the present invention.

[0031] Figure 6 It is a structural schematic diagram of the secondary voltage amplifier circuit of the present invention.

[0032] Figure 7 It is a schematic diagram of the voltage follower circuit structure of the present invention.

[0033] Figure 8 It is a schematic diagram of the voltage reduction circuit structure of the present invention.

[0034] Fig. 9 Schematic diagram of the circuit structure of the high-speed comparator of the present invention.

[0035] Fig.10 The present invention is a flow chart of a measurement method of a dust particle counter with an adjustable particle size channel. DETAILED DESCRIPTION

[0036] See also Figures 1 to 9 , a dust particle counter with adjustable particle size channel of the present invention comprises a microprocessor, a signal acquisition device and a signal processing device, wherein the microprocessor is connected to the signal acquisition device and the signal processing device respectively, the signal acquisition device comprises a particle counting sensor, a flow sensor, a high efficiency filter and a vacuum pump, and the particle counting sensor, the flow sensor and the vacuum pump are connected to the microprocessor respectively;

[0037] The signal processing device includes a filtering circuit, a signal amplifying circuit, a primary voltage amplifying circuit, a secondary voltage amplifying circuit, a voltage reduction circuit, a voltage following circuit and n four-to-one analog switches. The filtering circuit is respectively connected to the particle counting sensor and the signal amplifying circuit, the signal amplifying circuit is respectively connected to the primary voltage amplifying circuit, the secondary voltage amplifying circuit, the voltage reduction circuit and the voltage following circuit, each of the four-to-one analog switches is connected to the primary voltage amplifying circuit, the secondary voltage amplifying circuit, the voltage reduction circuit and the voltage following circuit, and each of the four-to-one analog switches is connected to a high-speed comparator, each of the high-speed comparators is connected to a digital-to-analog conversion circuit (DAC circuit), and each of the high-speed comparators is connected to a pulse counting module of a microprocessor.

[0038] The microprocessor detects the flow rate of gas according to the flow sensor of the signal acquisition device, and adjusts the vacuum pump in real time to suck the gas into the particle counting sensor at a certain flow rate ((2.83±5%) L / min). When the detected gas passes through the particle counting sensor, a corresponding pulse signal is generated. The particle counting sensor sends the pulse signal to the signal processing device, and the filter circuit of the signal processing device removes noise from the pulse signal, and then amplifies the signal through the signal amplification circuit, selects the signal range to be measured by a four-to-one analog switch, and performs corresponding following, amplification or reduction on the pulse signal. After that, a high-speed comparator and a reference voltage are used to compare the signal and output a standard pulse signal to the pulse counting module of the microprocessor, which is received and counted by the pulse counting module, and finally calculated and output by the microprocessor.

[0039] The dust particle counter with adjustable particle size channel is also provided with a power supply connected with each of the above modules to supply power to each module.

[0040] The flow sensor in this embodiment can be built with a pressure sensor MPXV7007DP, and the pressure value of the pipeline and the atmospheric pressure value of the environment are differentially calculated, and the gas flow rate is calculated through the state equation of the fluid. The vacuum pump can be a rotary plate vacuum pump of the German Thomas model G 6 / 04 EB. The maximum sampling flow rate of the vacuum pump is 4L / min, and the maximum control voltage is 12V. The vacuum pump voltage is adjusted by combining the flow value with the PID algorithm to make the flow rate of the gas path constant. The default value is 2.83L / min. A high-efficiency filter is set at the front end of the pump to prevent large particles in the gas path from rubbing against the motor and extend the service life of the vacuum pump.

