Abstract:
A method of indirectly measuring the diluent (nitrogen and carbon dioxide) concentrations in a natural gas mixture. The molecular weight of the gas is modeled as a function of the speed of sound in the gas, the diluent concentrations in the gas, and constant values, resulting in a model equation. A set of reference gas mixtures with known molecular weights and diluent concentrations is used to calculate the constant values. For the gas in question, if the speed of sound in the gas is measured at three states, the three resulting expressions of molecular weight can be solved for the nitrogen and carbon dioxide concentrations in the gas mixture.
Abstract:
A multiple mode sensing system is described, which can be configured from an acoustic wave sensor that includes a plurality of sensing components for monitoring a chemical species. The plurality of sensing components can be disposed within a cavity formed from a plurality of walls of said acoustic wave sensor, such that each sensing component is coated with a differing sensing film. The multiple modes sensing system also includes a plurality of oscillators associated with sensing components, wherein each sensing component is generally located in a feedback loop with identical oscillators to thereby provide a multiple modes acoustic wave sensor that provides multiple modes frequency outputs for the detection and desorption of a chemical species.
Abstract:
A device for analyzing the type of gas burned in a gas-fired apparatus, comprising a body provided with at least one opening for introducing gas and for the subsequent flow of gas into sound emission means, which are adapted to emit a frequency signal that is inversely proportional to the density of the gas, the signal being transduced and sent to a control unit that is adapted to identify the signal and match it to a type of gas.
Abstract:
Die Erfindung betrifft einen piezoakustischen Resonator (2) mit einer auf einem Substrat (3) angeordneten unteren schichtförmigen Elektrode (6), einer oberen schichtförmigen Elektrode (5) und einer zwischen den Elektroden (5, 6) angeordneten piezoelektrischen Schicht (4). Der Resonator (2) ist dadurch gekennzeichnet, dass die untere Elektrode (6) eine Schichtdicke aufweist, die aus dem Bereich von einem Zehntel bis neun Zehntel einer Wellenlänge (λ) der Schwingung des piezoakustischen Resonators (2) ausgewählt ist. Vorzugsweise entspricht die Schichtdicke der unteren Elektrode (6) im Wesentlichen einem Viertel (λ/4) oder drei Viertel (λ/4) der Wellenlänge der Schwingung des Resonators (2). Durch diese Massnahme resultiert ein Resonator mit sehr hoher Massensensitivität. Neben dem Resonator wird auch ein Verfahren zur Detektion mindestens einer Substanz eines Fluids unter Verwendung des piezoakustischen Resonators (2) angegeben.
Abstract:
Vorgeschlagen wird ein Verfahren zur Ultraschall-Laufzeit-Mengenmessung eines strömenden Fluids, bei dem die Laufzeit eines Ultraschall-Signals (70) entgegen und mit der Strömung (R) gemessen und daraus die Strömungsgeschwindigkeit des Fluids ermittelt wird. Bei dem vorgeschlagenen Verfahren werden zusätzlich die Reflexionen des Ultraschall-Signals (70) an Partikeln im Fluid erfasst, um daraus die Konzentration der Partikel zu ermitteln. Es wird außerdem eine Vorrichtung zur Durchführung eines solchen Verfahrens vorgeschlagen, die ausgestattet ist mit wenigstens zwei Ultraschall-Wandlern (32a, 32b, 34a, 34b, 36a, 36b, 38a, 38b), welche umschaltbar sind vom Sendezustand in einen Empfangszustand, wobei die Ultraschall-Wandler im Sendezustand Ultraschallsignale (70) aussenden können, die von Ultraschall-Wandlern im Empfangszustand empfangen werden können, nachdem sie den zu untersuchenden Fluidstrom (20) durchquert haben. Wenigstens einer der Ultraschall-Wandler (32a, 32b, 34a, 34b, 36a, 36b, 38a, 38b) der Vorrichtung ist so schnell von Senden auf Empfang umschaltbar, daß er die Reflexionen (E1, E2, E3) seines ausgesandten Signals (70) empfangen kann. Es können auch zusätzliche Ultraschall-Wandler (32c) vorgesehen sein, die so angeordnet sind, dass sie die Reflexionen (E1, E2, E3) des von den Ultraschall-Wandlern im Sendezustand ausgesandten Signales (70) empfangen können.
