CN205826470U - A kind of PM2.5 sensor - Google Patents

Abstract

The utility model discloses a PM2.5 sensor, which automatically calibrates the detection results of the sensor through clean air, overcomes the error caused by the accumulation of particulate matter, and ensures high accuracy of the detection results of the sensor within the service period. The technical solution is: the PM2.5 sensor includes a detection gas channel, a calibration gas channel, a detection light source unit, a light receiving unit, a signal processing unit, a solenoid valve, a solenoid valve control unit and a detection chamber. The inlet channel of the detection room is divided into a detection gas channel and a calibration gas channel, and the outside air and filtered clean air are used respectively to obtain the detection concentration and background concentration of PM2.5, so that the detection concentration can be calibrated by using the background concentration.

Description

A PM2.5 sensor

technical field

The utility model relates to the field of PM2.5 particle concentration detection in the air, in particular to a sensor for PM2.5 detection based on a light scattering method.

Background technique

PM2.5 refers to particulate matter with an aerodynamic equivalent diameter less than or equal to 2.5 microns in the ambient air. It has a small particle size, a large area, and strong activity. It is easy to attach toxic and harmful substances (such as heavy metals, microorganisms, etc.), and stay in the atmosphere. The time is long and the transportation distance is long, so it has a great impact on human health and the quality of the atmospheric environment. In February 2012, the Ministry of Environmental Protection of China issued the "Ambient Air Quality Standard" (GB3095-2012), which added the concentration limit of PM2.5. Therefore, it is of great significance to accurately measure the concentration of PM2.5 in the air.

At present, sensors for detecting the mass concentration of suspended particulate matter in the air are mainly based on the principle of light scattering. According to the principle of light scattering, particles in the air will emit scattered light to the surrounding space under the irradiation of a certain intensity of light beam. The photodetector collects the scattered light pulse signal and converts it into a voltage pulse signal. The size of the pulse signal corresponds to the particle size of the particle, and the number of pulses corresponds to the number of particles. When the sampling gas flow rate and sampling time are fixed, the concentration of corresponding particles in a specific volume can be measured.

The PM2.5 sensor based on the principle of light scattering has a simple structure and low cost, and is convenient for real-time measurement. It is suitable for vehicle-mounted air purification systems to detect the concentration of PM2.5 inside and outside the vehicle. However, after a long period of use, particles will accumulate inside the sensor, and even adhere to the light source, optical path, and photodetector, causing errors in the collection of scattered light signals, resulting in inaccurate measurement results of the sensor.

Utility model content

A brief summary of one or more aspects is presented below to provide a basic understanding of these aspects. This summary is not an exhaustive overview of all contemplated aspects and is intended to neither identify key or critical elements of all aspects nor attempt to delineate the scope of any or all aspects. Its sole purpose is to present some concepts of one or more aspects in a simplified form as a prelude to the more detailed description that is presented later.

The purpose of this utility model is to solve the above problems. It provides a PM2.5 sensor, which automatically calibrates the detection results of the sensor through clean air, overcomes the error caused by the accumulation of particulate matter, and ensures that the detection results of the sensor within the service period have Higher accuracy.

The technical solution of the utility model is: the utility model discloses a PM2.5 sensor, including a detection gas channel, a calibration gas channel, a detection light source unit, a light receiving unit, a signal processing unit, a solenoid valve, a solenoid valve control unit and a detection chamber, wherein the solenoid valve control unit controls the solenoid valve to switch between the detection gas channel and the calibration gas channel, and the calibration gas channel filters the air to generate clean gas to pass into the detection chamber, The detection light source unit emits a light beam, the light receiving unit collects the generated scattered light and converts it into a voltage pulse signal, and the signal processing unit calculates the background concentration value of PM2.5 according to the received voltage pulse signal , the detection gas channel directly passes the external air into the detection chamber without filtering, and calculates the detection concentration value of PM2.5, and the signal processing unit uses the background concentration value of the PM2.5 to analyze the PM2.5 The detected concentration value is calibrated, and the calibrated PM2.5 concentration value is output.

According to an embodiment of the PM2.5 sensor of the present invention, the solenoid valve has a suction port connected to the gas inlet and two gas outlets respectively connected to the detection gas channel and the calibration gas channel.

According to an embodiment of the PM2.5 sensor of the present invention, the solenoid valve control unit includes a timing subunit and a solenoid valve switch subunit, wherein the timing subunit sets a certain time, and sends out Switching signal, the solenoid valve switch subunit controls the on-off of the solenoid valve according to the switching signal, and is used to switch the detection gas channel and the calibration gas channel.

