High-precision particle detection sensor and detection method based on light scattering method

Abstract

The present invention relates to a high-precision particle detection sensor based on light scattering method and a detection method thereof, comprising a main control circuit board, a laser module, an air intake fan, a sensor base, a sensor upper cover, a shielding cover upper shell and a shielding cover lower shell, wherein the main control circuit board is assembled between the sensor base and the sensor upper cover; the main control circuit board is provided with an external interface, a power supply circuit module, a scattered light detection photodiode and an amplifier circuit, a laser tube drive circuit, a fan drive circuit and a temperature and humidity sensor circuit. The present invention more accurately calculates the mass concentration of suspended particles in the air by introducing a method of average amplitude participation in the calculation, eliminates the defect of the method of converting the mass concentration of particles by only counting the number of particles, and is suitable for the mass concentration collection of various different particle material environments; by defining the method of defining different particle size baselines, the boundaries of individual particle size groups are strictly distinguished and accurately calculated, so that the mass concentration of each particle size group is more accurate.

Description

Technical Field

[0001] The present invention belongs to the technical field of suspended particle mass concentration detection, and in particular relates to a high-precision particle detection sensor based on a light scattering method and a detection method thereof. Background Art

[0002] With the application of grid monitoring methods in air quality detection systems, sensors that use laser scattering to measure particle mass concentration are gradually being used on a large scale in urban environmental quality monitoring and governance projects because of their small size and low cost. However, compared with large and high-cost sensing equipment, particle concentration detection sensors based on laser scattering have the disadvantages of low detection accuracy and small detection range, especially in the particle size range of about 10μm, which is much lower than standard large equipment. This defect often leads to significant differences in PM10 monitoring indicators between grid monitoring equipment and standard station equipment. At the same time, the particle sensors on the market have inaccurate measurement data due to long-term internal dust accumulation, which greatly increases the probability of sensor repair and maintenance costs.

[0003] This patent has made effective technical corrections to the laser scattering method for measuring particulate mass concentration, and overcomes the measurement error caused by long-term internal dust accumulation in hardware structure. At the same time, temperature and humidity correction parameters are introduced to improve the acquisition accuracy of the laser scattering particulate mass concentration sensor using a more scientific method and solve the existing application problems of particulate matter sensors. Summary of the invention

[0004] In view of this, the purpose of the present invention is to provide a high-precision particle detection sensor based on the light scattering method, aiming to solve the defects of the method of converting the mass concentration of particles by counting the number of particles, and adopt multiple detection methods to make the mass concentration and measurement error more accurate.

[0005] In order to achieve the above purpose, the technical solutions adopted are as follows:

[0006] A high-precision particle detection sensor based on light scattering method includes a main control circuit board, a laser module, an intake fan, a sensor base, a sensor upper cover, a shielding cover upper shell and a shielding cover lower shell. The main control circuit board is assembled between the sensor base and the sensor upper cover;

[0007] The main control circuit board is provided with an external interface, a power supply circuit module, a scattered light detection photodiode and an amplifier circuit, a laser tube drive circuit, a fan drive circuit and a temperature and humidity sensor circuit, and the fan drive circuit is electrically connected to the intake fan;

[0008] The laser module includes a laser diode, a nickel-plated copper tube, a compression spring, a condenser, a laser fixing seat and a laser sensor circuit board. The condenser, the compression spring and the laser diode are placed in the nickel-plated copper tube in sequence. The rear end pin of the laser diode is welded with a laser sensor circuit board. The assembled nickel-plated copper tube is inserted into the mounting hole on the laser fixing seat. The laser fixing seat is set on the main control circuit board. At the same time, the laser sensor circuit board is welded to the corresponding pads of the main control circuit board to complete the electrical connection.

