CN116539535A - Photoacoustic cell, system and method for aerosol acidity detection - Google Patents
Photoacoustic cell, system and method for aerosol acidity detection Download PDFInfo
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- G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
- G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
- G01N21/1702—Systems in which incident light is modified in accordance with the properties of the material investigated with opto-acoustic detection, e.g. for gases or analysing solids
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
- G01N21/01—Arrangements or apparatus for facilitating the optical investigation
- G01N21/03—Cuvette constructions
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- G—PHYSICS
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- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
- G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
- G01N21/1702—Systems in which incident light is modified in accordance with the properties of the material investigated with opto-acoustic detection, e.g. for gases or analysing solids
- G01N2021/1708—Systems in which incident light is modified in accordance with the properties of the material investigated with opto-acoustic detection, e.g. for gases or analysing solids with piezotransducers
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- Investigating Or Analysing Materials By Optical Means (AREA)
Abstract
The invention discloses a photoacoustic cell, a system and a method for aerosol acidity detection, comprising a shell, an optical window, an air inlet pipeline, an air outlet pipeline, a photoacoustic resonant cavity penetrating through the shell and a piezoelectric ceramic sensor in the shell, wherein the optical window is respectively arranged at two ends of the boundary between the photoacoustic resonant cavity and the shell, the air inlet pipeline and the air outlet pipeline are respectively connected with two ends of the photoacoustic resonant cavity through the shell, and the piezoelectric ceramic sensor is arranged in the cross section direction of the photoacoustic resonant cavity; aerosol enters the photoacoustic resonant cavity from the air inlet pipeline and is guided out from the air outlet pipeline; the piezoelectric ceramic sensor is used for detecting the photoacoustic signal of the aerosol in the photoacoustic resonant cavity. The embodiment of the invention can be widely applied to the technical field of detection, and can be used for detecting the acidity of the aerosol.
Description
Technical Field
The invention relates to the technical field of detection, in particular to a photoacoustic cell, a photoacoustic cell system and a photoacoustic cell method for aerosol acidity detection.
Background
The pH of a solution is one of its most basic chemical properties, affecting the chemical reaction pathways and kinetics in various fields, and the atmosphere is no exception. The pH of the atmospheric coacervate drives a critical chemical reaction that ultimately affects the global climate in a number of ways. The condensed phase consists mainly of suspended liquid or solid particles, called atmospheric aerosols, unlike cloud droplets due to their much smaller size (mainly <10 μm). The pH (acidity) of the atmospheric aerosol can enhance certain chemical reactions, leading to the formation of additional condensed phase mass of low volatile species, changing the optical and water absorption properties of the particles, and dissolving metal ions, creating a threat to human health after inhalation. However, while the acidity of aerosols is important for climate and human health, the basic knowledge of their acidity has been limited due to the size of aerosols (more than 99% by number of particles are less than 1 μm) and the complexity of their internal composition.
In one atmosphere particle, there may be hundreds to thousands of different chemical species, different water content, high ionic strength and different phases (liquid, semi-solid and solid), making aerosol analysis more challenging, atmosphere particles evolve through heterogeneous chemical reactions with gases and heterogeneous chemical reactions within the condensed phase.
The traditional measurement method of aerosol acidity comprises the following steps: 1. the particle sample is collected and extracted by a filter, analyzed under vacuum, or dried during or after collection and then dissolved in water to analyze its composition, which has a disadvantage in that the inside of aerosol H is in the course of the treatment + The activity is not conservation, and the change of the water content in the particles influences the activity, so that the accuracy of the acidity of the aerosol is influenced; 2. the volume concentration of aerosol particles in combination with the gas concentration is used to predict the water content, and thus the acidity is deduced from some thermodynamic equilibrium conditions. However, the model cannot be accurately calculated in consideration of complex chemical environment inside the particles.
Disclosure of Invention
In view of the above, it is an object of embodiments of the present invention to provide a photoacoustic cell, a system and a method for aerosol acidity detection, which can improve the accuracy of aerosol acidity detection.
