Abstract: A photoacoustic gas sensor device for determining a value indicative of a presence or a concentration of a component in a gas comprises a measurement cell enclosing a measurement volume and a gas permeable area in the measurement cell for a gas to enter the measurement volume. An electromagnetic radiation source is arranged to emit electromagnetic radiation into the measurement volume, and a pressure transducer is arranged to measure a sound wave generated by the component in response to an absorption of electromagnetic radiation by the component in the measurement volume. In one aspect, the gas permeable area is represented by a porous gas permeable membrane with an average pore size of the porous gas permeable membrane between 10 nm and 1 ?m. In another aspect the gas permeable area is represented by an area of the measurement cell containing holes reaching through an otherwise gas tight material of the measurement cell, with a diameter of the holes between 100 nm and 10 ?m.

Abstract: The invention is a device and method for detecting an analyte in a medium. An exciting light source produces an exciting light wave, which propagates to the medium and heats the latter. The device comprises a transducer for detecting the heating of the medium. According to one embodiment, the transducer is a thermal transducer, configured to detect a variation in the temperature of the medium. According to another embodiment, the transducer is an acoustic transducer, configured to detect a photoacoustic wave propagating from the medium. Whatever the embodiment, the transducer employs a membrane, on which a waveguide is placed. The waveguide comprises a resonant optical cavity. Transduction is achieved by analyzing a variation in a resonant wavelength of the optical cavity.

Abstract: A series of optical spectral sensors for gas and vapor measurements using a combination of solid-state light sources (LED or Broadband) and multi-element detectors, housed within an integrated package that includes the interfacing optics and acquisition and processing electronics. The sensor is designed to be produced at a low cost and capable of being fabricated for mass production. Spectral selectivity is provided by a custom detector eliminating the need for expensive spectral selection components. A multi-component gas monitor system may have no moving parts and the gas sample flows through a measurement chamber where it interacts with a light beam created from the light source, such as a MEMS broad band IR source or a matrix of LEDs. A custom detector(s) is/are configured with multi-wavelength detection to detect and measure the light beam as it passes through the sample within the measurement chamber.

Abstract: The present disclosure discloses a degassing-free underwater dissolved carbon dioxide detection device and a detection method. The degassing-free underwater dissolved carbon dioxide detection device includes a computer, which is used to provide the driving signal and controlling parameters for the power tuning unit; the computer is connected with a laser driving control module and the power tuning unit, respectively; the laser driving control module is connected with a laser; the laser is connected with a photo-isolator; the photo-isolator is connected with a thulium-doped fiber vertical-cavity laser system; the thulium-doped fiber vertical-cavity laser system is connected with a photoacoustic cell system through a fiber collimator; the photoacoustic cell system is connected with a pre-amplifier circuit and a lock-in amplifier in sequence, and the lock-in amplifier is connected with the computer.

Abstract: The invention relates to a device for detecting a gaseous species by photoacoustic effect. The device comprises a substrate, inside which a cavity is formed. A light source is disposed on the substrate, in such a way that a part of the substrate extends between the light source and the cavity. The device is arranged in such a way that the light, emitted by the light source, is propagated through the substrate, before reaching the cavity.

Abstract: The invention relates, in a first aspect, to a photoacoustic spectroscope for analyzing gas, comprising an infrared emitter (3), which can be modulated, an analysis volume (1), which can be filled with gas, and a sound pressure detector. The sound pressure detector comprises a structure (5) capable of vibrating, an actuator and a measurement unit, wherein the actuator is configured to actively excite vibration of the structure (5) capable of vibrating and the measurement unit can measure the vibration properties of the structure (5) capable of vibrating, which measurement depends on the formation of the sound pressure waves.

Abstract: In an embodiment a beam-guiding cavity structure includes at least one first curved surface, one second curved surface and one third curved surface spanning a cavity, the first-third curved surfaces respectively having at least one first focal point and one second focal point, wherein the cavity is configured such that substantially no distance is laterally formed between the first focal point of the first curved surface and the second focal point of the second curved surface, wherein the cavity is further configured such that substantially no distance is laterally formed between the first focal point of the second curved surface and the second focal point of the third curved surface, wherein the first focal point of the second curved surface is arranged next to a connecting line of the first and second focal points of the first curved surface, wherein the first focal point of the third curved surface is arranged next to a connecting line of the first and second focal points of the second curved surface, and

