164 results about "Photoacoustic cell" patented technology

The invention relates to a portable SF6 gas resolvent photoacoustic spectrum detecting device and method which have the advantages of being high in sensitivity, capable of automatically achieving detection and concentration conversion, fast in detection speed, high in accuracy, easy to carry and suitable for online monitoring. A paraboloid column mirror is arranged in a casing, and an infrared source is arranged on the paraboloid column mirror. A chopper, an optical filter wheel and a photoacoustic cell are arranged in front of the paraboloid column mirror, and a plurality of optical filters are evenly distributed on the optical filter wheel along the circumferential direction. The photoacoustic cell comprises a microtone device, an air pressure sensor and a temperature sensor and connected with an air pipe and a vacuum pipeline which is connected with a vacuum pump. The chopper is connected with a chopper controller, the optical filter wheel is connected with a singlechip microcomputer, the microtone device is connected with a phase-locking amplification module, the air pressure sensor is connected with the singlechip microcomputer, the temperature sensor is connected with an analog/digital (A/D) converter which is connected with the phase-locking amplification module, and the singlechip microcomputer is further connected with a liquid crystal driving and display screen and a working power source.

The invention relates to an intrinsic safety opto-acoustic spectrum gas monitoring system based on an optical acoustic sensor. The Intrinsic safety opto-acoustic spectrum gas monitoring system comprises a light source device which is connected with a photoacoustic cell device through optical fibers and an optical fiber collimator, and the incident direction of laser emitted from the light source is collinearly aligned with the axle center of the photoacoustic cell device; and phase-shifting erbium-doped grating optical fiber with the 1/4 wavelength of the optical acoustic sensor is annularly paved on the inner wall of the photoacoustic cell device, the photoacoustic cell device is communicated with a gas to be tested, and the grating optical fiber is connected with a demodulation device and a data acquisition device. The invention has the advantages of high detection sensitivity, fast response speed, and the like and can realize fast, accurate and long-term on-line monitoring of trace toxic and harmful gases or other specific gases, in particular to accurate measurement and analysis of gases under some special detection environments, such as the strong electromagnetic environment, the radioactive environment, the environment in a gas-production coal mine which is not allowed to use a power supply device on site, and the like.

The invention discloses a cantilever beam and photoacoustic cell double-resonance enhanced-type photoacoustic spectrum detection system and a method, and belongs to the technical field of trace gas detection. According to the cantilever beam and photoacoustic cell double-resonance enhanced-type photoacoustic spectrum detection system and the method, sound wave generated by excitation of gas molecules with a light source is subjected to coherence stack in an acoustic resonance tube of a resonant photoacoustic cell, so that photoacoubtic signal amplitude is increased effectively; at the same time, fine adjustment on the photoacoustic cell resonant frequency is realized through precise design and temperature control of a cantilever beam structure, so that accurate matching of the cantilever beam resonant frequency with the photoacoustic cell resonant frequency is realized, and the photoacoubtic signals are enhanced further via one step resonant of the cantilever beam; the double-resonanceenhanced-type photoacoustic spectrum method is combined with a phase-locked amplifier to realize super sensitive gas detection. The double-resonance enhancing effect of the cantilever beam and the photoacoustic cell is capable of realizing obvious amplification of photoacoubtic signals, the system working frequency is controlled at kHz order of magnitude, 1/f noise is reduced greatly, and a technological scheme with competitiveness is provided for super low concentration gas detection.

The invention discloses a membrane-type minitype photoacoustic cell and an application thereof. The membrane-type minitype photoacoustic cell and the application thereof are characterized in that the membrane-type minitype photoacoustic cell is provided with a cylinder body, a vibration sensing thin film is arranged at one end of the cylinder body, an optical fiber is plugged into the other end of the cylinder body, and a cylindrical photoacoustic cavity is formed. An airflow through-hole is arranged on the lateral wall of the cylinder body, the detection light and the exciting light modulated by audio frequency signals are transmitted through the optical fiber. The membrane-type minitype photoacoustic cell has a miniaturized volume, the detection sensitivity is high, the photoacoustic detection is in an all-optical structure, and the membrane-type minitype photoacoustic cell can be used for gas concentration detection under inflammable and explosive circumstances.

