A combined vapor and/or gas concentration sensor and switch includes a resonating structure, a first alternating current, AC, voltage source coupled to a drive electrode, the first AC voltage source providing the resonating structure with a first voltage having an amplitude causing a first vibration mode of the resonating structure to exhibit a pull-in band and having a first frequency response adjacent to the pull-in band, where the first frequency response is nonlinear, a second AC voltage source coupled to the drive electrode and providing a second voltage having a frequency so that a second frequency response of the resonant structure, adjacent to a third vibration mode, is linear, and a read-out circuit coupled configured to determine a vapor and/or gas concentration based on a difference between (1) the frequency of the second voltage and (2) a frequency obtained by the read-out circuit from the resonating structure.

A photoacoustic sensor includes a first MEMS device and a second MEMS device. The first MEMS device includes a first MEMS component including an optical emitter, and a first optically transparent cover wafer-bonded to the first MEMS component, wherein the first MEMS component and the first optically transparent cover form a first closed cavity. The second MEMS device includes a second MEMS component including a pressure detector, and a second optically transparent cover wafer-bonded to the second MEMS component, wherein the second MEMS component and the second optically transparent cover form a second closed cavity.

A method is disclosed. In one example, the method includes bonding a first panel of a first material to a base panel in a first gas atmosphere, wherein multiple hermetically sealed first cavities encapsulating gas of the first gas atmosphere are formed between the first panel and the base panel. The method further includes bonding a second panel of a second material to at least one of the base panel and the first panel, wherein multiple second cavities are formed between the second panel and the at least one of the base panel and the first panel.

A measurement apparatus comprises a memory that stores instructions. The measurement apparatus comprises a processor that executes the instructions stored in the memory to: identify a propagation distance which is a length of a propagation path that a sound wave transmitted from a transmitting apparatus takes before reaching a receiving apparatus; determine, based on the identified propagation distance, a method to be used to identify a propagation time for the sound wave transmitted from the transmitting apparatus to reach the receiving apparatus from among a plurality of methods for identifying a propagation time of a sound wave; identify the propagation time for the sound wave transmitted from the transmitting apparatus to reach the receiving apparatus by the determined method; and measure an air characteristic of a location on the propagation path based on the identified propagation time and the identified propagation distance.

A sensor system for detecting water or air in a hollow member comprises a first acoustic sensor assembly in a first housing on one side of the hollow member, a second acoustic sensor assembly in a second housing on the opposite side, a controller unit connected to the first and/or second sensor assemblies, and where the first and second sensor assemblies and the controller unit are provided with power supply. Each of the first and second sensor assemblies comprises a set of probes connected to electronics for transmitting and receiving signals, and where the housings comprise fastening means for connecting the housings and the probes to the hollow member. The controller unit comprises a microcontroller, software for controlling and coordinating transmission and reception of signals between said probes, and means for registering and logging data generated by the sensor assemblies. A method detects water or air in a hollow member.

A gas analyzer uses continuous sonic signals through a conduit to determine the composition of a gas in the conduit. A transmitting transducer drives sonic signals at a fixed frequency and a second transducer receives the sonic signals. The phase shift between two signals corresponds to the speed of sound through the gas and is related to the composition of the gas. The electronic versions of these signals are processed by lowering, or dividing, the fixed frequency which expands the range of phase shift measurement and allows the determination of an expanded range for the gas composition. In an ozone generation system, the gas analyzer is highly suitable for determining the composition of gases derived from air as a gas of known composition and a calibration point.

A fluid sensor includes a housing structure forming a cavity for an IR emitter for emitting an IR radiation in the cavity, wherein the IR radiation has a center wavelength for providing an interaction of the IR radiation with the target fluid resulting in a temperature change in the cavity or in the housing structure, which effects a mechanical pulse in the housing structure, and an inertial detection sensor mechanically coupled to the housing structure for sensing the mechanical pulse in the housing structure.

A gas sensor having a heater, a receiver, and a space arranged between the heater and the receiver, is described, the heater being configured to generate a thermoacoustic sound wave propagating through the space by using a stimulation signal. The receiver is in this case configured to receive the thermoacoustic sound wave that has propagated through the space and to convert it into a reception signal that has a time-of-flight-dependent shift with respect to the stimulation signal and therefore information relating to the gas concentration in the space.

A photoacoustic sensor includes a first MEMS device and a second MEMS device. The first MEMS device includes a first MEMS component including an optical emitter, and a first optically transparent cover wafer-bonded to the first MEMS component, wherein the first MEMS component and the first optically transparent cover form a first closed cavity. The second MEMS device includes a second MEMS component including a pressure detector, and a second optically transparent cover wafer-bonded to the second MEMS component, wherein the second MEMS component and the second optically transparent cover form a second closed cavity.

An apparatus for in-situ calibration of a photoacoustic sensor includes a measurement device configured to measure an electric signal at an IR emitter of the photoacoustic sensor, wherein the IR emitter generates an electromagnetic spectrum based on the electric signal; and a calibration unit including processing circuitry, configured to compare the electric signal with a comparison value to generate a comparison result used as calibration information. When performing the in-situ calibration, the calibration unit is configured to adjust the electric signal based on the calibration information, or the calibration unit is configured to process an output signal of the photoacoustic sensor based on the calibration information to obtain an adjusted output signal of the photoacoustic sensor.