Abstract: A series of optical spectral sensors for gas and vapor measurements using a combination of solid-state light sources (LED or Broadband) and multi-element detectors, housed within an integrated package that includes the interfacing optics and acquisition and processing electronics. The sensor is designed to be produced at a low cost and capable of being fabricated for mass production. Spectral selectivity is provided by a custom detector eliminating the need for expensive spectral selection components. A multi-component gas monitor system may have no moving parts and the gas sample flows through a measurement chamber where it interacts with a light beam created from the light source, such as a MEMS broad band IR source or a matrix of LEDs. A custom detector(s) is/are configured with multi-wavelength detection to detect and measure the light beam as it passes through the sample within the measurement chamber.

Abstract: A photoacoustic sensor includes a first layer with an optical MEMS emitter; a second layer stacked over the first layer with a MEMS pressure pick-up and an optically transparent window, wherein the MEMS pressure pick-up and the optically transparent window are offset laterally with respect to one another; and a third layer stacked over the second layer with a cavity for a reference gas. The optical MEMS emitter transmits optical radiation along an optical path, wherein the optical path runs through the optically transparent window and the cavity for the reference gas, and wherein the MEMS pressure pick-up is outside the course of the optical path.

Abstract: An apparatus and method of operating an atomic force profiler (AFP), such as an AFM, using a feedforward control signal in subsequent scan lines of a large area sample to achieve large throughput advantages in, for example, automated applications.

Abstract: The present disclosure relates to a photoacoustic gas sensor for detecting the presence or absence of gas using the interaction of a laser beam and gas molecules. The integrated photoacoustic gas sensor according to an embodiment includes a light output unit; a lens unit configured to concentrate a laser beam output from the light output unit; and a photoacoustic sensing unit having a quartz tuning fork aligned on the lens unit and configured to convert a vibration, generated when the laser beam passing through the lens unit interacts with gas molecules, into an electric signal.

Abstract: A photoacoustic measurement setup having an infrared radiator that is suitable for radiating broadband light with periodically modulated energy/intensity. The infrared radiator is configured to change an excitation spectra of a radiated broadband light, and a gas volume is heated by the radiated broadband light to generate an acoustic wave within the gas volume. The photoacoustic measurement setup also includes an acoustic sensor, which is suitable for measuring the acoustic wave generated in the gas volume.

Abstract: A light emitting structure for a photo-acoustic spectroscopy sensing device for sensing a target gas comprises a light source configured for emitting light of an input wavelength. The light emitting structure further comprises a conversion structure that is configured for absorbing light of the input wavelength, and that is further configured for emitting light of an output wavelength. The output wavelength of the conversion structure is adapted to an absorption wavelength of the target gas. The conversion structure comprises an output conversion layer that comprises a plurality of nanoparticles. The nanoparticles of the output conversion layer are configured for emitting light of the output wavelength.

Abstract: A downhole fluid analysis system includes an optical sensor that includes a light source configured to emit light, a light detector, and an optical tip optically coupled to the light source and the light detector. At least a portion of the light emitted from the light source travels through the optical tip and returns to the detector, wherein the optical tip has a bi-conical shape. The system further includes a piezoelectric helm resonator, in which the piezoelectric helm resonator generates a resonance response in response to an applied current, and an electromagnetic spectroscopy sensor positioned symmetrically with respect to the piezoelectric helm resonator in at least one direction. In some embodiments, the optical tip includes a first conical portion and a second conical portion.

Abstract: Various embodiments may relate to an optical device. The device may include an elongate substrate, an emitter portion at a distal end portion of the elongate substrate, the emitter portion configured to emit light, and an actuator portion at a proximal end portion of the elongate substrate opposite the distal end portion of the elongate substrate. The emitter portion may include a first electrode, a second electrode, and an active layer between the first electrode and the second electrode so that the light is emitted due to an increase in a temperature of the active layer upon application of a first potential difference between the first electrode and the second electrode. The active layer may be patterned to form a photonic crystal layer for enhancing directionality of the emitted light.

Abstract: A system and method for performing tissue therapy may include applying a reduced pressure to a tissue site of a patient. A fluid parameter associated with applying a reduced pressure to the tissue site may be sensed. An audible fluid leak location sound may be generated in response to sensing the fluid parameter. The audible fluid leak location sound may be altered in response to sensing that the fluid parameter changes. By altering the audible fluid leak location sound in response to sensing a change of the fluid parameter, a clinician may detect location of a fluid leak at the drape by applying force to the drape. The force applied to the drape may be a clinician pressing a finger onto an edge of the drape.