The invention discloses a method for simultaneously measuring an absorption coefficient of an aerosol at multiple wavelengths through a single photoacoustic cell. The method comprises the steps that amplitude modulation is conducted on multiple laser devices with different wavelengths through square signals which are generated by a function generator at the frequency intervals of df, lasers with different wavelengths are emitted into the photoacoustic cell after being subjected to beam combination through a fiber optic combiner, the lasers emitted into the photoacoustic cell interact with the aerosol in the photoacoustic cell, and a photoacoustic signal P<m>(f0+/-f) reflecting an absorption signal of aerosol particles is generated; the absorption coefficient of the aerosol at the multiple wavelengths is obtained through calculation according to a deduced absorption coefficient formula at different modulation frequencies. The method solves the problems of spatial and temporal heterogeneity of samples and particle losses caused by measurement conducted through multiple photoacoustic cells, the measuring process is simpler, and the system structure is more compact. By means of the method, the aerosol absorption Angstrom coefficient can be obtained, components of the aerosol can be recognized, and therefore a valuable decision making basis is provided for traceability and governance of haze.

Modular photoacoustic detection device comprising:

• • a photoacoustic cell including at least two chambers connected by at least two capillaries and forming a Helmholtz type differential acoustic resonator;
  • acoustic detectors coupled to the chambers;
  • a light source capable of emitting a light beam having at least one wavelength capable of exciting a gas intended to be detected and which can be modulated to a resonance frequency of the photoacoustic cell;
  • a first photonic circuit optically coupling the light source to an input face of a first of the chambers;

wherein the first photonic circuit is arranged in a detachable manner in a first housing formed in the acoustic cell and emerging on the input face of the first chamber.

The invention provides a scanning laser interference type fiber optic acoustic phase-locked detection system and a scanning laser interference type fiber optic acoustic phase-locked detection method,which belong to the technical field of trace gas detection. The system comprises a photoacoustic excitation light source, a light modulator, a photoacoustic cell, a fiber optic microphone, a broad-band scanning laser source, a fiber optic circulator, a high-speed wavelength query module, a phase-locked loop, a square-wave signal generator, a digital signal processor, and a computer. By carrying out synchronous wavelength scanning control and synchronous spectrum sampling control on the broad-band scanning laser source and the high-speed wavelength query module and combining the Fabry-Perot cavity length high-speed synchronous demodulation technique based on a fiber optic scanning laser interferometer with the phase-locked amplification technique, the invention realizes high sensitivity andhighly stable detection on weak photoacoustic signals. The invention can greatly increase the precision and limit sensitivity of photoacoustic spectrometry-based trace gas detection, and provides a highly competitive technical solution for photoacoustic spectrometry-based trace gas detection.

The invention relates to the field of fruit ripeness testing and particularly relates to a fruit ripeness nondestructive testing system and method based on an infrared photoacoustic spectrum. The invention aims at solving the problem of interference of light scattering and reflection in a near infrared spectrum testing method so as to improve the testing accuracy. The testing system comprises a laser emission component, a photoacoustic detection component and a signal processing component, wherein the laser emission component comprises a laser signal modulation device, a laser controller and an infrared laser; the photoacoustic detection component comprises an optical splitter, a reference photoacoustic cell, a sample photoacoustic cell and a photoacoustic detector; and the signal processing component comprises a microcontroller, a pre-amplifier and a phase-locked amplifier. The invention has the following beneficial effects: the fruit quality is judged by adopting the infrared laser photoacoustic spectrum to test the ethylene gas emitted by fruits, and then the fruit ripeness is judged according to the content of the ethylene gas emitted by the fruits; and moreover, the interference of light scattering and reflection in the near infrared spectrum testing method is avoided, and thus the testing accuracy is improved.