In a first aspect, an embodiment of the present invention provides a photoacoustic cell for aerosol acidity detection, including a housing, an optical window, an air inlet pipe, an air outlet pipe, a photoacoustic resonant cavity penetrating the housing, and a piezoelectric ceramic sensor in the housing, wherein the optical window is respectively installed at two ends of a boundary between the photoacoustic resonant cavity and the housing, the air inlet pipe and the air outlet pipe are respectively connected with two ends of the photoacoustic resonant cavity through the housing, and the piezoelectric ceramic sensor is installed in a cross section direction of the photoacoustic resonant cavity; aerosol enters the photoacoustic resonant cavity from the air inlet pipeline and is guided out from the air outlet pipeline; the piezoelectric ceramic sensor is used for detecting the photoacoustic signal of the aerosol in the photoacoustic resonant cavity.
Optionally, a cylindrical groove is formed in the shell, a fixing groove is formed in the cylindrical groove, and the piezoelectric ceramic sensor is installed in the cylindrical groove and is positioned by the fixing groove.
Optionally, deionized water or turpentine is filled in the gap between the cylindrical recess and the piezoceramic sensor to exclude air.
Optionally, the photoacoustic cell further comprises a flange by which the piezoceramic sensor is secured to the housing and by which the optical window is secured to the housing.
Optionally, the material of the optical window comprises an infrared crystalline material comprising any one of magnesium fluoride, zinc sulfide, zinc selenide, sapphire, or silicon.
Optionally, the material of the housing comprises any one of stainless steel, quartz or an aluminum alloy.
Optionally, the piezoceramic sensor comprises any one of a hydrophone, a tuning fork, or a miniature microphone.
Optionally, the photoacoustic resonant cavity comprises a cylindrical or square shape.
In a second aspect, an embodiment of the present invention provides a system for detecting acidity of an aerosol, including a laser light source, a chopper, an amplifier, an oscilloscope, and the photoacoustic cell described above; wherein, the liquid crystal display device comprises a liquid crystal display device,
a laser light source for generating laser light and emitting the laser light to the chopper;
the chopper is used for modulating the incoming laser and transmitting the modulated laser into the photoacoustic resonant cavity of the photoacoustic cell;
the photoacoustic cell is used for collecting electric signals corresponding to acoustic-optical signals generated by aerosol in the photoacoustic resonant cavity;
an amplifier for amplifying the electrical signal;
and the oscilloscope is used for collecting the amplified electric signals.
In a third aspect, an embodiment of the present invention provides a method for detecting acidity of an aerosol, which is applied to the above system, and includes:
preparing aerosol from the acidic solution through an aerosol generator, and filling the aerosol into a photoacoustic resonance cavity of the photoacoustic cell;
determining control parameters of a laser light source and a chopper, and starting the laser light source and the chopper;
collecting an electric signal through an oscilloscope, and determining the acidity of the aerosol according to a standard curve and the collected electric signal; the standard curve characterizes a relationship of known acidity and electrical signal.
The embodiment of the invention has the following beneficial effects: the photoacoustic cell for detecting the acidity of the aerosol in the embodiment comprises a shell, an optical window, an air inlet pipeline, an air outlet pipeline, a photoacoustic resonant cavity penetrating through the shell and a piezoelectric ceramic sensor in the shell, wherein the aerosol enters the photoacoustic resonant cavity from the air inlet pipeline and is guided out from the air outlet pipeline, and the piezoelectric ceramic sensor is used for detecting a photoacoustic signal of the aerosol in the photoacoustic resonant cavity; the system for detecting the acidity of the aerosol comprises a laser light source, a chopper, an aerosol generator, an amplifier, an oscilloscope and a photoacoustic cell, wherein laser generated by the laser light source is modulated by the chopper and then is emitted into a photoacoustic resonant cavity in the photoacoustic cell, a photoacoustic signal of the aerosol is measured by a piezoelectric ceramic sensor, the photoacoustic signal of the aerosol is collected by the amplifier and the oscilloscope, and finally the acidity of the aerosol is determined according to the photoacoustic signal of the aerosol, so that the acidity of the aerosol is measured by a laser spectrum, and the accuracy of detecting the acidity of the aerosol is improved.