Abstract: A photoacoustic gas sensor includes a hermetically sealed housing filled with a reference gas. The photoacoustic gas sensor furthermore includes a microphone arranged in the housing and configured to generate a microphone signal as a function of a sound wave based on light incident in the housing. Furthermore, the photoacoustic gas sensor includes a controllable heat source arranged in the housing and configured to selectively thermoacoustically excite the reference gas in order to generate a thermoacoustic sound wave phase-shifted with respect to the sound wave.

Abstract: The present disclosure relates to a gas analyzer for measuring density and/or viscosity of a medium. The gas analyzer includes a connection panel having first and second media openings, each of which extends from a first surface to a second surface of the connection panel. A sensor panel is joined together with the connection panel on a first joint plane, and a cover panel is joined together with the sensor panel on a second joint plane, on a sensor panel face facing away from the connection panel. The cover panel has a cover panel cavity which communicates with the first and second media openings, and the sensor panel has at least one oscillator cavity which communicates with the first and second media openings. The sensor panel has a micromechanical oscillator arranged in the oscillator cavity and excitable to mechanically vibrate perpendicularly to the joint planes.

Abstract: The present invention relates to a sensor wiring substrate in which a decrease in detection accuracy is suppressed, a sensor package, and a sensor device. A gas sensor wiring substrate includes a substrate having a first accommodation recessed portion for accommodating a microphone element and a second accommodation recessed portion for accommodating an infrared light emitting element, and connection wiring. In the gas sensor wiring substrate, thermal resistance of a heat transfer path between a bottom surface of the first accommodation recessed portion and a bottom surface of the second accommodation recessed portion is greater than thermal resistance in any position of an imaginal heat transfer path in case of a depth of the first accommodation recessed portion identical with a depth of the second accommodation recessed portion. For example, the depth of the second accommodation recessed portion is deeper than the depth of the first accommodation recessed portion.

Abstract: An apparatus and method of operating an atomic force profiler (AFP), such as an AFM, using a feedforward control signal in subsequent scan lines of a large area sample to achieve large throughput advantages in, for example, automated applications.

Abstract: A method for analyzing particles includes concentrating the particles in an interior region of an air stream, generating a thermal gradient to deflect the concentrated particles from the interior region of the air stream to a peripheral region of the air stream, receiving orientation information, and adjusting the thermal gradient in response to the received orientation information. The particles may be concentrated in the interior of the air stream with at least two heater elements positioned near a periphery of the air stream and configured to cooperatively force particles away from the periphery and towards the interior region of the air stream. The orientation information may include gravity vector component information or angular rate component information in one, two or three substantially orthogonal directions relative to the air stream. Various systems for airborne particle detection with orientation-dependent particle discrimination are disclosed.

Abstract: A system for analyzing particles in an air stream includes a first heater element configured to deflect particles in an interior region of the air stream towards a peripheral wall of an air channel encompassing the air stream, a second heater element controllable to deflect the particles in a first lateral direction along the peripheral wall, and a third heater element controllable to deflect the particles in a second lateral direction along the peripheral wall. Thermal gradients in the air channel generated by the heater elements may thermophoretically force particles towards the peripheral wall in a direction perpendicular to the air stream to allow thermophoretic forcing and scanning of particles in either the first lateral direction or the second lateral direction along the peripheral wall and onto a surface of a particle detector. Systems and methods for scanning particles with thermophoretic forces are disclosed.

Abstract: The present invention provides a system for measuring concentrations of trace gases in gas mixtures using an absorption spectroscopy method. The system comprising: a resonant optical cavity containing a gas mixture, a continuous-wave external cavity laser, a detector system for measuring an absorption of laser light by the gas in the resonant optical cavity, wherein the ratio of the round-trip length of the external cavity laser to the round-trip length of the resonant optical cavity or its inverse value is between N?0.2 and N+0.2, where N is a positive integer number.