According to an embodiment of the PM2.5 sensor of the present invention, the calibration gas channel is provided with a filter, and the filter captures fine particles in the air and filters the air to generate clean gas.

According to an embodiment of the PM2.5 sensor of the present invention, the detection light source unit includes a laser diode and a shaping lens, the laser diode emits a laser beam, and the shaping lens shapes the laser beam and projects it into the detection chamber.

According to an embodiment of the PM2.5 sensor of the present invention, the light receiving unit includes a photodiode and a converging lens, and the converging lens collects scattered light in the detection chamber and converges it to the photodiode, and the photodiode The optical signal is received and converted into a voltage pulse signal and sent to the signal processing unit.

According to an embodiment of the PM2.5 sensor of the present invention, the signal processing unit includes a signal amplification unit, a concentration calculation unit, a data storage unit, and a concentration calibration unit, and the voltage pulse signal is amplified by the signal amplification unit and then transmitted To the concentration calculation unit, the concentration calculation unit calculates and obtains the corresponding PM2.5 concentration signal according to the electrical signal, and the data storage unit is used to store the background concentration value of the PM2.5 and the detection of the PM2.5 concentration value, the concentration calibration unit calibrates the detected concentration value of PM2.5 according to the stored background concentration value of PM2.5.

According to an embodiment of the PM2.5 sensor of the present invention, the sensor also includes a sensor housing, the sensor housing is provided with an air inlet and a fan, the fan is turned on, and air enters from the air inlet The sensor is exhausted via the fan.

According to an embodiment of the PM2.5 sensor of the present utility model, the detection light source unit and the light receiving unit are both located in the detection chamber, and the two ends of the detection chamber are respectively connected to the air intake passage and the exhaust passage, so The exhaust channel is connected with the fan.

Compared with the prior art, the utility model has the following beneficial effects: the design of the PM2.5 sensor of the utility model is reasonable, the structure is simple, and the application is convenient. The PM2.5 sensor includes a detection gas channel, a calibration gas channel, a detection light source unit, a light receiving unit, a signal processing unit, a solenoid valve, a solenoid valve control unit and a detection chamber. The air inlet channel of the detection room is divided into a detection gas channel and a calibration gas channel, and the external air and filtered clean air are respectively used to obtain the detection concentration and background concentration of PM2.5, so that the background concentration can be used to calibrate the detection concentration, effectively The influence of particle accumulation on the output of the sensor is eliminated, the detection accuracy of PM2.5 concentration is improved, and the filtered clean air is used as a protective gas, which has a certain cleaning effect on the sensor and prolongs the service life of the sensor.

Description of drawings

Fig. 1 shows a schematic structural view of a preferred embodiment of the PM2.5 sensor of the present invention.

Fig. 2 shows a flow chart of a preferred embodiment of the PM2.5 concentration automatic calibration method based on the PM2.5 sensor.

Figure 3 shows a schematic diagram of a preferred embodiment of a solenoid valve control unit.

Figure 4 shows a schematic diagram of a preferred embodiment of the signal processing unit.

detailed description

After reading the detailed description of the embodiments of the present disclosure in conjunction with the following drawings, the above-mentioned features and advantages of the present utility model can be better understood. In the drawings, components are not necessarily drawn to scale, and components with similar related properties or characteristics may have the same or similar reference numerals.

Please refer to FIG. 1 , which shows the structure of a preferred embodiment of the PM2.5 sensor of the present invention. The PM2.5 sensor includes a detection gas channel 4, a calibration gas channel 5, a detection light source unit 7, a light receiving unit 9, a signal processing unit, a solenoid valve 3, an electronic valve control unit, and a detection chamber 8. The solenoid valve control unit controls the solenoid valve 3 to switch between the detection gas channel 4 and the calibration gas channel 5 . The calibration gas channel 5 filters the air to generate clean gas which passes into the detection chamber 8 . The detection light source unit 7 emits a light beam, and the light receiving unit 9 collects the generated scattered light and converts it into a voltage pulse signal. The signal processing unit calculates the background concentration value of PM2.5 according to the received voltage pulse signal. The detection gas channel 4 directly passes the external air into the detection chamber 8 without filtering, and calculates the detection concentration value of PM2.5. The signal processing unit uses the background concentration value of PM2.5 to calibrate the detected concentration value of PM2.5, and outputs the calibrated PM2.5 concentration value.

