An emitter for emitting radiations at a specific wavelength includes a Joule-heated emitting electrical conductor to emit radiations at an emission temperature, a controller to control a variable voltage subjected to the Joule-heated emitting electrical conductor and modulated according to a duty cycle, the duty cycle being variable between a high-average power duty cycle during hot periods, so that the Joule-heated emitting electrical conductor is subjected to a high-average power to reach and maintain the emission temperature; and a low-average power duty cycle during cold periods alternated to the hot periods, so that the Joule-heated emitting electrical conductor is subjected to a low-average power to reach a temperature smaller than the emission temperature, wherein the high-average power duty cycle and the low-average power duty cycle is defined based on a temperature-indicative measured value indicative of the ambient temperature as measured.

A system for measuring gas concentration includes a package having a cavity and a port, a photoacoustic gas sensor device within the package, and a Micro Electro Mechanical System (“MEMS”) valve separate from the photoacoustic gas sensor device placed over the port of the package and to allow ambient gas diffusion into the cavity in a first mode of operation, and to prevent ambient gas diffusion into the cavity and to acoustically isolate the cavity in a second mode of operation.

A photo-acoustic gas sensor using a method for modulating the wavelength of the laser radiation, the modulation being obtained via judicious use of an electric current, called the generation current, which pumps the one or more laser sources, and is configured to cause the one or more laser sources to operate in pulsed mode, and of a current, called the base current, which takes non-zero values between each laser pulse with a lower magnitude than the magnitude of the generation current, the magnitude of base current being modulated so that the one or more laser sources emit, into the cell, light radiation having a wavelength that varies periodically about a central wavelength so as to take, at regular intervals, a value specifically suitable for the excitation of a gas to be detected, whereby an interaction between the light radiation and the gas to be detected contained in the cell induces the generation of acoustic waves at a resonant frequency of the cell.

An assembly (1) for measuring a relative humidity level inside a watch (2), the watch (2) provided with a movement (10) and a device (4) for determining the humidity level present in the enclosure (9) of a case (3) of this watch (2). The determination device (4) includes a receiver module (6a, 6b, 6c) for receiving at least one acoustic signal from a timepiece component (11) of said movement (10), and a control unit (7) connected to said receiver module (6a, 6b, 6c). The control unit (7) is configured to run a model for evaluating a water vapour content of a gaseous fluid contained inside the enclosure (9) based on the at least one acoustic signal received by the receiver module (6a, 6b, 6c).

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.

In an embodiment an electro-thermal device includes a heater, a readout circuit, a digital controller having a first input coupled to a first output of the readout circuit and a digital sigma-delta modulator having a first input coupled to an output of the digital controller and an output coupled to the heater.

An integrated photoacoustic transducer, sensing system and method for assisting in sensing a concentration of a species in a fluid such that the integrated photoacoustic transducer includes a waveguide structure. The waveguide structure has an optical resonance spectrally overlapping a spectral absorption line or band of the species. The photoacoustic transducer includes at least one acoustic cavity formed in a portion of the waveguide structure and configured for receiving the fluid for sensing comprising the species. The at least one acoustic cavity has an acoustic resonance spectrally overlapping with a harmonic of a modulation frequency. At least one acoustic transducer comprising a deformable mechanical portion is included in the photoacoustic transducer. The deformable mechanical portion is in direct acoustic communication with the at least one acoustic cavity and has an adjustable mechanical resonance, which can be brought into spectral overlap with an acoustic resonance of the least one acoustic cavity.

In accordance with an embodiment, a method of measuring a gas concentration includes modulating an infrared light source according to a frequency-hopped sequence or according to a pulse sequence, receiving a microphone signal from an output of a microphone acoustically coupled to a gas exposed to infrared light produced by the infrared light source; bandpass filtering the microphone signal using a bandpass filter; and estimating the gas concentration from the filtered microphone signal.

A photoacoustic sensor (100) is capable of detecting a predefined target gas in an area (Um). A process is capable of detecting the target gas with the use of such a sensor (100). A sample chamber (3) holds a gas sample (Gp) to be tested. Electromagnetic waves (eW) from a radiation source (1) pass through the sample chamber (3) and the detection chamber (4). The waves elicit in the detection chamber (4) an acoustic effect, which is measured by an acoustic sensor (7). The acoustic effect is correlated with the concentration of the target gas in the sample chamber (3). The detection chamber (4) is fluid-tightly sealed, is free from target gas and is filled with a replacement gas (Eg). The transmission of the replacement gas (Eg) has a spectral response similar to that of the transmission of the target gas in a predefined target gas wavelength range.

Aspects of the present disclosure are directed to a measuring device for determining a measured variable of a measuring gas by means of a photoacoustic method. In some embodiments, the measuring device includes a flow channel for the measuring gas having at least one feed line, a photoacoustic measuring cell and a discharge line. in such an embodiment, the measuring device further includes at least one acoustic filter member tuned to a useful frequency of the measuring cell, and at least one cavity resonator arranged on the flow channel.