Abstract: The invention relates to a device comprising: a resonant tank (100) consisting of two primary tubes (105, 106) which are closed on the ends thereof and interconnected, close to each of the ends thereof, by two secondary tubes (109, 110), and provided with a gas-introducing means (118, 119); a first laser source (112) modulated to a first resonance frequency of the tank, which supplies an excitation energy in at least one of the primary tubes, with an emission wavelength corresponding to a local maximum absorption wavelength for a first gas, for generating a first stationary wave propagating along the secondary tubes; a second laser source (117) modulated to a second resonance frequency of the tank, which supplies an excitation energy in at least one of the secondary tubes, with an emission wavelength corresponding to a local maximum absorption wavelength for a second gas, for generating a second stationary wave propagating along the primary tubes; at least one acoustoelectric transducer (103, 104, 123, 124) a

Abstract: Disclosed is an apparatus for and method of measuring the concentration of F2 in the laser gas used in an excimer laser. Quartz Enhanced Photoacoustic Spectroscopy is used to obtain a direct measurement of F2 concentration quickly and using only a small sample volume.

Abstract: A downhole system includes a quartz enhanced photoacoustic spectrometer (QEPAS) configured to be positioned within a wellbore formed in a subterranean zone of a hydrocarbon formation, a sampling system coupled to the QEPAS, and a computer system connected to the QEPAS. The sampling system is configured to be positioned in the wellbore and obtain a sample of a wellbore fluid at a downhole location in the subterranean zone. The QEPAS is configured to spectroscopically scan the sample and to determine a plurality of quantities of a corresponding plurality of hydrocarbons in the same. The computer system includes one or more processors to perform operations including receiving the plurality of quantities of the plurality of hydrocarbons in the sample and determining a plurality of ratios, where each ratio is a ratio of one of the plurality of hydrocarbons with another of the plurality of hydrocarbons.

Abstract: 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.

Abstract: A method for measuring the concentration of a gas includes heating a first gas with a pulse of light, the pulse of light having a wavelength absorbed by the first gas, wherein the first gas exerts pressure on a flexible membrane. The method includes receiving a first signal indicating a first deflection of the membrane, wherein the first deflection is due to a change in pressure of the first gas and receiving a second signal indicating a second deflection of the membrane occurring after the first signal, wherein the second deflection is due to the change in pressure of the first gas. The method includes determining a difference between the first signal and the second signal and, based on the difference between the first signal and the second signal, determining a first concentration of the first gas.

Abstract: An acoustic wave detector may include: an exterior housing with an exterior housing wall, a gas chamber located within the exterior housing and configured to receive a gas therein. The exterior housing wall may include an aperture providing a gas passage between the gas chamber and the exterior of the acoustic wave detector. The acoustic wave detector may further include an excitation element configured to selectively excite gas molecules of a specific type in the gas received in the gas chamber in a time-varying fashion, thereby generating acoustic waves in the gas, and an acoustic wave sensor configured to detect the acoustic waves generated in the gas and acoustic waves generated outside of the acoustic wave detector. The acoustic wave sensor may have an acoustic port overlapping with the aperture in the exterior housing wall.

Abstract: An analyzer includes a quantum cascade laser that converts a cyclic driving signal to laser light; an optical receiver that receives the laser light having passed through a sample and outputs a detected signal depending on intensity of the laser light; and a data calculation portion that outputs information representing absorption characteristics of the sample. The data calculation portion includes a delaying unit that produces a time-delayed waveform by applying a time delay to a reference driving signal; an adding unit that produces a symmetrical waveform by adding the time-delayed waveform and the detected signal; a time inversion unit that produces a time-inverted waveform by time-inverting the symmetrical waveform; and a subtracting unit that produces a waveform difference between the time-inverted waveform and the symmetrical waveform. The data calculation portion repeatedly calculates the waveform difference by changing the time delay until the waveform difference is minimized.

Abstract: An acoustic wave detector may include: an exterior housing with an exterior housing wall, a gas chamber located within the exterior housing and configured to receive a gas therein. The exterior housing wall may include an aperture providing a gas passage between the gas chamber and the exterior of the acoustic wave detector. The acoustic wave detector may further include an excitation element configured to selectively excite gas molecules of a specific type in the gas received in the gas chamber in a time-varying fashion, thereby generating acoustic waves in the gas, and an acoustic wave sensor configured to detect the acoustic waves generated in the gas and acoustic waves generated outside of the acoustic wave detector. The acoustic wave sensor may have an acoustic port overlapping with the aperture in the exterior housing wall.

Abstract: 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.