[0009] As a further improvement of the present invention, an air intake channel, a light trap, a collection area, a laser fixed tube slot and a fan fixed lower slot are arranged in the sensor base, and the inner surfaces of the air intake channel, the light trap, the collection area and the fan fixed lower slot are all mirror-finished to prevent the accumulation of particles, the collection area is connected with the air intake channel, and the collection area is connected with the fan fixed lower slot, and the cross-sectional area of ​​the collection area is smaller than the cross-sectional area of ​​other parts of the channel, so as to restrict the number of particles passing through the collection area per unit time, and in addition, the laser fixed tube slot, the collection area and the light trap are connected in sequence;

[0010] A fan fixing upper groove and an air inlet nozzle are provided inside the sensor upper cover. After the sensor upper cover and the sensor base are correspondingly snapped together and assembled, the main control circuit board is fixed between the sensor upper cover and the sensor base, and the fan fixing upper groove and the fan fixing lower groove are jointly clamped to the air intake fan. At the same time, the laser fixing seat is clamped in the laser fixing tube clamping groove, and the air inlet channels of the air inlet nozzle are correspondingly connected, and the air inlet channel, the light trap, and the collection area form a closed space.

[0011] As a further improvement of the present invention, the external interface is connected to a DC power supply to perform digital communication with the processor, and the power supply circuit module filters and performs low-voltage difference linear voltage stabilization on the connected DC power supply to power the scattered light detection photodiode and amplifier circuit, the laser tube drive circuit, the fan drive circuit and the temperature and humidity sensor circuit;

[0012] The scattered light detection photodiode and the amplifier circuit perform photoelectric conversion and signal amplification on the scattered light, and transmit the signal to the processor through the external interface for calculation;

[0013] The laser tube driving circuit is connected to the processor via an external interface, thereby controlling the opening and closing of the laser diode;

[0014] The fan driving circuit is connected to the processor via an external interface to control the rotation state of the intake fan;

[0015] The temperature and humidity sensor is connected to the processor via an external interface to collect temperature and humidity information.

[0016] As a further improvement of the present invention, two grounding through holes are provided on the sensor base, and one grounding through hole is provided on the sensor cover. The grounding through hole is used to place a grounding spring that connects the digital ground on the main control circuit board with the upper shell and the lower shell of the shielding cover.

[0017] As a further improvement of the present invention, the sensor base and the sensor cover are fastened by a plurality of self-tapping screws.

[0018] As a further improvement of the present invention, buckles for fixing the upper shell of the shielding cover and the lower shell of the shielding cover are arranged on the surrounding surfaces of the sensor base.

[0019] As a further improvement of the present invention, the laser diode and the nickel-plated copper tube are fastened by interference fit.

[0020] As a further improvement of the present invention, ventilation holes are provided at positions of the upper shell and the lower shell of the shielding cover corresponding to the air intake fan.

[0021] The detection method of the high-precision particle detection sensor based on the light scattering method includes the following steps:

[0022] PA0: sensor powered on;

[0023] PA1: Turn off the laser diode, detect the basic voltage line of the amplifier circuit, and calibrate to zero;

[0024] PA2: Determine the calibration flag; if it is 0, enter the calibration program PB1, if it is 1, enter the detection program PC1;

[0025] PB1: calibration procedure;

[0026] PC1: Turn on the laser diode and the program measures the average amplitude of the amplified scattered light pulse;

[0027] PC2: The program measures the pulse width of each scattered light pulse;

[0028] PC3: The program records the number of pulses per unit time t;

[0029] PC4: Filtering based on pulse width;

[0030] PC5: Integrate the product of the number of pulses and the average amplitude;

[0031] PC6: bring in the calibration coefficient;

[0032] PC7: Collect temperature and humidity values ​​and input temperature and humidity coefficients;

[0033] PC8: time window sliding average;

[0034] PC9: Actively report results through external interfaces;

[0035] The calibration method of the sensor to detect particle concentration includes the following steps: Standard particle test chamber calibration

[0036] PB101: In the standard chamber, turn on the laser diode and use the standard PM2.5 particle generator to generate a particle environment with a standard concentration. After the PM2.5 concentration is detected by standard equipment and stabilized, collect the average amplitude of the scattered light pulse to determine the PM2.5 baseline.