Drawings
FIG. 1 is a side view of a photoacoustic cell for aerosol acidity detection according to an embodiment of the present invention;
fig. 2 is a perspective view of a photoacoustic cell for aerosol acidity detection according to an embodiment of the present invention;
FIG. 3 is a block diagram of a system for aerosol acidity detection provided by an embodiment of the present invention;
fig. 4 is a schematic flow chart of steps of a method for detecting acidity of aerosol according to an embodiment of the present invention.
Detailed Description
The invention will now be described in further detail with reference to the drawings and to specific examples. The step numbers in the following embodiments are set for convenience of illustration only, and the order between the steps is not limited in any way, and the execution order of the steps in the embodiments may be adaptively adjusted according to the understanding of those skilled in the art.
In the following description, reference is made to "some embodiments" which describe a subset of all possible embodiments, but it is to be understood that "some embodiments" can be the same subset or different subsets of all possible embodiments and can be combined with one another without conflict.
In the following description, the terms "first", "second", "third" and the like are merely used to distinguish similar objects and do not represent a particular ordering of the objects, it being understood that the "first", "second", "third" may be interchanged with a particular order or sequence, as permitted, to enable embodiments of the invention described herein to be practiced otherwise than as illustrated or described herein.
Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The terminology used in the embodiments of the invention is for the purpose of describing embodiments of the invention only and is not intended to be limiting of the invention.
Before describing embodiments of the present invention in further detail, the terms and terminology involved in the embodiments of the present invention will be described, and the terms and terminology involved in the embodiments of the present invention will be used in the following explanation.
The photoacoustic spectroscopy technology can realize detection of trace gas, can monitor and analyze solid and liquid, and a lot of scientific researches are focused on researching environmental problems such as greenhouse effect, acid rain, ozone layer damage and the like, and can be used for measuring pollution caused by biological fermentation and automobile exhaust emission and related problems such as nitrogen detection of soil nitride, plant physiology and biological systems, non-destructive breath analysis in microbiology and medicine, oil gas leakage and the like.
Photoacoustic spectrometry is a laser spectrum detection technique based on the photoacoustic effect. The principle is as follows: after the substance to be measured absorbs laser energy, the substance molecules transit from a ground state to an excited state, but due to the instability of the excited state of a high energy level, the substance molecules return to the ground state again through collision relaxation, and meanwhile, the absorbed light energy is converted into the translational energy of the molecules according to the energy conservation law, so that a pressure wave is formed in the photoacoustic cell. When the laser is modulated at a certain frequency, the local temperature is periodically increased and decreased, so that an acoustic wave signal consistent with the laser modulation frequency is generated. The intensity of the pressure wave is detected by using a piezoelectric ceramic sensor, and the quantity of molecules excited by the absorbed light in the photoacoustic cell is determined according to the proportional relation between the amplitude of the photoacoustic signal and the intensity, concentration and content of the incident light. The photoacoustic spectrum sensing process can be described as a process in which a substance absorbs light energy to generate periodic thermal expansion, thereby causing weak sound pressure waves (ultrasonic waves), and a sensor is used to detect fluctuation of the sound pressure waves to determine the concentration of gas.
The embodiment of the invention provides a photoacoustic cell for aerosol acidity detection, which comprises a shell, an optical window, an air inlet pipeline, an air outlet pipeline, a photoacoustic resonant cavity penetrating the shell and a piezoelectric ceramic sensor in the shell, wherein the optical window is respectively arranged at two ends of the boundary between the photoacoustic resonant cavity and the shell, the air inlet pipeline and the air outlet pipeline are respectively connected with two ends of the photoacoustic resonant cavity through the shell, and the piezoelectric ceramic sensor is arranged in the cross section direction of the photoacoustic resonant cavity; aerosol enters the photoacoustic resonant cavity from the air inlet pipeline and is guided out from the air outlet pipeline; the piezoelectric ceramic sensor is used for detecting the photoacoustic signal of the aerosol in the photoacoustic resonant cavity.
