An environmental condition may be measured with a sensor (10) including a wire (20) having an ultrasonic signal transmission characteristic that varies in response to the environmental condition by sensing ultrasonic energy propagated through the wire using multiple types of propagation, and separating an effect of temperature on the wire from an effect of strain on the wire using the sensed ultrasonic energy propagated through the wire using the multiple types of propagation. A positive feedback loop may be used to excite the wire such that strain in the wire is based upon a sensed resonant frequency, while a square wave with a controlled duty cycle may be used to excite the wire at multiple excitation frequencies. A phase matched cone (200, 210) may be used to couple ultrasonic energy between a waveguide wire (202, 212) and a transducer (204, 214).

A method includes computing one or more values of at least one parameter at respective times during an exhalation of a subject, based on one or more properties of sound passing through air exhaled by the subject during the exhalation, the parameter being related to a concentration of a gas in the air. The method further includes generating an output in response to the values. Other embodiments are also described.

A method and system of responding to adverse environmental conditions local to a user of an oxygen concentrator is disclosed. Physiological data of the user is collected. Operational data of the oxygen concentrator is collected during operation of the oxygen concentrator. Environment data local to the oxygen concentrator is collected. Based on the collected environmental data, it is determined whether adverse environmental conditions exist local to the oxygen concentrator. The collected physiological, operational, and environmental data are analyzed to determine a responsive action to the determined adverse environmental conditions. The responsive action is communicated to the user.

A collimated beam (23) of a surface acoustic wave propagates on a piezoelectric substrate (22) while passing through sensitive film (25) to adsorb a sensing gas. Signal processing unit (40) transmits an exciting burst signal to sensor electrode (24) to excite the collimated beam (23), receives first and second returned burst signals after the collimated beam (23) has propagated, and calculates a target gas parameter by a target leakage factor of the background gas and a relation between reference gas parameters and reference leakage factors of reference gases, the leakage factor is provided by first and second attenuations of the first and second returned burst signals, respectively, using waveform data of the first and second returned burst signals.

Multifunctional RF limiting amplifiers having various configurations and functions are disclosed. In a first configuration, the RF limiting amplifier includes an active load output circuit that allows one to adjust the output impedance based upon the anticipated connected load impedance. In a second configuration, the RF limiting amplifier includes a pair of emitter-followers to buffer the output of a first stage, allowing the RF limiting amplifier to drive one or more second stages. A third configuration includes a pair of RF limiting amplifiers with their outputs mixed to implement a down conversion function. The third configuration may be used to drive dual SAW resonators for detecting the presence of biological or chemical agents. The RF limiting amplifier may be implemented in either bipolar junction transistors or CMOS transistors.

A polymer material is contained in a sensing film of a sensor element having a quartz plate, an electrode made of a metal film provided on the quartz plate, and a sensing film provided on the electrode, and has a structural unit that contains one or more ethylene unsaturated bonds and is originated from a compound containing one or more functional groups reactive to a gas.

Surface modifications and improvements to piezoelectric-based sensors, such as QCMs and other piezoelectric devices, that significantly increase the sensitivity and the specificity (selectivity). These modifications can comprise mechanical and chemical changes to the surfaces of the sensors, either individually or together. For example, nanosize structures may be provided on the surface to improve sensitivity. Additionally, chemical coatings may be tethered to the surfaces, walls, or crystal to provide targeted sensitivity. Additionally, porous, layered and multiple sensor arrays may be formed to enhance sensitivity and selectivity.

Embodiments provide an odor identification system including an operation array unit including at least two or more sensors which interact with odor causative substances included in an odor factor of a gas sample, a sensor data processing unit processing data obtained by interaction with the odor factor in the operation array unit, an odor factor information storing unit storing information of the odor factor and the interaction pattern information of the odor factor in advance, and a pattern identification unit identifying the odor factor on the basis of an interaction pattern while referring to the pattern processed by the sensor data processing unit and the information of the odor factor information storing unit, and collating the interaction pattern with the known odor information, wherein the odor of the object to be measured is contained.

A fluid mixture parameter determination (FMPD) system for analyzing a fluid mixture while moving includes a computing system and at least one material model that includes two or more model parameters for a plurality of material compositions stored in the memory. An ultrasonic sensor and a millimeter wave (MMW) sensor are each coupled to sense the fluid mixture and are coupled to the computing system. The ultrasonic sensor is for providing ultrasonic data to the computing system including a velocity of the fluid mixture or a volumetric flow, and a velocity of sound (VoS) through the fluid mixture. The MMW sensor is for providing MMW velocity data to the computing system. The computing system is for utilizing the material model together with the ultrasonic data and the MMW velocity data for identifying parameters including a plurality of components in the fluid mixture and a concentration for the plurality of components.

A system for measuring a gas concentration, the system including: a first oscillator including a first surface for placement in a sampling location, wherein the first oscillator oscillates at a frequency greater than 20,000 Hz but less than 300,000,000 Hz; a first counter to accumulate a count of oscillations of the first oscillator; and a comparator to calculate a difference between the accumulated counts of the first oscillator and a reference, wherein the difference calculated by the comparator is sampled at a frequency of less than 100 Hz.