Abstract: This invention employs an object information acquiring apparatus including a probe for receiving, as a received signal, an acoustic wave which is generated within an object irradiated with light and propagates on an object surface, and a processor for generating object information, which is information based on an internal optical characteristic value of the object, by using intensity of the received signal. The processor corrects the intensity of the received signal by using the reflectance upon the acoustic wave entering the probe which is calculated based on the angle of the acoustic wave entering the probe, and on the acoustic impedance and acoustic velocity of the object and the probe.

Abstract: A scanning probe microscope to measure a sample set on a sample mount in liquid includes a scanning mechanism to scan a cantilever provided with a probe at a free end along an X-axis, a Y-axis, and a Z-axis perpendicular to each other, and a liquid contact member including an optical transmission portion to transmit detection light for detecting a displacement of the cantilever, and arranged at least partially in contact with the liquid. The liquid contact member is not scanned by the scanning mechanism.

Abstract: A gas measurement device for measuring the concentration of a plurality of gas components by means of absorption measurement comprising a light source for infrared radiation (3) or a thermal radiator (4) as a light source (5), an optics (22) for bundling the light of the light source (5), a band pass filter (4) and a photoacoustic measurement cell (12) for measuring a plurality of gas concentrations, wherein a Fabry-Perot filter (6) is provided in front of the photoacoustic measurement cell (12) in addition to the band pass filter (4) for selecting the absorption spectra.

Abstract: A system for collecting gas samples emitted from skin and detecting concentrations of specified components therein. The system includes a collection chamber housing defining an interior space, the collection chamber housing having a gas inlet, a gas outlet, and an opening. The opening is configured for enclosing a skin portion from which to receive an emitted gas sample and sealing the interior space against the skin portion. An inert gas source is connected to the gas inlet, which is capable of allowing inert gas from the inert gas source to flow into the interior space. A gas cell is connected to the gas outlet, which is capable of allowing the inert gas and the gas sample to flow from the interior space into the gas cell. As a laser travels through the gas cell, power and optoacoustic signals are measured and used to determine a concentration of the specified component.

Abstract: A detector for detecting constituents of a liquid for use in liquid chromatography is disclosed. The detector includes a first optical flow cell body and a second optical flow cell body, each having a channel therethrough that allows passage of a liquid from an inlet port to an outlet port. The first and second optical flow cell bodies are arranged in series such that the liquid exiting the outlet port of the first optical flow cell body enters the inlet port of the second optical flow cell body. An insulator resides between the first optical flow cell body and the second optical flow cell body, which is adapted to electrically insulate the first optical flow cell body from the second optical flow cell body while allowing the liquid to pass from the first optical flow cell body to the second optical flow cell body.

Abstract: This invention relates to a method that makes the measurement of a trace gas concentration invariant or at least less affected to pressure variations in the gas and atmospheric pressure changes. This method neither requires a pressure sensor nor a pressure calibration routine. Furthermore, the method can be applied to other gas species present in the background gas or to the background gas itself that cross-interfere with the target gas of interest. This allows removing any pressure dependency of cross-interference parameters of other gas species and/or the background gas. The new method for accurately measuring a gas concentration is based on optimizing the wavelength modulation amplitude of the laser to minimum pressure dependency.

Abstract: A method and system for detecting composition of a physical space comprising: a laser beam source; an acoustic sensor; a beam focusing mechanism for focusing the laser beam at predetermined points in the physical space to generate a thermal inhomogeneity which results in the propagation of a pressure wave that propagates outward from the predetermined excitation point at a propagation velocity approximating the speed of sound for the particular composition of the media; at least one processor for controlling the timing for the laser beam focusing to generate thermal inhomogeneities; whereby the laser focal point is moved sequentially along the light-of-sight at various excitation points by the beam focusing mechanism approximately at the phase front velocity to define a series of predetermined excitation points and pressure wave propagations such that the series of pressure wave propagations combine to produce a coherent pressure wave detectable by the acoustic sensor.

Abstract: A photoacoustic gas sensor device for analyzing gas includes an emitter module and a pressure-sensitive module. The emitter module is arranged on a carrier substrate and emits light pulses. The pressure-sensitive module is arranged on the carrier substrate within a reference gas volume. The reference gas volume is separated from a volume intended to be filled with a gas to be analyzed. Further, the pressure-sensitive module generates a sensor signal indicating information on an acoustic wave caused by light pulses emitted by the emitter module interacting with a reference gas within the reference gas volume. Additionally, the emitter module is arranged so that light pulses emitted by the emitter module reach the reference gas volume after crossing the volume intended to be filled with the gas to be analyzed.