Since the absorption of laser energy by aerosol with different acidity is also different, the stronger the acidity is, the stronger the absorption is, and the generated photoacoustic signal is also stronger, so that the aerosol acidity can be detected by measuring the photoacoustic signal. Meanwhile, the photoacoustic cell and the photoacoustic spectrum sensor adopt piezoelectric ceramic sensors as pressure sensing devices, so that the influence of noise can be reduced, and an effective signal is amplified by using an amplifier and a filter, so that the aerosol acidity detection effect with high precision and high signal-to-noise ratio is realized.
Referring to fig. 1 and 2, fig. 1 shows a side view of a photo acoustic cell for aerosol acidity detection, fig. 2 shows a perspective view of a photo acoustic cell for aerosol acidity detection, the photo acoustic cell comprising a housing 1, an optical window 3, an air inlet pipe 7, an air outlet pipe 8, a photo acoustic resonant cavity 10 penetrating the housing 1 and a piezo ceramic sensor 2 inside the housing 1, aerosol entering the photo acoustic resonant cavity 10 from the air inlet pipe 7 and being guided out from the air outlet pipe 8, the piezo ceramic sensor 2 being used for detecting photo acoustic signals of aerosol inside the photo acoustic resonant cavity. The laser light enters the photoacoustic cavity through an optical window.
It should be noted that, the connection part of the air inlet pipeline and the photoacoustic resonant cavity is subjected to flaring treatment to form a nozzle, so that collision loss of aerosol and the inner wall is reduced. Stainless steel valves can be arranged at pipeline openings of the air inlet pipeline and the air outlet pipeline to control closing.
Optionally, a cylindrical groove is formed in the shell, a fixing groove is formed in the cylindrical groove, and the piezoelectric ceramic sensor is installed in the cylindrical groove and is positioned by the fixing groove.
The cylindrical groove and the fixed groove are arranged according to the shape of the piezoelectric ceramic sensor, the piezoelectric ceramic sensor is arranged in the cylindrical groove, and the fixed groove is used for positioning, so that shaking can be reduced, and the accuracy of signal detection is improved. For example, the piezoelectric ceramic sensor is a cylinder with a diameter of 39mm and a height of 51mm, the cylindrical groove is designed to be 42mm in diameter and 48mm in height, and a fixing groove with a diameter of 39mm and a depth of 3mm is formed in the groove.
Optionally, deionized water or turpentine is filled in the gap between the cylindrical recess and the piezoceramic sensor to exclude air.
Referring to fig. 1, deionized water or turpentine is filled in the gap 6 between the cylindrical groove and the piezoelectric ceramic sensor to remove air, so that rapid attenuation caused by ultrasonic wave conduction in the air is reduced.
Optionally, the photoacoustic cell further includes a flange by which the piezoceramic sensor is secured to the housing and by which the optical window is secured to the housing, reducing evaporation of the conductive medium.
Referring to fig. 1, the photoacoustic cell further includes a flange 5, the piezoelectric ceramic sensor is fixed on the housing through the flange, and the optical window is fixed on the housing through the flange, so that the photoacoustic cell is firmer, shake is reduced, and accuracy of signal detection is improved.
Optionally, the material of the optical window comprises an infrared crystalline material comprising any one of magnesium fluoride, zinc sulfide, zinc selenide, sapphire, or silicon.
The infrared transmitting crystal material has the characteristics of high mechanical strength and good high temperature resistance, and the infrared transmitting crystal material comprises any one of magnesium fluoride, zinc sulfide, zinc selenide, sapphire or silicon.