[0041] Better, such as Figure 2As shown, the particle counting sensor includes a gas path cavity 31, an optical path emitting unit 32, a silicon photodiode 33, a concave mirror 34, a convex lens 35, an aperture 36 and a light trap 37. The optical path emitting unit 32 is used to emit a parallel laser beam 38. The laser beam 38 passes through the particles 39 in the gas path cavity 31 to generate scattered light. The scattered light passes through the concave mirror 34, the convex lens 35, and the aperture 36 to the silicon photodiode 33 in sequence. The silicon photodiode is used as a receiver to receive the scattered light. The light trap is used to absorb the laser beam. The optical path emitting unit includes a laser 321 and a lens group 322. The laser beam of the laser 321 emits a parallel laser beam after passing through the lens group 322. In the figure, the x-axis is the laser irradiation direction, the y-axis is the gas flow direction, and the z-axis is the scattered light receiving direction. The three directions are perpendicular to each other. When in use, the vacuum pump controlled by the microprocessor can be used to suck the gas to be tested containing suspended particles into the air inlet of the gas path cavity. When the gas passes through the photosensitive area, the laser irradiates the particles and scatters. After the scattered light is focused by the reflector, the scattered light pulse signal is received by the detector at 90 degrees to the laser irradiation direction on the same horizontal plane. According to the number and strength of the pulse signal, the particle number concentration and particle size are measured. Among them, the optical path transmitting unit can use a red laser with a peak wavelength of 650nm produced by SANYO, and a high-precision silicon photodiode (with a photosensitive surface of 4mm*4mm) is used as the optical path scattered light signal receiving unit to improve the measurement accuracy. The scattered light signal of the particles irradiated by the laser is converted into an electrical signal. A set of gas path and scattered light optical path paths are designed, and the energy of the scattered light is evenly distributed on the photodiode using a beam focusing lens, which eliminates the measurement interference between particles of different particle sizes and realizes the simultaneous measurement of particles of different particle sizes.

[0042] Preferably, the n is equal to the number of channels of the dust particle counter, for example, n can be commonly used 1, 2, 6, etc.

[0043] Preferably, the signal amplification circuit amplifies the voltage to between 0 and 12 V. When the dust particle counter sensor receives scattered light from a particle, it generates a pulse signal, which is a narrow pulse signal with a pulse amplitude of hundreds of microvolts and a signal width of microseconds. Due to the limited signal output amplitude, large output impedance, and excessive signal-to-noise ratio, the original signal is first passed through a filter to remove the background noise of the particle counting sensor itself, and then the signal is passed through a high-power signal amplifier to adjust the voltage range of the pulse signal output to between 0 and 12 V.

[0044] Better, such as Figures 5 to 8As shown, the voltage amplification factor of the primary voltage amplifier circuit is 5 times, the voltage amplification factor of the secondary voltage amplifier circuit is 10 times, the primary voltage amplifier circuit and the secondary voltage amplifier circuit use the same circuit structure, and only the parameters need to be adjusted, and the voltage reduction factor of the voltage reduction circuit is 3 times. Since the voltage of the back-end analog circuit and the comparison circuit is 0~5V, in order to match the signal with the back-end circuit and increase the effective measurement range of the signal, the pulse signal is divided into the above four amplification and reduction circuits with different multiples for the analog switch to select according to needs.

[0045] Better, such as Fig. 9 As shown, the chip model of the high-speed comparator can be LM339DG or TLV3501, etc., the digital-to-analog conversion circuit (DAC circuit) can be DAC7502 or TLV5610 chip, etc., the high-speed comparator uses the voltage signal output by the digital-to-analog conversion chip as the reference voltage of the high-speed comparator for comparison. When the voltage of a pulse signal exceeds the reference voltage, a low level will be generated at the output end of the high-speed comparator. When it is lower than the reference voltage, the high-speed comparator maintains a high level. Therefore, the irregular analog pulse signal can be rectified into a standard pulse signal through the high-speed comparator, and the standard pulse signal is connected to the pulse counting module of the microprocessor.

[0046] Preferably, the chip model of the four-to-one analog switch can be CD4052 or TMUX6104. The four original signals after amplification, following and reduction are respectively connected to the four-to-one analog switch, and the signal path to be processed is selected by the analog switch. In order to simultaneously meet the requirements of the 0~12V voltage range of the front end and the 0~5V voltage range of the back end, the present invention designs a four-to-one analog switch to appropriately amplify and reduce the voltage to improve the calculation accuracy. Since the voltage values ​​corresponding to particles of different particle sizes are different, for example, the particle size to be measured is 0.3μm, and its corresponding voltage is 0.08V. You can choose a primary voltage amplifier circuit to amplify the original pulse signal 10 times. Then, after amplification 10 times, its voltage is 0.8V; if the voltage corresponding to a 1.0 particle is 0.49, you can choose to connect a secondary voltage amplifier circuit. After amplifying it 5 times, the output voltage is 2.45V. If the voltage does not need to be amplified or reduced, you can choose to connect to a voltage follower circuit. For example, the voltage corresponding to a 10μm particle is 6V, and its voltage can be reduced to 2V by connecting a voltage reduction circuit.

