There is provided an apparatus for measuring levels of a specified gas in exhaled breath, the apparatus comprising a photoacoustic sensor for providing a measurement representative of the level of the specified gas in the exhaled air, wherein the photoacoustic sensor comprises a light source that is modulated at a first frequency; a sound speed measurement module for measuring the sound speed of the exhaled breath, wherein the sound speed measurement module operates either at a second frequency that is substantially different to the first frequency or in a pulsed mode; wherein the first frequency of the modulated light source is adjusted during exhalation in accordance with the measured speed of sound of the exhaled breath.

There is provided an apparatus for measuring levels of a specified gas in exhaled breath, the apparatus comprising a photoacoustic sensor for providing a measurement representative of the level of the specified gas in the exhaled air, wherein the photoacoustic sensor comprises a light source that is modulated at a first frequency; a sound speed measurement module for measuring the sound speed of the exhaled breath, wherein the sound speed measurement module operates either at a second frequency that is substantially different to the first frequency or in a pulsed mode; wherein the first frequency of the modulated light source is adjusted during exhalation in accordance with the measured speed of sound of the exhaled breath.

A measuring apparatus for measuring a property of a medium includes: a density instrument for measuring a density of the medium; a speed of sound instrument for measuring a speed of sound in the medium; a temperature device for measuring a temperature of the medium; and an electronic circuit, wherein the foregoing components are arranged in a housing wherein the speed of sound instrument includes a pressure measuring cell, wherein the electronic circuit is configured to determine a compressibility from pressure measurements for at least two different pressure measuring cell volumes and to determine a speed of sound in the medium from the compressibility, wherein side surfaces of the pressure measuring cell each have a surface area of at most 0.5 square centimeter, and wherein the pressure measuring cell has a maximum volume of less than 5 cubic centimeters.

In some embodiments, apparatus and systems, as well as method and articles, may operate to launch acoustic waves along a first acoustic path length from an acoustic transducer toward an axis of rotation, to impinge on a first front surface of a target substantially fixed with respect to the axis, and to receive a reflection of the acoustic waves from the first front surface at the acoustic transducer. After rotating the acoustic transducer about the axis along a substantially circular path, additional activities may include launching acoustic waves along a second acoustic path length, different from the first acoustic path length, from the acoustic transducer toward the axis to impinge on a second front surface of the target, and receiving a reflection of the acoustic waves from the second front surface at the acoustic transducer. Additional apparatus, systems, and methods are disclosed.

In some embodiments, apparatus and systems, as well as method and articles, may operate to launch acoustic waves along a first acoustic path length from an acoustic transducer toward an axis of rotation, to impinge on a first front surface of a target substantially fixed with respect to the axis, and to receive a reflection of the acoustic waves from the first front surface at the acoustic transducer. After rotating the acoustic transducer about the axis along a substantially circular path, additional activities may include launching acoustic waves along a second acoustic path length, different from the first acoustic path length, from the acoustic transducer toward the axis to impinge on a second front surface of the target, and receiving a reflection of the acoustic waves from the second front surface at the acoustic transducer. Additional apparatus, systems, and methods are disclosed.

A fastener strain measurement system employs a probe incorporating a laser emitter to provide a laser beam and an acoustic detection device. A system controller is configured to detect an acoustic wave resulting from the ablation created by the laser beam and calculate fastener strain based on the detected acoustic wave.

An ultrasonic sensor assembly for testing a pipe includes a first and second transducer rings attached to the pipe and spaced apart along a length of the pipe. The first transducer ring includes a plurality of transmitters for transmitting a wave, such as a non-dispersive guided wave. The first transducer ring transmits the wave along the pipe. The second transducer ring includes a plurality of receivers for receiving the wave. A relative position of the first transducer ring with respect to a circumferential position of the second transducer ring is determined based on characteristics of the wave received by the second transducer ring. A method of positioning the ultrasonic sensor assembly on the pipe is also provided.

A sign detection device includes: a plurality of sensors disposed at a plurality of positions on a detection target object and configured to measure physical quantities at each position; a data acquisition unit for acquiring time-series fluctuation data of the physical quantities from the plurality of sensors; a calculation unit for calculating, from the time-series fluctuation data, a parameter indicating a correlation between the physical quantities at arbitrary two positions among the plurality of positions; and a detection unit for detecting a sign of sudden change in vibration of the detection object based on the parameter.

A sign detection device includes: a plurality of sensors disposed at a plurality of positions on a detection target object and configured to measure physical quantities at each position; a data acquisition unit for acquiring time-series fluctuation data of the physical quantities from the plurality of sensors; a calculation unit for calculating, from the time-series fluctuation data, a parameter indicating a correlation between the physical quantities at arbitrary two positions among the plurality of positions; and a detection unit for detecting a sign of sudden change in vibration of the detection object based on the parameter.

Ultrasonic pulse velocity is a parameter for assessing strength of concrete structures and studying elastic properties. A method involves transmission of longitudinal ultrasound by a transmitting transducer and receiving by a similar transducer. A transit time-measurement and associated triggering pulses provide the overall time-measurement resolution of at least 1 s. An ultrasonic pulse velocity measuring device capable of generating ultrasound in the solid materials supporting the propagation of ultrasound and precisely measuring the ultrasonic propagation delay time or the transit time is also disclosed. An ultrasonic transit time measurement device having provision for automatic pulse threshold error correction is also disclosed. A method to realize fast counting for generation of high resolution with relatively slower microcontrollers is also disclosed. Accuracy in the transit time measurement is improved by subtracting the threshold corrected zero offset (without material under test) from the threshold corrected transit time (with sample).