The invention discloses a detection device and method of detecting ammonia gas by utilizing a photo-acoustic spectroscopy method. The detection device comprises a light source, a chopper, an optical filter, a photoacoustic cell, a micro-silicon microphone and an infrared detector; the chopper is arranged in parallel in front of the photoacoustic cell; the optical filter is arranged at the left end of the photoacoustic cell; the photoacoustic cell is divided into an upper air chamber and a lower air chamber; the infrared detector is embedded in the right end of the air chamber at the upper part; the micro-silicon microphone is embedded in the right end of the air chamber at the lower part; the infrared detector and the micro-silicon microphone are arranged on a same vertical plane; and light from the light source is input into the optical filter and filtered by the optical filter and then enters the photoacoustic cell after being subjected to wave chopping by the chopper. According to the detection device and method, the photoacoustic cell is divided into the upper air chamber and the lower air chamber, and the micro-silicon microphone and the infrared detector are arranged in parallel on the same side of the upper air chamber and the lower air chamber from top to bottom respectively, so that the micro-silicon microphone and the infrared detector carry out detection at the same time; and on signal detection, the micro-silicon microphone and the infrared detector generate signals in the same light source and a gas cavity at the same time, and interference is calculated and rejected, so that a final concentration result is more accurate.

The invention provides a method for realization of online calibration of photoacoustic spectroscopy system pool constants by use of oxygen in atmosphere, and relates to the method for realization of online calibration of the photoacoustic spectroscopy system pool constants. Part of light emitted by a laser emits into a wavemeter by a beam splitter prism, and another part of the light emitted by the laser emits into a photoelectric detector by an electro-optic intensity modulator and a photoacoustic cell, the photoelectric detector inputs into a computer; an atmosphere flow enters into the photoacoustic cell, a microphone picks up photoacoustic signals to input into the computer; the computer calculates to obtain system constants by combination of collected data and atmospheric oxygen concentration and absorption coefficients, and the like. The method solves the technical problems of uncertainty and inconvenient use brought by the fact that a gas detection instrument in the prior art needs calibration by use of a standard gas. The beneficial effects of the method are that: by use of the known and relatively stable characteristics of the atmospheric oxygen concentration for calibration, uncertainty brought by the standard gas can be avoided, and the on-line calibration function can be realized. The operation is convenient, the calibration is accurate, and the method provides the reliable theoretical basis for online calibration of a photoacoustic spectroscopy system.

The invention discloses a system used for detecting gas in transformer insulating oil, and belongs to the field of electrical equipment. The system used for detecting gas in transformer insulating oil comprises: a light source module, a chopper module, a photoacoustic cell module, a signal processing module, and a controller module which are connected by signals. The chopper module comprises a chopper; the chopper comprises a motor drive circuit, a motor, a raster encoder code wheel, a Hall sensor and a display screen; the motor drive circuit receives control instruction of the controller module by serial port communication, and control the motor to rotate according to the control instruction; the raster encoder code wheel is connected with a front shaft of the motor; and the Hall sensor is connected with a back shaft of the motor. A combination structure formed by a semiconductor laser and an optical filter is applied in the light source module; a resonant photoacoustic cell structure is applied in the photoacoustic cell, and lock-in amplifier technologies are applied in the signal processing module. The control module is used for system control and calculation of gas concentration. The system used for detecting gas in transformer insulating oil has advantages of fast detecting speed, high detecting accuracy and excellent user-machine interactivity.

The invention discloses a laser photoacoustic spectrometry device for measuring multi-component gas by adoption of a single photoacoustic cell. The device comprises a stop valve (1), a particulate matter filtering device (2), a gas drying device (3), an electromagnetic switching valve I (4), a pressure sensor (5), an electromagnetic switching valve II (6), a sound velocity nozzle (7), a vacuum pump (8), a quantum cascading laser array module (9), a spectroscope module (10), a to-be-measured reference gas chamber (11), a differential resonance photoacoustic cell (12), a photoelectric conversionmodule (13), a thermostat (14), an optical power detector (15), an extinction pool (16), a phase-locked amplification circuit (17) and an industrial personal computer (18), wherein the quantum cascading laser array module (9) couples multiple beams of laser into one beam of light path. According to the device, multiple faulty gas components can be measured by the single photoacoustic cell at thesame time. The device has the advantages of being strong in anti-jamming capability, good in long-term stability of equipment, high in precision and free of later maintenance, and is capable of measuring trace gas to gas with a concentration of 100%.

