Fraunhofer-gesellschaft Zur Foerderung Der Angewandten Forschung E.v.

Andras Miklos

Judit Angster

Andreas Schmohl

A photoacoustic multipass cell includes a light source, an acoustic resonator and a reflecting arrangement configured in a concentrating manner for reflecting light into the acoustic resonator. Additionally, the light source is arranged at least partially within the reflecting arrangement.

Photoacoustic multipass cell with concentrating reflection means

A photoacoustic detection device includes a cylindrical acoustic resonator having an arrangement for guiding light essentially perpendicular to a cylinder axis in such a manner that a second azimuthal resonance of cylinder oscillation is excitable by absorption of the light.

Cylindrical photoacoustic detector with excitation of the second azimuthal resonance

A photoacoustic detector for providing a measurement, includes a first light source and a second light source each configured to provide light of a same intensity while retaining a same spectral distribution. Additionally, the photoacoustic detector includes a first beam path allocated to the first light source and at least one second beam path allocated to the second light source, wherein a different absorption of light occurs in the first path and the second beam path in at least one selected wavelength range. Further, the photoacoustic detector includes a photoacoustic measuring cell; and a mechanism for alternately guiding light from the first beam path and from the second beam path into the photoacoustic measuring cell. When alternately guiding light from the first beam path and from the second beam path into the photoacoustic measuring cell, the same intensity of the first light source and the second light source prevents generation of a photoacoustic signal due to light source intensity variation that distorts the measurement.

Photoacoustic detector with two beam paths for excitation light

A gas detector with a selectively adsorbing surface () and an acoustic measuring cell () is presented. The detector is characterized in that the selectively adsorbing surface () and the acoustic measuring cell () can be arranged with respect to one another such that gases desorbed by means of thermal desorption from the adsorbing surface () reach the acoustic measuring cell () and there trigger a pressure wave that can be measured by one or more acoustic pick-ups (), in particular microphones, which are arranged in the acoustic measuring cell (). Furthermore, a corresponding method is provided. The detector is particularly suitable for measuring contaminants in interior spaces and ventilation systems.

Gas detector having an acoustic measuring cell and selectively adsorbing surface

A method for measuring a photoacoustic signal using light sources that emit light at different wavelengths, wherein the method comprises electing a scanning frequency with which signals are recorded, determining a modulation frequency for each light source by dividing the scanning frequency by an integer division value that is different for each light source, exciting a photoacoustic signal in a photoacoustic measuring cell using the light sources and the modulation frequency, measuring, with a sound pressure sensor, a produced sound pressure, digitizing a signal of the sound pressure sensor, determining a signal component assignable to a respective light source by evaluating a sequence of digitized measured values, and filtering out measured value components that occur periodically with a period of a respective modulation frequency.

Method and device for measuring a photoacoustic signal with computer-assisted evaluation

A photoacoustic detector for measuring a concentration of fine dust particles in gas. The detector includes at least one acoustic sensor for detecting an acoustic signal. Additionally, the detector includes a pulsed light source for providing excitation light having a configurable pulse length and a configurable pulse repetition rate, wherein by changing the pulse length and/or the pulse repetition rate, a size distribution of the fine dust particles can be determined.

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Stuttgart, Germany

Andras Miklos