[0037] PB102: In the standard chamber, use a standard PM2.5 particle generator to generate a particle environment higher than the sensor range. After the PM2.5 concentration is detected by standard equipment and stabilized, start recording the product of the average amplitude of the scattered light pulse and the number of pulses, and record the PM2.5 detection results of the standard equipment at the same time;

[0038] PB103 is in the standard chamber, the purification device is turned on, and two results within the full range are recorded;

[0039] PB104: Get PM2.5 compensation result and generate calibration coefficient;

[0040] PB105: In the standard chamber, turn on the laser diode and use the standard PM10 particle generator to generate a particle environment with a standard concentration. After the PM10 concentration is detected by standard equipment and stabilized, collect the average amplitude of the scattered light pulse to determine the PM10 baseline.

[0041] PB106: In the standard chamber, a standard PM10 particle generator is used to generate a particle environment higher than the sensor range. After the PM10 concentration is detected by standard equipment and stabilized, the product of the average amplitude of the scattered light pulse and the number of pulses is recorded, and the PM10 detection results of the standard equipment are recorded at the same time;

[0042] PB107: In the standard chamber, turn on the purification device and record two results within the full range;

[0043] PB108: Get PM10 compensation result and generate calibration coefficient;

[0044] PB109: Set the calibration flag to 1.

[0045] The beneficial effects of the present invention are:

[0046] 1. The mass concentration of suspended particles in the air can be more accurately calculated by introducing the method of average amplitude participation in the calculation, eliminating the defect of the method of converting the mass concentration of particles by only counting the number of particles, and is suitable for the mass concentration collection of various different particle material environments;

[0047] 2. By defining the baselines of different particle sizes, the boundaries of individual particle size groups are strictly distinguished and accurately calculated, making the mass concentration of each particle size group more accurate;

[0048] 3. By introducing temperature and humidity correction parameters, the measurement errors caused by temperature and humidity changes can be offset;

[0049] 4. Through hardware structure design, the measurement error caused by dust accumulation inside the sensor can be effectively solved, and the measurement error introduced by various interferences can be effectively solved by using pulse width filtering method. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] The drawings constituting a part of this application are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0051] Figure 1 It is a structural schematic diagram of the sensor involved in the present invention;

[0052] Figure 2 It is a structural schematic diagram of the main control circuit board involved in the present invention;

[0053] Figure 3 It is a structural schematic diagram of the laser module involved in the present invention;

[0054] Figure 4 It is a structural schematic diagram of the sensor base involved in the present invention;

[0055] Figure 5 It is a structural schematic diagram of the sensor cover involved in the present invention;

[0056] Figure 6 It is a schematic diagram of the detection process of the high-precision particle detection sensor based on the light scattering method in the present invention. DETAILED DESCRIPTION

[0057] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present invention will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0058] In order to enable those skilled in the art to better understand the solution of the present application, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present application.

[0059] Please refer to Figure 1-6The high-precision particle detection sensor based on the light scattering method includes a main control circuit board 100, a laser module 200, an intake fan 300, a sensor base 400, a sensor upper cover 500, a shielding cover upper shell 600 and a shielding cover lower shell 700. The main control circuit board 100 is assembled between the sensor base 400 and the sensor upper cover 500. The sensor base 400 and the sensor upper cover 500 are fastened by a plurality of self-tapping screws. Buckles 407 for fixing the shielding cover upper shell 600 and the shielding cover lower shell 700 are arranged on the outer surface of the sensor base 400. Ventilation holes 607 are opened on the shielding cover upper shell 600 and the shielding cover lower shell 700 at the position corresponding to the intake fan 300.