The invention provides a photoacoustic spectroscopy oil gas detecting device capable of eliminating cross interference. The device comprises a degassing module and a photoacoustic spectroscopy detecting module, wherein the photoacoustic spectroscopy detecting module mainly comprises a photoacoustic cell, an infrared thermal radiation pulse light source, a filter wheel, a semiconductor laser, a photodetector and a microphone. The device sends oil gas desorbed from the degassing module into the photoacoustic spectroscopy detecting module, the concentration of methane is detected by adopting thesemiconductor laser through using the principle of photoacoustic spectroscopy, and the infrared thermal radiation pulse light source is adopted to detect other fault gases. The device can eliminate the cross interference caused by the overlap of methane and ethane absorption spectrum bands and improve the measurement accuracy of methane and ethane.

The invention discloses a photo-acoustic spectrum gas detecting system based on a distributed feedback optical fiber laser, belonging to the gas detection technologies. The photo-acoustic spectrum gas detecting system comprises a coherent light source, a distributed feedback optical fiber laser and the like, wherein the coherent light source is connected with a modulator through a self-supplied tail fiber, and the modulator is connected to a photoacoustic cell through a common optical fiber to form a sound signal excitation optical path; a 980 pump semiconductor laser is connected with a 980nm end of a wavelength division multiplexer through the tail fiber to form a detection optical path with a subsequent optical path. The invention is characterized in that the distributed feedback optical fiber laser is used as a sensor for probing sound and fixed in the photoacoustic cell, and one end thereof is connected to a common end of the wavelength division multiplexer through the common optical fiber; an 1550nm end of the wavelength division multiplexer is connected with an isolator; an output end of the isolator is connected with a wavelength demodulation system of the far end through the common optical fiber. The photo-acoustic spectrum gas detecting system can be normally used in the environment of strong electromagnet and radioactivity, can be used for detecting a special gas environment, and is convenient for forming a network by multiplexing a plurality of the systems so as to realize remote monitoring of multiple points.

The invention discloses a photoacoustic spectrometry and chromatography spectrometer for trace gas in insulating oil and an analysis method. The photoacoustic spectrometry and chromatography spectrometer for the trace gas in the insulating oil and the analysis method are characterized by adopting a photoacoustic spectrometry and chromatography hyphenated technology method to analyze seven component bodies of oil dissolved gas: hydrogen, oxygen, carbon monoxide, methane, ethylene, ethane and acetylene. A complete machine system adopts a double- chromatographic-column separation system, utilizes a ten-way valve to switch over, and uses a non-split sampling manner; all samples enter a first chromatographic column at a time, after the hydrogen, the oxygen, the carbon monoxide and the methane come out, the ten-way valve is switched to a second chromatographic column, and the ethylene, the ethane and the acetylene continuously appear. The components in samples flow into a photoacoustic cell detection module after flowing out, and are detected by adopting a photoacoustic spectrometry technology. According to the instrument, samples are fed at a time, the seven component dissolved gases are analyzed, each gas is firstly separated and then detected, the cross sensitivity is avoided, the sensitivity is high, and the photoacoustic spectrometry and chromatography spectrometer has excellent sensitivity on each component key gas, especially the acetylene, and is suitable to be popularized and used in smart power grid projects.

The invention discloses a photoacoustic spectrometry oil and gas monitoring unit which comprises a photoacoustic cell, wherein a temperature adjusting semiconductor is arranged in a laser, and a gas inlet is formed in a photoacoustic cell body; a sound-sensitive element which is used for detecting the pressure wave generated in the photoacoustic cell and outputting an output signal of the sound-sensitive element; a signal processing circuit which is used for processing a signal output by the sound-sensitive element; a central processing unit which is used for analyzing the signals, receiving the signals and sending instructions, wherein the central processing unit is externally connected with a power supply circuit; a laser driving circuit which is used for controlling the laser to generate laser with a specific wavelength. The wavelength of laser emitted by the laser in the monitoring unit is easy to control and can be easily enabled to change periodically, deviation of a finally obtained spectrogram is prevented, detection precision is improved, signals led out by the sound-sensitive element are subjected to multi-stage processing, the detection precision is further improved, andthe acoustic spectrum oil and gas monitoring unit is sensitive and high in accuracy.