In a specific embodiment, the optical glass window is a sapphire window sheet (not coated) having a light-transmissible wavelength of 200nm to 4.5 μm, the uncoated sapphire having excellent surface hardness, and the transmittance ranging from ultraviolet to mid-infrared wavelength region. Sapphire can only be scratched by a few substances other than it. Uncoated substrates are chemically inert and also insoluble in water, common acids or bases at temperatures up to about 1000 ℃. The sapphire window is a z-axis section, so that the c-axis of the crystal is parallel to the optical axis, and the birefringent effect of the transmitted light is eliminated. The optical window can form a closed space with the photoacoustic cell, and ensures that the light source enters the photoacoustic resonant cavity to generate a photoacoustic signal and outputs the photoacoustic signal from the other end. The sapphire optical window can basically meet the excitation light source in most wavelength ranges, so that the absorption of the window to laser energy is reduced, and the window noise is reduced.
Optionally, the material of the housing comprises any one of stainless steel, quartz or an aluminum alloy.
The photoacoustic cell housing 1 is made of an acid-base resistant, airtight and liquid-tight hard material and is used for accommodating standard solution and liquid drop aerosol, and the material comprises any one of stainless steel, quartz or aluminum alloy.
Optionally, the piezoceramic sensor comprises any one of a hydrophone, a tuning fork, or a miniature microphone.
The piezoelectric ceramic sensor is determined according to practical applications, and the present embodiment is not particularly limited, and includes, but is not limited to, any one of a hydrophone, a tuning fork, or a miniature microphone.
Optionally, the photoacoustic resonant cavity comprises a cylindrical or square shape.
The shape of the photoacoustic cavity is determined according to practical applications, and the present embodiment is not particularly limited, including but not limited to a cylinder or a square. In a specific embodiment, the photoacoustic cavity comprises a cylinder in shape with a photoacoustic cavity length of 50mm-150mm and a diameter of 5mm-15mm. Different resonant cavity diameters can be selected for light sources with different beam qualities, and the maximum photoacoustic signal is obtained under the condition that the background noise is unchanged. The length of the photoacoustic resonant cavity can meet different application environments, the influence of noise is reduced, and the signal-to-noise ratio is improved. Of course, a fixed resonant cavity can also be used as a non-resonant photoacoustic cell, and noise reduction and amplification treatment by a filtering device are needed at this time.
The photoacoustic cell can further comprise a sealing ring 4, and sealing rings can be arranged between the flange and the optical window and between the optical window and the port of the shell, and the sealing rings can enable the optical window and the flange to be well sealed with the port of the shell, so that a closed space is formed by the photoacoustic cell. The photoacoustic cell may also be a base support for supporting the entire device.
The design structure of the photoacoustic cell is simple, and all components are symmetrically distributed and are easy to process; the polishing treatment of the inner surface of the photoacoustic cavity reduces damping, is favorable for accumulation of photoacoustic signal energy in the cavity, and improves sensitivity by forming standing waves; meanwhile, the liquid drops are prevented from adhering to the surface of the inner wall to interfere with a sampling result.
The embodiment of the invention provides a system for detecting aerosol acidity, which comprises a laser light source, a chopper, an amplifier, an oscilloscope and the photoacoustic cell; wherein, the liquid crystal display device comprises a liquid crystal display device,
a laser light source for generating laser light and emitting the laser light to the chopper;
the chopper is used for modulating the incoming laser and transmitting the modulated laser into the photoacoustic resonant cavity of the photoacoustic cell;
the photoacoustic cell is used for collecting electric signals corresponding to acoustic-optical signals generated by aerosol in the photoacoustic resonant cavity;
an amplifier for amplifying the electrical signal;
and the oscilloscope is used for collecting the amplified electric signals.
Referring to fig. 3, the system for aerosol acidity detection includes a laser light source 11, a chopper 12, an aerosol generator 13, an amplifier 14, an oscilloscope 15, and a photoacoustic cell 16. The aerosol generator 13 is used for preparing an acidic solution into aerosol and filling the aerosol into a photoacoustic resonance cavity of the photoacoustic cell, light emitted by the laser light source 11 is modulated by the chopper 12 and then irradiates the photoacoustic cell 16, and a photoacoustic signal of the aerosol in the photoacoustic cell 16 is amplified and noise reduced by the amplifier and is acquired by the oscilloscope. The photoacoustic cell enables aerosols with different acidity to generate photoacoustic effects, and generates photoacoustic signals with different intensities.