[0060] The main control circuit board 100 is provided with an external interface 101, a power supply circuit module 102, a scattered light detection photodiode and an amplifier circuit 103, a laser tube drive circuit 104, a fan drive circuit 105 and a temperature and humidity sensor circuit 106. The fan drive circuit 105 is electrically connected to the intake fan 300. In addition, the external interface 101 on the main control circuit board 100 is the only interface connected to the outside world. The external interface 101 is connected to a DC power supply to communicate digitally with the processor. The power supply circuit module 102 filters and performs low-voltage difference linear voltage regulation on the connected DC power supply to provide the scattered light detection photodiode and amplifier circuit 103, the laser tube drive circuit 104, and the fan drive circuit 105. The circuit 104, the fan driving circuit 105 and the temperature and humidity sensor circuit 106 are powered; the scattered light detection photodiode and the amplifier circuit 103 are responsible for photoelectric conversion and signal amplification of the scattered light in the scattered light path, and transmit it to the processor for calculation through the external interface 101; the laser tube driving circuit 104 is connected to the processor through the external interface 101, so as to control the opening and closing of the laser diode 201; the fan driving circuit 105 is connected to the processor through the external interface 101 to control the rotation state of the intake fan 300; the temperature and humidity sensor 106 is connected to the processor through the external interface 101 to collect temperature and humidity information;

[0061] The laser module 200 includes a laser diode 201, a nickel-plated copper tube 202, a compression spring 203, a condenser 204, a laser fixing seat 205 and a laser sensor circuit board 206. The condenser 204, the compression spring 203 and the laser diode 201 are placed in the nickel-plated copper tube 202 in sequence. The laser diode 201 and the nickel-plated copper tube 202 are fastened by interference fit. The rear end pin of the laser diode 201 is welded with a laser sensor circuit board 206. After assembly, the nickel-plated copper tube 202 is inserted into the mounting hole a on the laser fixing seat 205. The laser fixing seat 205 is set on the main control circuit board 100. At the same time, the laser sensor circuit board 206 is welded to the corresponding pads of the main control circuit board 100 to complete the electrical connection.

[0062] The sensor base 400 is provided with an air intake channel 401, a light trap 402, a collection area 403, a laser fixed tube clamping slot 404 and a fan fixed lower slot 405. The inner surfaces of the air intake channel 401, the light trap 402, the collection area 403 and the fan fixed lower slot 405 are all mirror-finished to prevent the accumulation of particles. The collection area 403 is communicated with the air intake channel 401, and the collection area 403 is communicated with the fan fixed lower slot 405. The cross-sectional area of ​​the collection area 403 is smaller than the cross-sectional area of ​​other parts of the channel, so as to restrict the number of particles passing through the collection area 403 per unit time.

[0063] The sensor upper cover 500 is provided with a fan fixing upper groove 501 and an air inlet nozzle 502. After the sensor upper cover 500 and the sensor base 400 are correspondingly snapped together and assembled, the main control circuit board 100 is fixed between the sensor upper cover 500 and the sensor base 400, and the fan fixing upper groove 501 and the fan fixing lower groove 405 are jointly clamped to the intake fan 300. At the same time, the laser fixing seat 205 is clamped in the laser fixing tube clamping groove 404, and the air inlet nozzle 502 is correspondingly connected to the air inlet channel 401, and the air inlet channel 401, the light trap 402, and the collection area 403 form a closed space.

[0064] The sensor base 400 is provided with two grounding through holes 406, and the sensor upper cover 500 is provided with a grounding through hole 406, and the grounding through hole 406 is used to place a grounding spring that connects the digital ground on the main control circuit board 100 with the shielding cover upper shell 600 and the shielding cover lower shell 700.

[0065] The method for detecting the concentration of particulate matter by using a sensor comprises the following steps:

[0066] PA0: sensor powered on;

[0067] PA1: Turn off the laser diode 201, detect the basic voltage line of the amplifier circuit, and calibrate to zero;

[0068] PA2: Determine the calibration flag; if it is 0, enter the calibration program PB1, if it is 1, enter the detection program PC1;

[0069] PB1: calibration procedure;

[0070] PC1: Turn on the laser diode 201, and the program measures the average amplitude of the amplified scattered light pulse;

[0071] PC2: The program measures the pulse width of each scattered light pulse;

[0072] PC3: The program records the number of pulses per unit time t;