The invention discloses an off-resonance dual-cavity photoacoustic cell used in noninvasive blood glucose measurement and a detection method. The off-resonance dual-cavity photoacoustic cell includes a sample cell, an incidence window, a laser, a communicating pipe, an inspection room, an adjusting plate and a microphone, wherein a to-be-detected sample is placed in the sample cell; a gas cavity is formed by the space from the upper surface of the to-be-detected sample to the incidence window; the incidence window is installed at the top of the sample cell; the laser is arranged on the incidence window; the communicating pipe is arranged on the lateral surface of the sample cell and faces to the gas cavity; the inspection room is placed at the rear end of the communicating pipe and forms a detection cavity together with the adjusting plate; and the detection cavity is mutually communicated with the gas cavity through the communicating pipe. As the position of the adjusting plate in the inspection room is adjustable, the volume of the detection cavity can be changed to adapt to different modulating frequencies; and the microphone installed on the adjusting plate is used for detecting the intensity of the optical and acoustic signals. The off-resonance dual-cavity photoacoustic cell and the method solve the disadvantages that the traditional resonance type photoacoustic cell has big volume, is difficult to process and manufacture and is only suitable for single stationary modulating frequency, and can meet the requirement of blood glucose monitoring.

The invention relates to a detection instrument and method for a reinforced laser photoacoustic spectrometry of a small-sized multi-reflection photoacoustic cell, which belongs to the technical fieldof trace gas detection. The detection instrument comprises a laser light source, a light source drive, an optical collimator, a small-sized multi-reflection photoacoustic cell, an air inlet valve, anair outlet valve, a microphone, a signal acquisition and processing circuit and a touch screen. The wavelength modulation is performed for the laser light source, and the laser is reflected for multiple times on the wall surface of the small-sized multi-reflection photoacoustic cell along a radial direction. By adopting a secondary resonant detection technology, the interference of a fundamental-frequency photoacoustic signal generated by a solid photoacoustic effect due to the multiple reflection on the wall surface can be eliminated, and the background-free and high-sensitivity detection fortrace gas can be realized. By adopting the small-sized multi-reflection photoacoustic cell in the detection instrument, while the capacity in the cell can be reduced, the active power of the photoacoustic exciting light can be greatly increased by virtue of the multiple reflection of the laser on the inner wall, so that the requirement on the gas sample amount can be reduced, and the detection sensitivity and stability of the system can be improved.

The invention discloses a photoacoustic gas detecting method and a photoacoustic gas detecting device capable of reducing the environmental noise. An external microphone is arranged outside a photoacoustic cell, and the signal detected by the external microphone is used for correcting the environmental noise in the signal detected by an internal microphone arranged inside the photoacoustic cell, thus the environment adapting ability of the photoacoustic gas detecting device can be strengthened, and the precision and the reliability the photoacoustic gas detecting device can be improved. The noise signal detected in the internal microphone is calibrated by the external microphone, thus the noise signal which has the same frequency and the same phase as the photoacoustic signal in the internal microphone can be eliminated, the influence of the outside noise to the precision of the photoacoustic gas detecting device can be effectively reduced, the environment adapting ability of the photoacoustic gas detecting device can be strengthened, and the photoacoustic gas detecting device can be miniaturized.

The invention relates to a device and a method for correcting a secondary harmonic waveform of a photoacoustic system and increasing precision and belongs to the field of gas sensing detection of optical fibers. The device comprises an DFB laser, a temperature control module, single chips, a signal generator, a photoacoustic cell, a microphone, a pre-amplifier and a lock-in amplifier; the two single chips are used for respectively generating a zigzag wave and an anti-aliasing wave as scanning signals; output ends of the single chips and signal generator are connected with an input end of a summator; the output end of the summator is connected with the DFB laser; the temperature control module is used for controlling the DFB laser to adjust the middle position of the gas absorption peak wavelength in a scanning signal cycle; the light emitted from the DFB laser enters into the photoacoustic cell; the microphone is placed on a microphone fixing position and is used for detecting the acoustic wave; the output end of the microphone is connected with the input end of the pre-amplifier; the output end of the pre-amplifier is connected with the input end of the lock-in amplifier; a computer is connected with the output end of the lock-in amplifier. A secondary harmonic wave signal with two symmetric lower peak valleys is acquired on the computer and the detecting precision is increased.