The laser source can use a nanosecond laser, the generated 1064nm laser has high energy density, the generated photoacoustic signal is strong, and the generated photoacoustic signal is clearer.
The chopper can use an OE3001 optical chopper, accurately tracks an external trigger signal by adopting a high-precision phase-locked loop, and accurately drives a motor by adopting PID control and provides a stable reference output signal. OE3001 is composed of three major parts, the host case, the chopper mechanism, and the connecting wires. Wherein the main case is an electronic control system; the chopping machine comprises a chopping seat, chopping blades and the like, so that chopping action is realized; the main case controls the motor and reads the rotating speed of the motor through a connecting wire.
The amplifier can be an SR560 type low-noise amplifier, and can perform noise reduction and filtering processing while amplifying the photoacoustic signal, thereby improving the signal-to-noise ratio. The oscilloscope may be an MDO3034 type oscilloscope.
The photoacoustic cell adopts a resonant structure, and the acoustic pressure mode in the resonant cavity is a primary longitudinal standing wave mode, so that the accumulated photoacoustic energy is maximized in order to enable the photoacoustic signal to resonate with the resonant frequency of the resonant cavity, and an excitation light source needs to be modulated (> 1 kHz), so that the influence of 1/f noise can be reduced. The intensity of the photoacoustic signal can be improved by using the piezoelectric ceramic sensor and the nanosecond laser as the excitation light source, and the photoacoustic cell can be used as a non-resonant photoacoustic cell without modulating light at this time.
Referring to fig. 4, an embodiment of the present invention provides a method for detecting acidity of an aerosol, which is applied to the above system, and includes:
s100, preparing aerosol from the acidic solution through an aerosol generator, and filling the aerosol into a photoacoustic resonance cavity of the photoacoustic cell.
The liquid drop aerosol is generated by an aerosol generator, the compressed air is used for spraying gas from the tip to stir the standard solution to form aerosol with the diameter of about 2.5 mu m, and then the aerosol enters the photoacoustic resonance cavity along with the air flow for measurement. Since the aerosol is flowing throughout the process, the atmospheric environment is well simulated. In practice, atmospheric sampling requires pumping an atmospheric aerosol into a photoacoustic cell for detection.
S200, determining control parameters of the laser light source and the chopper, and starting the laser light source and the chopper.
It is noted that the signal amplitude is proportional to the laser power, the larger the signal amplitude. In practice, however, the larger the power of the laser is, the better. With the improvement of the output power of the laser, on one hand, saturation effect can occur, and the amplitude and the power of the measured signal are not in a linear relation; on the other hand, the quality of the laser beam can start to be poor, part of stray light can strike the wall of the photoacoustic cell cavity, and noise of the system is increased; it is therefore necessary to determine a more appropriate range.
S300, acquiring an electric signal through an oscilloscope, and determining the acidity of aerosol according to a standard curve and the acquired electric signal; the standard curve characterizes a relationship of known acidity and electrical signal.
Before aerosol detection, a standard curve needs to be measured by liquid phase detection, and standard solutions comprise sulfuric acid, sodium sulfate solution, ammonium sulfate solution, mixed solutions of the above solutions and the like, and the components of the liquid drop aerosol need to be consistent with the components of the standard curve. In the measuring process, the acidity of the aerosol is determined by comparing the collected electrical signals with a standard curve.