Abstract: A kit for detecting the presence of an explosive includes a pulsed focused energy source located at a target distance away from a substrate, the energy having a magnitude sufficient to release the internal energy of an explosive if present on the substrate and thereby generate an acoustic wave. The kit also includes a detector adapted to detect the acoustic wave at a detection distance away from the substrate.

Abstract: A device for generating a frequency reference including a frequency reference generation unit coupled to an integration cell to generate a frequency reference signal based on radio frequency (RF) produced pressure waves detected by an acoustic detector in the integration cell.

Abstract: The invention relates to a gas sensor having a mechanical microresonator, which has an excitation apparatus for optically exciting a mechanical oscillation of the microresonator as well as a reading apparatus for detecting the oscillation of the microresonator, wherein the reading apparatus comprises a waveguide which is implemented together with the microresonator on a dielectric or semiconducting substrate and is intended to optically read the oscillation of the microresonator, and wherein the excitation apparatus has an optical waveguide which is implemented on the same substrate and optically connects an excitation light source to the immediate surroundings of the microresonator. The invention also relates to a use of such a sensor to analyse a gas composition.

Abstract: A photoacoustic sensor, containing a resonance body, which at least partially delimits a space for receiving molecules to be detected, and a device for detecting an oscillation of the resonance body, including a device for optically detecting the location of at least one partial surface of the resonance body. A method for the photoacoustic detection of molecules in the gas phase and to a method for producing an optically integrated photoacoustic sensor.

Abstract: A gas measurement device for measuring the concentration of a plurality of gas components by means of absorption measurement comprising a light source for infrared radiation (3) or a thermal radiator (4) as a light source (5), an optics (22) for bundling the light of the light source (5), a band pass filter (4) and a photoacoustic measurement cell (12) for measuring a plurality of gas concentrations, wherein a Fabry-Perot filter (6) is provided in front of the photoacoustic measurement cell (12) in addition to the band pass filter (4) for selecting the absorption spectra

Abstract: Device for detecting a gas having an excitation device for exciting the gas by an electromagnetic wave having a wavelength corresponding approximately to that of the gas; and a detection device for detecting the excitation of the gas, the detection device having a waveguide connected to the excitation device, a part of which forms a movable element designed to be in contact with the gas and capable of being set into vibration by the impact of the excited gas molecules; and a measurement sensor, for measuring the vibration of the element, the measurement sensor and the element forming the detection device.

Abstract: An apparatus for measuring concentrations of airborne particulate matter may include, in one embodiment, a primary channel to receive air samples from the external environment. The air samples include particles of varying sizes. A microfluidic circuit communicates with the primary channel and small particles (having a size less than a threshold size) are diverted around a bend into a secondary channel. Remaining larger particles are unable to make the bend and continue through the primary channel. A mass-sensitive element communicating with the secondary channel includes a collection surface to collect the small particles. A resonant frequency of the mass-sensitive element is reduced in proportion to the mass of the particles collected.

Abstract: A single gas detector combines a dual cavity photo-acoustic gas sensor with a common microphone and common source. Electrical outputs from the microphone can be analyzed to determine an analyte gas concentration in the local region being monitored. Radiant energy from the common source can be directed into both cavities simultaneously. Alternately, the sensor can be used with two microphones to establish a concentration of each of two different gasses, or a gas and water vapor.

Abstract: A photoacoustic detector includes a sensing region for receiving atmospheric samples. One microphone receives acoustic samples from the sensing region. Another microphone receives acoustic samples from a displaced region. Microphone outputs can be subtracted to eliminate common noise and to generate an indicium of gas present in the sensing region.

Abstract: A method and system for detecting composition of a physical space comprising: a laser beam source; an acoustic sensor; a beam focusing mechanism for focusing the laser beam at predetermined points in the physical space to generate a thermal inhomogeneity which results in the propagation of a pressure wave that propagates outward from the predetermined excitation point at a propagation velocity approximating the speed of sound for the particular composition of the media; at least one processor for controlling the timing for the laser beam focusing to generate thermal inhomogeneities; whereby the laser focal point is moved sequentially along the light-of-sight at various excitation points by the beam focusing mechanism approximately at the phase front velocity to define a series of predetermined excitation points and pressure wave propagations such that the series of pressure wave propagations combine to produce a coherent pressure wave detectable by the acoustic sensor.