[0047] Preferably, the dust particle counter also includes a liquid crystal display unit, a printer, a storage unit and a communication interface, and the liquid crystal display unit, printer, storage unit and communication interface are respectively connected to the microprocessor, and the particle concentration value is displayed, printed, stored and transmitted through the microprocessor.

[0048] See also Figures 1 to 10 The present invention provides a method for measuring a dust particle counter with an adjustable particle size channel, which requires providing the dust particle counter as described above, and the method comprises the following steps:

[0049] Step 1: adjusting each channel parameter of the dust particle counter according to the measurement requirements, wherein the parameters include the particle size value;

[0050] Step 2, obtaining a voltage value corresponding to the particle size value according to the particle size spectrum, and connecting a four-choice analog switch to a primary voltage amplifier circuit, a secondary voltage amplifier circuit, a voltage reduction circuit or a voltage follower circuit according to the voltage value;

[0051] Step 3, starting the signal acquisition device to absorb the sample gas into the particle counting sensor, and when the particle counting sensor receives the scattered light of the particles, it generates a pulse signal and outputs it to the signal processing device;

[0052] Step 4: The pulse signal is filtered and amplified by a filtering circuit and a signal amplifying circuit;

[0053] Step 5, processing the pulse signal according to the circuit connected by the four-to-one analog switch, and outputting the processed pulse signal to the high-speed comparator;

[0054] Step 6: The high-speed comparator compares the voltage of the processed pulse signal with the reference voltage output by the digital-to-analog conversion chip. When the voltage of a pulse signal exceeds the reference voltage, a low level will be generated at the output of the high-speed comparator. Otherwise, the high-speed comparator maintains a high level.

[0055] Step 7: The microprocessor receives the standard pulse signal output by the high-speed comparator, accumulates and counts the interrupts generated by the falling edge of the pulse through the pulse counting module, and finally converts it into a concentration value of the number of particles.

[0056] Preferably, the concentration value in step 7 is the number of particles per unit volume, in units of particles per liter (or particles per 0.1 ft 3 , pieces / ft 3 ).

[0057] The signal acquisition device implemented by the present invention adopts an optical method and combines a signal processing circuit to measure the aerosol particle size. By designing 4 amplification, following, and reduction circuits with different multiples for selection, each channel can be adjusted. The present invention achieves full coverage of the particle size range of 0.1μm to 25μm in the same device. For example, when setting the flow channel, a dust particle counter with any combination of 6 channels can be realized, and the step of particle size selection is 0.1μm, for example: it can be combined into 0.1μm, 0.2μm, 0.3μm, 0.4μm, 0.5μm, 0.6μm, or 20.1μm, 21.3μm, 22.4μm, 23.1μm, 24.5μm, 25.0μm or other arbitrary combinations. The dust particle counter of the present invention meets the measurement needs of different environments, has high flexibility, and reduces equipment costs.

[0058] Although the specific implementation modes of the present invention are described above, those skilled in the art should understand that the specific implementation modes described are only illustrative and are not intended to limit the scope of the present invention. Equivalent modifications and changes made by those skilled in the art in accordance with the spirit of the present invention should be included in the scope of protection of the claims of the present invention.

Claims

1. A dust particle counter with adjustable particle size channel, comprising a microprocessor, a signal acquisition device and a signal processing device, wherein the microprocessor is connected to the signal acquisition device and the signal processing device respectively, and characterized in that: The signal acquisition device comprises a particle counting sensor, a flow sensor, a high efficiency filter and a vacuum pump, wherein the particle counting sensor, the flow sensor and the vacuum pump are respectively connected to a microprocessor; The signal processing device includes a filtering circuit, a signal amplifying circuit, a primary voltage amplifying circuit, a secondary voltage amplifying circuit, a voltage reduction circuit, a voltage following circuit and n four-to-one analog switches. The filtering circuit is respectively connected to the particle counting sensor and the signal amplifying circuit, the signal amplifying circuit is respectively connected to the primary voltage amplifying circuit, the secondary voltage amplifying circuit, the voltage reduction circuit and the voltage following circuit, each of the four-to-one analog switches is connected to the primary voltage amplifying circuit, the secondary voltage amplifying circuit, the voltage reduction circuit and the voltage following circuit, and each of the four-to-one analog switches is connected to a high-speed comparator, each of the high-speed comparators is connected to a digital-to-analog conversion circuit, and each of the high-speed comparators is connected to a pulse counting module of a microprocessor.