[0073] PC4: Filtering based on pulse width;

[0074] PC5: Integrate the product of the number of pulses and the average amplitude;

[0075] PC6: bring in the calibration coefficient;

[0076] PC7: Collect temperature and humidity values ​​and input temperature and humidity coefficients;

[0077] PC8: time window sliding average;

[0078] PC9: Actively report results through external interfaces;

[0079] The calibration method for detecting particle concentration by the sensor comprises the following steps:

[0080] Calibration of standard particle chamber

[0081] PB101: In the standard chamber, turn on the laser diode 201, use the standard PM2.5 particle generator to generate a particle environment with a standard concentration, use standard equipment to detect the PM2.5 concentration until it is stable, collect the average amplitude of the scattered light pulse, and determine the PM2.5 baseline;

[0082] PB102: In the standard chamber, use a standard PM2.5 particle generator to generate a particle environment higher than the sensor range. After the PM2.5 concentration is detected by standard equipment and stabilized, start recording the product of the average amplitude of the scattered light pulse and the number of pulses, and record the PM2.5 detection results of the standard equipment at the same time;

[0083] PB103 is in the standard chamber, the purification device is turned on, and two results within the full range are recorded;

[0084] PB104: Get PM2.5 compensation result and generate calibration coefficient;

[0085] PB105: In the standard chamber, turn on the laser diode 201, use the standard PM10 particle generator to generate a particle environment of standard concentration, use standard equipment to detect the PM10 concentration and after it stabilizes, collect the average amplitude of the scattered light pulse to determine the PM10 baseline;

[0086] PB106: In the standard chamber, a standard PM10 particle generator is used to generate a particle environment higher than the sensor range. After the PM10 concentration is detected by standard equipment and stabilized, the product of the average amplitude of the scattered light pulse and the number of pulses is recorded, and the PM10 detection results of the standard equipment are recorded at the same time;

[0087] PB107: In the standard chamber, turn on the purification device and record two results within the full range;

[0088] PB108: Get PM10 compensation result and generate calibration coefficient;

[0089] PB109: Set the calibration flag to 1.