The embodiment of the invention has the following beneficial effects: the photoacoustic cell for detecting the acidity of the aerosol in the embodiment comprises a shell, an optical window, an air inlet pipeline, an air outlet pipeline, a photoacoustic resonant cavity penetrating through the shell and a piezoelectric ceramic sensor in the shell, wherein the aerosol enters the photoacoustic resonant cavity from the air inlet pipeline and is guided out from the air outlet pipeline, and the piezoelectric ceramic sensor is used for detecting a photoacoustic signal of the aerosol in the photoacoustic resonant cavity; the system for detecting the acidity of the aerosol comprises a laser light source, a chopper, an aerosol generator, an amplifier, an oscilloscope and a photoacoustic cell, wherein laser generated by the laser light source is modulated by the chopper and then is emitted into a photoacoustic resonant cavity in the photoacoustic cell, a photoacoustic signal of the aerosol is measured by a piezoelectric ceramic sensor, the photoacoustic signal of the aerosol is collected by the amplifier and the oscilloscope, and finally the acidity of the aerosol is determined according to the photoacoustic signal of the aerosol, so that the acidity of the aerosol is measured by a laser spectrum, and the accuracy of detecting the acidity of the aerosol is improved.
While the preferred embodiment of the present invention has been described in detail, the present invention is not limited to the embodiments, and those skilled in the art can make various equivalent modifications or substitutions without departing from the spirit of the present invention, and these equivalent modifications or substitutions are included in the scope of the present invention as defined in the appended claims.
Claims (10)
1. The photoacoustic cell for detecting the acidity of the aerosol is characterized by comprising a shell, an optical window, an air inlet pipeline, an air outlet pipeline, a photoacoustic resonant cavity penetrating through the shell and a piezoelectric ceramic sensor in the shell, wherein the optical window is respectively arranged at two ends of the boundary between the photoacoustic resonant cavity and the shell, the air inlet pipeline and the air outlet pipeline are respectively connected with two ends of the photoacoustic resonant cavity through the shell, and the piezoelectric ceramic sensor is arranged in the cross section direction of the photoacoustic resonant cavity; aerosol enters the photoacoustic resonant cavity from the air inlet pipeline and is guided out from the air outlet pipeline; the piezoelectric ceramic sensor is used for detecting the photoacoustic signal of the aerosol in the photoacoustic resonant cavity.
2. The photoacoustic cell of claim 1 wherein the housing is provided with a cylindrical recess having a retaining groove disposed therein and the piezoceramic sensor is mounted in the cylindrical recess and positioned using the retaining groove.
3. The photoacoustic cell of claim 2 wherein the space between the cylindrical recess and the piezoelectric ceramic sensor is filled with deionized water or turpentine to exclude air.
4. The photoacoustic cell of claim 1 further comprising a flange by which the piezoceramic sensor is secured to the housing and by which the optical window is secured to the housing.
5. The photoacoustic cell of claim 1 wherein the material of the optical window comprises an infrared crystalline material comprising any one of magnesium fluoride, zinc sulfide, zinc selenide, sapphire, or silicon.
6. The photoacoustic cell of claim 1 wherein the material of the housing comprises any one of stainless steel, quartz or an aluminum alloy.
7. The photoacoustic cell of claim 1 wherein the piezoceramic sensor comprises any one of a hydrophone, a tuning fork, or a miniature microphone.
8. The photoacoustic cell of claim 1 wherein the photoacoustic resonant cavity comprises a cylindrical or square shape.
9. A system for aerosol acidity detection comprising a laser light source, a chopper, an amplifier, an oscilloscope, and a photoacoustic cell according to any one of claims 1-5; wherein, the liquid crystal display device comprises a liquid crystal display device,
a laser light source for generating laser light and emitting the laser light to the chopper;
the chopper is used for modulating the incoming laser and transmitting the modulated laser into the photoacoustic resonant cavity of the photoacoustic cell;
the photoacoustic cell is used for collecting electric signals corresponding to acoustic-optical signals generated by aerosol in the photoacoustic resonant cavity;
an amplifier for amplifying the electrical signal;
and the oscilloscope is used for collecting the amplified electric signals.
10. A method for aerosol acidity detection, applied to the system of claim 9, comprising:
preparing aerosol from the acidic solution through an aerosol generator, and filling the aerosol into a photoacoustic resonance cavity of the photoacoustic cell;
determining control parameters of a laser light source and a chopper, and starting the laser light source and the chopper;
collecting an electric signal through an oscilloscope, and determining the acidity of the aerosol according to a standard curve and the collected electric signal; the standard curve characterizes a relationship of known acidity and electrical signal.
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