2. A dust particle counter with adjustable particle size channel as claimed in claim 1, characterized in that: The particle counting sensor includes an air path cavity, an optical path emitting unit, a silicon photodiode, a concave mirror, a convex lens, an aperture and a light trap. The optical path emitting unit is used to emit a parallel laser beam. The laser beam generates scattered light when passing through the particles in the air path cavity. The scattered light passes through the concave mirror, the convex lens, the aperture in sequence to the silicon photodiode. The silicon photodiode is used as a receiver to receive the scattered light. The light trap is used to absorb the laser beam. The optical path emitting unit includes a laser and a lens group. The laser beam of the laser emits a parallel laser beam after passing through the lens group.

3. A dust particle counter with adjustable particle size channel as claimed in claim 1, characterized in that: The n is equal to the number of channels of the dust particle counter.

4. A dust particle counter with adjustable particle size channel as claimed in claim 1, characterized in that: The signal amplifying circuit amplifies the voltage to between 0 and 12V.

5. The dust particle counter with adjustable particle size channel as claimed in claim 1, characterized in that: The voltage amplification factor of the primary voltage amplifier circuit is 5 times, the voltage amplification factor of the secondary voltage amplifier circuit is 10 times, and the voltage reduction factor of the voltage reduction circuit is 3 times.

6. A dust particle counter with adjustable particle size channel as claimed in claim 1, characterized in that: The chip model of the high-speed comparator is LM339DG or TLV3501, the digital-to-analog conversion circuit uses a DAC7502 or TLV5610 chip, and the high-speed comparator uses the voltage signal output by the chip used by the digital-to-analog conversion circuit as the reference voltage of the high-speed comparator for comparison.

7. A dust particle counter with adjustable particle size channel as claimed in claim 1, characterized in that: The chip model used by the four-to-one analog switch is CD4052 / TMUX6104.

8. The dust particle counter with adjustable particle size channel as claimed in claim 1, characterized in that: The dust particle counter also includes a liquid crystal display unit, a printer, a storage unit and a communication interface, and the liquid crystal display unit, the printer, the storage unit and the communication interface are respectively connected to the microprocessor.

9. A method for measuring a dust particle counter with an adjustable particle size channel, characterized in that: A dust particle counter according to any one of claims 1 to 7 is provided, wherein the method comprises the following steps: Step 1: adjusting each channel parameter of the dust particle counter according to the measurement requirements, wherein the parameters include the particle size value; Step 2, obtaining a voltage value corresponding to the particle size value according to the particle size spectrum, and connecting a four-choice analog switch to a primary voltage amplifier circuit, a secondary voltage amplifier circuit, a voltage reduction circuit or a voltage follower circuit according to the voltage value; Step 3, starting the signal acquisition device to absorb the sample gas into the particle counting sensor, and when the particle counting sensor receives the scattered light of the particles, it generates a pulse signal and outputs it to the signal processing device; Step 4: The pulse signal is filtered and amplified by a filtering circuit and a signal amplifying circuit; Step 5, processing the pulse signal according to the circuit connected by the four-to-one analog switch, and outputting the processed pulse signal to the high-speed comparator; Step 6: The high-speed comparator compares the voltage of the processed pulse signal with the reference voltage output by the digital-to-analog conversion chip. When the voltage of a pulse signal exceeds the reference voltage, a low level will be generated at the output of the high-speed comparator. Otherwise, the high-speed comparator maintains a high level. Step 7: The microprocessor receives the standard pulse signal output by the high-speed comparator, accumulates and counts the interrupts generated by the falling edge of the pulse through the pulse counting module, and finally converts it into a concentration value of the number of particles.

10. The method for measuring a dust particle counter with an adjustable particle size channel as claimed in claim 9, characterized in that: The concentration value in step 7 is the number of particles per unit volume.

Images