[0090] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A detection method of a high-precision particle detection sensor based on a light scattering method, characterized in that: It includes a main control circuit board, a laser module, an air intake fan, a sensor base, a sensor upper cover, a shielding cover upper shell and a shielding cover lower shell, and the main control circuit board is assembled between the sensor base and the sensor upper cover; The main control circuit board is provided with an external interface, a power supply circuit module, a scattered light detection photodiode and an amplifier circuit, a laser tube drive circuit, a fan drive circuit and a temperature and humidity sensor circuit, and the fan drive circuit is electrically connected to the intake fan; The laser module includes a laser diode, a nickel-plated copper tube, a compression spring, a condenser, a laser fixing seat and a laser sensor circuit board. The condenser, the compression spring and the laser diode are placed in the nickel-plated copper tube in sequence. The laser sensor circuit board is welded to the rear pin of the laser diode. The assembled nickel-plated copper tube is plugged into the mounting hole on the laser fixing seat. The laser fixing seat is set on the main control circuit board. At the same time, the laser sensor circuit board is welded to the corresponding pads of the main control circuit board to complete the electrical connection. An air intake channel, a light trap, a collection area, a laser fixed tube slot and a fan fixed lower slot are arranged in the sensor base. The inner surfaces of the air intake channel, the light trap, the collection area and the fan fixed lower slot are all mirror-finished to prevent the accumulation of particles. The collection area is connected with the air intake channel, and the collection area is connected with the fan fixed lower slot. The cross-sectional area of ​​the collection area is smaller than the cross-sectional area of ​​other parts of the channel, which is used to restrict the number of particles passing through the collection area per unit time. In addition, the laser fixed tube slot, the collection area and the light trap are connected in sequence; A fan fixing upper groove and an air inlet nozzle are arranged inside the sensor upper cover. After the sensor upper cover and the sensor base are correspondingly buckled and assembled, the main control circuit board is fixed between the sensor upper cover and the sensor base, and the fan fixing upper groove and the fan fixing lower groove are connected to the air inlet fan together. At the same time, the laser fixing seat is connected to the laser fixing pipe slot, and the air inlet nozzle air inlet channel is correspondingly connected, so that the air inlet channel, the light trap and the collection area form a closed space; The external interface is connected to a DC power supply to communicate digitally with the processor. The power supply circuit module filters and performs low-voltage difference linear voltage regulation on the connected DC power supply to supply power to the scattered light detection photodiode and amplifier circuit, laser tube drive circuit, fan drive circuit and temperature and humidity sensor circuit. The scattered light detection photodiode and amplifier circuit convert the scattered light into photoelectricity and amplify the signal, and transmit it to the processor through the external interface for calculation; The laser tube driving circuit is connected to the processor through an external interface to control the opening and closing of the laser diode; The fan drive circuit is connected to the processor via an external interface to control the rotation state of the intake fan; The temperature and humidity sensor is connected to the processor through an external interface to collect temperature and humidity information; Two grounding through holes are arranged on the sensor base, and one grounding through hole is arranged on the sensor upper cover, and the grounding through hole is used to place a grounding spring that connects the digital ground on the main control circuit board with the upper shell and the lower shell of the shielding cover; The sensor base and sensor cover are fastened by several self-tapping screws; Buckles for fixing the upper shell of the shielding cover and the lower shell of the shielding cover are arranged on the surfaces around the sensor base; The laser diode and the nickel-plated copper tube are fastened by interference fit; Ventilation holes are provided on the upper shell of the shielding cover and the lower shell of the shielding cover at positions corresponding to the air intake fans; The detection method includes the following steps: PA0: sensor powered on; PA1: Turn off the laser diode, detect the basic voltage line of the amplifier circuit, and calibrate to zero; PA2: Determine the calibration flag; if it is 0, enter the calibration program PB1, if it is 1, enter the detection program PC1; PB1: calibration procedure; PC1: Turn on the laser diode and the program measures the average amplitude of the amplified scattered light pulse; PC2: The program measures the pulse width of each scattered light pulse; PC3: The program records the number of pulses per unit time t; PC4: Filtering based on pulse width; PC5: Integrate the product of the number of pulses and the average amplitude; PC6: bring in the calibration coefficient; PC7: Collect temperature and humidity values ​​and input temperature and humidity coefficients; PC8: time window sliding average; PC9: Actively report results through external interfaces; The calibration method of the sensor to detect particle concentration is as follows: Calibration of standard particle test chamber; PB101: In the standard chamber, turn on the laser diode and use the standard PM2.5 particle generator to generate a standard concentration of particulate matter. After the PM2.5 concentration is stable, use standard equipment to detect it, collect the average amplitude of the scattered light pulse, and determine the PM2.5 baseline. PB102: In the standard chamber, use a standard PM2.5 particle generator to generate a particle environment higher than the sensor range. After the PM2.5 concentration is detected by standard equipment and stabilized, start recording the product of the average amplitude of the scattered light pulse and the number of pulses, and record the PM2.5 detection results of the standard equipment at the same time; PB103: In the standard chamber, turn on the purification device and record two results within the full range; PB104: Get PM2.5 compensation result and generate calibration coefficient; PB105: In the standard chamber, turn on the laser diode and use the standard PM10 particle generator to generate a particle environment with a standard concentration. After the PM10 concentration is detected by standard equipment and stabilized, collect the average amplitude of the scattered light pulse to determine the PM10 baseline. PB106: In the standard chamber, a standard PM10 particle generator is used to generate a particle environment higher than the sensor range. After the PM10 concentration is detected by standard equipment and stabilized, the product of the average amplitude of the scattered light pulse and the number of pulses is recorded, and the PM10 detection results of the standard equipment are recorded at the same time; PB107: In the standard chamber, turn on the purification device and record two results within the full range; PB108: Get PM10 compensation result and generate calibration coefficient; PB109: Set the calibration flag to 1.

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