In addition, the sensor also includes a rectangular sensor housing 1, the air inlet 2 is located at the left end of the sensor housing 1, and the fan 11 is located on one side of the sensor housing 1, when the fan 11 is turned on, the air enters the sensor from the air inlet 2 and passes through Fan 11 discharges.

The sensor housing 1 is provided with a solenoid valve 3 , a detection gas channel 4 , a calibration gas channel 5 , a detection chamber 8 , and an exhaust channel 10 . The solenoid valve 3 has a suction port connected to the gas inlet 2 and two gas outlets respectively connected to the detection gas channel 4 and the calibration gas channel 5, and the solenoid valve 3 can communicate with the detection gas channel 5 at the gas inlet 2 Or switch between the connection between the gas inlet 2 and the calibration gas channel 5 . Specifically, as shown in Figure 3, the solenoid valve control unit includes a timing subunit 31 and a solenoid valve switch subunit 32. The timing subunit 31 sets a certain time, and after this certain time, a switching signal is sent, and the electromagnetic valve The valve switch subunit 32 controls the on-off of the solenoid valve 3 according to the switching signal, and is used for switching the detection gas channel 4 and the calibration gas channel 5 .

A filter 6 is provided in the calibration gas passage 5, which can capture fine particles in the air and filter the air to generate clean gas.

The detection chamber 8 is provided with a detection light source unit 7 and a light receiving unit 9 . One side of the detection chamber 8 is connected to the detection gas channel 4 , and the other side is connected to the exhaust channel 10 , and the exhaust channel 10 is connected to the fan 11 .

The detection light source unit 7 includes a laser diode and a shaping lens. The laser diode emits a laser beam, and the shaping lens shapes the laser beam and projects it into the detection chamber. A photodiode and a converging lens are included in the light receiving unit 9 . The converging lens collects the scattered light in the detection chamber 8 and converges it to the photodiode, and the photodiode receives the light signal and converts it into a voltage pulse signal and sends it to the signal processing unit.

As shown in FIG. 4 , the signal processing unit includes a signal amplification unit 121 , a concentration calculation unit 122 , a data storage unit 123 and a concentration calibration unit 124 . The voltage pulse signal is amplified by the signal amplification unit 121 and then transmitted to the concentration calculation unit 122. The concentration calculation unit 122 calculates and obtains the corresponding PM2.5 concentration signal according to the electrical signal. The data storage unit 123 is used to store the background concentration value of PM2.5 and PM2. .5, the concentration calibration unit 124 calibrates the detected concentration value of PM2.5 according to the stored background concentration value of PM2.5.

FIG. 2 further shows the working process of the PM2.5 sensor, that is, the process of using the PM2.5 sensor shown in FIG. 1 to automatically calibrate the PM2.5 concentration. Please refer to FIG. 2 , the detailed steps of the automatic calibration method in this embodiment are as follows.

Step S1: Control the solenoid valve, the air inlet is connected with the calibration gas channel, and the timing unit starts timing at the same time.

In this step, the solenoid valve is controlled by the electronic valve control unit so that the gas inlet is connected to the calibration gas channel. Then the air is filtered from the calibration gas channel and becomes clean air and enters the detection chamber.

Step S2: Turn on the laser diode, collect the scattered light intensity, and calculate the background concentration value of PM2.5.

In the detection chamber, the detection light source unit irradiates the clean air to form scattered light, and the light receiving unit receives the scattered light and converts it into an electrical signal. The signal processing unit calculates the background concentration value of PM2.5 according to the electrical signal generated by the light receiving unit, and stores the background concentration value.

Step S3: Determine whether the background concentration value of PM2.5 is less than the set threshold value, if it is less, go to step S4, otherwise go to step S5.

Step S4: Judging whether the timing has reached the set value, if so, go to step S6, otherwise go to step S1.

Whether the timing reaches the set time is judged by the timing subunit in the solenoid valve control unit.

Step S5: remind the user to clean the sensor, and then go to step S4.

When the background concentration of PM2.5 is lower than the set threshold, it means that the dust inside the sensor has accumulated too much, and the sensor needs to be cleaned.

Step S6: Control the solenoid valve, and connect the air inlet to the detection gas channel.