Abstract:
The invention concerns an acoustic sensor for determining the composition or concentration relations of a gas mixture within at least one measuring cell (1), including means for transport (6, 7) of said gas mixture to and from said measuring cell (1). The measuring cell is defined by at least two essentially planar and parallel plates (2, 3) at least one of which is conditioned to be subjected to mechanical vibrations by means of electrical activation. The thereby appearing interaction from acoustic waves within the gas mixture is electrically readable. Activation and readout is performed e g by electrostatic, piezoelectric, piezoresistive or electrothermal action. The readability concerns e g one in the frequency domain measurable extreme value, alternatively a phase or time difference, constituting a measure of the propagation velocity within the gas mixture, which is being the frequency controlling element of at least one oscillator circuit being built up from active and passive electronic components integrated into at least one silicon die (41). The wavelength of the acoustic waves is determined by at least one spacer (4) defining the distance between said plates (2, 3). Means (10, 11) for temperature measurement and electrical heating of said plates (2, 3) also prevail in a preferred embodiment, along with filter (51) for separation, adsorption or trapping of certain in said mixture included compounds. The geometric design of the measuring cell (1) and the plates (2, 3) is defined by a multistage process of selective or anisotropic pattern deposition and etching of single crystalline silicon or other semiconductor material.
Abstract:
A system for determining the composition of a multiple component fluid as gas or liquid and for determining linear flow comprising a pulse transmitter (10) and pulse receiver (20) used in at least one sing-around circuit that determines the velocity of an audio signal (12) in the multiple component fluid, which velocity is correlatable to a known data base for the multiple component fluid, and where the electronics of a trigger signal circuit (30), amplifier (32), pulser (60), rectifier (34), square wave converter, keep alive circuit (50), alternative pulse width adjuster (40) and gate circuit or digital filter (38) is arranged to determine a signal delay between pulse transmitting and receiving. A method for determining flow in a controlled dynamic fluid supply system uses two of such inventive circuits with independent transmitters and receivers disposed about the fluid of measurement interest, one pair of which transmitter and receiver is set at an angle non-perpendicular to the direction of fluid flow.
Abstract:
A device for detecting chemical substances includes a plurality of sensors arranged in an array. The sensors are connected to respective oscillator circuits which drive the sensors, and the oscillator circuits are coupled to a power multiplexer which provides the circuits with power according to a timing pattern such that not all of the oscillator circuits are activated at any one time. Preferably, only one oscillator circuit is activated at any given time. This multiplexing arrangement saves power and substantially eliminates cross talk between the oscillator circuits. The oscillator circuits are preferably application specific integrated circuits (ASICs), and the sensors are preferably surface acoustic wave (SAW) devices. In use, the SAW sensors are exposed to a gas, such as air, containing the chemical substance to be detected. Signals from the SAW sensors are analyzed to identify the chemical substance.
Abstract:
A leak detection device (300) securable in detection proximity to a fluid vessel (not shown). The leak detection device includes a sensor element (330) such as a piezoelectric crystal (332) placed within a housing upper portion (312) and a monitoring assembly (340) placed within a housing lower portion (314). The sensor element has a monitorable characteristic, and this monitorable characteristic changes in exposure to the fluid contained inside the fluid vessel. The monitoring assembly is responsive to the monitorable characteristic and produces a visual and audible alarm output (350, 352) in response to such change in the monitorable characteristic. The fluid vessel and leak detection device together may form an assembly (not shown) including a shroud or cover over the leak detection device and a leak-susceptible portion of the fluid vessel, to provide an isolated microenvironment in which the leak detection device is operated.
Abstract:
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 senor arrays may be formed to enhance sensitivity and selectivity.