The invention discloses an acoustic transmission line model of a one dimensional vertical resonant cavity for detecting the decomposition product of sulfur hexafluoride. The model is established by the following steps: step one, simulating the finite element of a photoacoustic cell; step two, establishing an acoustic transmission line model of a photoacoustic signal; step three, establishing an oscillating circuit model of a one dimensional vertical photoacoustic cavity; and step four, analyzing and processing the acoustic transmission line model and the oscillating circuit model. The providedacoustic transmission line model has the advantages that a photoacoustic signal is enhanced through resonance, the cavity does not need to be sealed; the influence of low frequency noise can be effectively inhibited by high modulation frequency, the signal-noise ratio is better; the resonance photoacoustic cavity has the characteristics of simple manufacturing, practicality, and high sensitivity;finite element analysis of a photoacoustic cell is combined to simplify the conventional acoustic transmission line theory; a LC oscillating circuit transmission line module for a one dimensional vertical photoacoustic cavity is established so that the acoustic parameters of the photoacoustic cavity can be analyzed rapidly and visually, and theoretical guidance is provided for the designing and manufacturing of a photoacoustic cell.

The invention relates to a photoacoustic cell of a modularized structure and suitable for laser photoacoustic spectrum detection. The photoacoustic cell comprises a photoacoustic cell casing with a main resonant cavity, a gas inlet, a gas outlet, an accommodating groove for placing a rheomicrophone, a sound hole for communicating the accommodating groove with the main resonant cavity, a light inlet and a light outlet, windows are fixed in the light inlet and outlet respectively, the two transverse sides of the photoacoustic cell are detachably connected with range extending modularized assemblies respectively, and the free ends of the two range extending modularized assemblies are detachably connected with end caps respectively; each range extending modularized assembly is composed with range-extending resonant cavity bodies distributed coaxially and connected deteachably, each range-extending resonant cavity body is internally provided with range-extending resonant cavity communicatedwith the main resonant cavity and penetrating the range-extending resonant cavity body in the traverse direction, and the range-extending resonant cavities and the main resonant cavity are the same in radius and distributed coaxially. The total length of the resonant cavity can be adjusted flexibly according to requirement of the measurement environment, the cell constant of the photoacoustic cell can be also adjusted, and thus, the photoacoustic signal intensity and detection system sensitivity are improved.

The invention discloses a device for detecting dissolved gas in transformer oil. The device comprises a power supply used for power supply, a main controller used for controlling, a chopper filter module, a photoacoustic detector and a laser assembly; the chopper filter module comprises an infrared source, a chopper modulating disc and a filter disc; the photoacoustic detector comprises a photoacoustic cell used for enabling detected gas to generate photoacoubtic signals under irradiation stimulation of specific-wavelength light; the laser assembly comprises a laser used for emitting single-wavelength laser. By the laser light source, interference of other gases on C2H2 gas high in specification can be avoided, and accuracy and flexibility in detection are quite high due to high light energy of the light source; meanwhile, other components (such as C2H4, C2H6, CH4, CO and CO2) of the dissolved gas of a transformer can be detected, and detection requirements of an electrical power system on the transformer oil can be met. The device is relatively simple in light path structure and lower in cost than that of double-laser light source, and more gas components are detected.

The invention discloses a gas detection system based on an open-type photoacoustic resonant cavity, and the system comprises: a light source module which is used for generating incident light; an opentype photoacoustic resonant cavity that is connected with the light source module and is provided with a ventilation window so as to enable gas to be detected to enter the cavity, and the open type photoacoustic resonant cavity is used for irradiating the gas to be detected in the cavity according to the incident light so as to generate a photoacoustic signal; and a signal processing module thatis connected with the open type photoacoustic resonant cavity and is used for converting the photoacoustic signal into an electric signal and processing the electric signal so as to finish the detection of the gas to be detected. According to the gas detection system based on the open type photoacoustic resonant cavity, the open type resonant photoacoustic cell is used, an optical lens does not need to serve as a window, the problem that background noise is generated due to the interaction of an optical window and a laser light source in an existing closed type photoacoustic cell is solved, and the sensitivity and accuracy of gas detection are improved.