Indicates that the timing has reached the set time, then the timing sub-unit sends a switch switching signal of the solenoid valve, and the electronic valve switch sub-unit controls the solenoid valve according to the switch switching signal to connect the air inlet with the detection gas channel.

Step S7: collecting scattered light intensity, and calculating the detection concentration value of PM2.5.

The detection light source unit in the detection chamber irradiates the air to form scattered light, and the light receiving unit receives the scattered light and converts it into an electrical signal. The signal processing unit calculates the detected concentration value of PM2.5 according to the electrical signal generated by the light receiving unit, and stores the concentration value.

Step S8: Calibrate the detected concentration value of PM2.5 according to the background concentration value of PM2.5.

The calibration subunit in the signal processing unit calibrates the PM2.5 detection concentration value according to the PM2.5 background concentration value, so as to obtain the calibrated PM2.5 concentration value.

Step S9: Output the calibrated PM2.5 concentration value.

The previous description of the present disclosure is provided to enable any person skilled in the art to make or use the present disclosure. Various modifications to the present disclosure will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other variations without departing from the spirit or scope of the present disclosure. Thus, the disclosure is not intended to be limited to the examples and designs described herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims (9)

1. a PM2.5 sensor, it is characterised in that include detected gas passage, calibration gas passage, detection light source cell, Light receiving unit, signal processing unit, electromagnetic valve, control unit of electromagnetic valve and sensing chamber, wherein said control unit of electromagnetic valve Control described electromagnetic valve to switch between described detected gas passage and described calibration gas passage, described calibration gas passage pair Air filters, and is passed through described sensing chamber after producing clean gas, and described detection light source cell sends light beam, described light-receiving Unit is acquired and is converted into voltage pulse signal to the scattered light produced, and described signal processing unit is according to receiving Voltage pulse signal be calculated the background concn value of PM2.5, described detected gas passage directly by extraneous air without Filter is passed through sensing chamber, is calculated the detectable concentration value of PM2.5, and described signal processing unit utilizes the background of described PM2.5 dense The detectable concentration value of described PM2.5 is calibrated by angle value, and exports the PM2.5 concentration value after calibration.

PM2.5 sensor the most according to claim 1, it is characterised in that described electromagnetic valve have one with air inlet phase Air entry even and two gas outlets being connected with described detected gas passage and described calibration gas passage respectively.

PM2.5 sensor the most according to claim 2, it is characterised in that described control unit of electromagnetic valve includes timing Unit and electromagnetic valve switch subelement, wherein said timing subelement set one determine the time, through described determine the time after Sending switching signal, described electromagnetic valve switch subelement controls the break-make of described electromagnetic valve according to described switching signal, is used for cutting Change described detected gas passage and described calibration gas passage.

PM2.5 sensor the most according to claim 3, it is characterised in that described calibration gas passage is provided with filter, institute State the fine particle in filters trap air, filter to produce clean gas to air.

PM2.5 sensor the most according to claim 4, it is characterised in that described detection light source cell includes laser two pole Pipe and shaping lens, described laser diode sends laser beam, and described shaping lens will project after described laser beam shaping In sensing chamber.

PM2.5 sensor the most according to claim 5, it is characterised in that described light receiving unit includes photodiode And plus lens, described plus lens collects the scattered light in sensing chamber and converged to described photodiode, described light Electric diode receives optical signal and converts thereof into voltage pulse signal and send to described signal processing unit.

PM2.5 sensor the most according to claim 6, it is characterised in that described signal processing unit includes that signal amplifies Unit, concentration computing unit, data storage cell and concentration calibration unit, described voltage pulse signal amplifies through described signal After unit amplifies, transmission obtains corresponding to described concentration computing unit, described concentration computing unit according to signal of telecommunication calculating PM2.5 concentration signal, described data storage cell is in order to store background concn value and the detection of described PM2.5 of described PM2.5 Concentration value, the detectable concentration value of described PM2.5 is entered by described concentration calibration unit according to the background concn value of the PM2.5 stored Row calibration.

PM2.5 sensor the most according to claim 7, it is characterised in that described sensor also includes sensor housing, institute Stating and be provided with air inlet and fan on sensor housing, open described fan, air enters described sensor from described air inlet And discharge via described fan.

PM2.5 sensor the most according to claim 8, it is characterised in that described detection light source cell and described light-receiving Unit is respectively positioned in described sensing chamber, and the two ends of described sensing chamber connect inlet channel and exhaust passage respectively, and described aerofluxus is led to Road is connected with described fan.