Abstract: In order to be able to couple as great a fraction as possible of ultrasonic measuring signals into a medium to be measured, an ultrasonic sensor is provided with a cup-shape and includes a housing and an oscillatable unit for producing the ultrasonic signals. The oscillatable unit is composed of a plurality of components and is so embodied that it has a node plane, which is oriented essentially perpendicularly to the radiating or receiving direction of the ultrasonic measuring signals. At least a portion of the outer surface of the oscillatable unit is connected with the housing in the region of the node plane of the oscillatable unit.

Abstract: A transit-time flow sensor determines a rate at which fluid flows by measuring a propagation time difference between upstream and downstream acoustic transmissions. This may involve providing an acoustic path consisting of sequentially traversed path segments and a repeating arrangement that uses the energy in a received pulse to repeat the pulse in the next sequential segment.

Abstract: An ultrasonic measuring unit and a method for detecting ultrasonic signal run-times, in which the ultrasonic measuring unit has two ultrasonic transducers for coupling ultrasonic signals into a flowing medium. Analysis electronics are provided to be accommodated on or in a flow tube, in which a gaseous medium such as circulating air flows. A probe unit is accommodated in the flow tube, the probe unit being assigned a temperature probe having a flow around it, whose measured value is used for correcting a temperature signal detected by ultrasound.

Abstract: A flow meter filter system (200) according to an embodiment of the invention includes a noise pass filter (203) configured to receive a first version of a flow meter signal and filter out the flow meter data from the flow meter signal to leave a noise signal, a noise quantifier (204) configured to receive the noise signal from the noise pass filter (203) and measure noise characteristics of the noise signal, a damping adjuster (205) configured to receive the noise characteristics from the noise quantifier (204) and generate a damping value based on the noise characteristics, and a filter element (206) configured to receive a second version of the flow meter signal and receive the damping value from the damping adjuster (205), with the filter element (206) being further configured to damp the second version of the flow meter signal based on the damping value in order to produce a filtered flow meter signal.

Abstract: A transit-time flow sensor determines a rate at which fluid flows by measuring a propagation time difference between upstream and downstream acoustic transmissions. This may involve providing an acoustic path consisting of sequentially traversed path segments and a repeating arrangement that uses the energy in a received pulse to repeat the pulse in the next sequential segment.

Abstract: An ultrasonic flow sensor for measuring the volumetric flow rate of a flowing medium through a flow channel having a transducer array which is situated within the flow cross section of the flow channel and which generates ultrasonic waves which propagate in the flow cross section of the flow channel transversally to a flow direction of the flowing medium, the ultrasonic transducer array having an interlaid arrangement of transducer elements which act alternately as transmitting and receiving antennas, so that all emitted individual sound waves interfere to form common wave fronts.

Abstract: Flowmeter comprising at least two ultrasonic transducers that are mounted on a container which is penetrated by a medium in a certain direction of flow. The ultrasonic transducers alternately transmit and receive ultrasonic test signals in the direction of flow and counter to the direction of flow. The flowmeter further comprises a control/evaluation unit which determines and/or monitors the volume flow of the medium inside the container based on the difference in the travel time of the ultrasonic test signals propagating in the direction of flow and counter to the direction of flow. The ultrasonic transducers are configured such that they transmit and receive ultrasonic test signals or sound fields having a large aperture angle or a great beam expansion.

Abstract: Measuring volume flows or mass flows in the intake system of motor vehicle internal combustion engines plays an important role in reducing harmful emissions. Therefore, an ultrasonic flow meter for measuring a flow velocity of a fluid flowing in an essentially laminar flow in the main flow direction is described. The ultrasonic flow meter has at least two ultrasonic transducers, the ultrasonic transducers being able to emit and/or receive ultrasonic waves at an angle ? to the main flow direction which is different from 90°. Furthermore, the ultrasonic flow meter has at least one turbulator situated upstream from at least one ultrasonic transducer in the main flow direction of the fluid, which generates longitudinal eddies in at least one zone adjacent to the at least one ultrasonic transducer, in particular in a protrusion in a wall of a flow pipe and thus improves the flow of the fluid in this zone in the flow pipe.

Abstract: In an ultrasonic flow meter for measuring a flow rate of a fluid flowing through a conduit by detecting a propagating time difference between a forward propagating time of an ultrasonic wave propagating within the conduit in a forward direction and a backward propagating time of an ultrasonic wave propagating within the conduit in a backward direction, forward and backward ultrasonic wave signals generated by ultrasonic vibrating elements are sampled to derive forward and backward digital data series x and y, which are stored in a memory, the forward and backward digital data series x and y are read out of the first and second memory units and total sums of absolute difference values between the forward and backward digital data series x and y are calculated, while data positions of these backward and forward digital data series x and y are relatively shifted, a shift amount of data positions at which a total sum of absolute difference values becomes minimum is detected, an ultrasonic propagating time differe

Abstract: A flow meter filter system (200) according to an embodiment of the invention includes a noise pass filter (203) configured to receive a first version of a flow meter signal and filter out the flow meter data from the flow meter signal to leave a noise signal, a noise quantifier (204) configured to receive the noise signal from the noise pass filter (203) and measure noise characteristics of the noise signal, a damping adjuster (205) configured to receive the noise characteristics from the noise quantifier (204) and generate a damping value based on the noise characteristics, and a filter element (206) configured to receive a second version of the flow meter signal and receive the damping value from the damping adjuster (205), with the filter element (206) being further configured to damp the second version of the flow meter signal based on the damping value in order to produce a filtered flow meter signal.

Abstract: An ultrasonic signal processing method for improving the signal-to-noise ratio in ultrasonic measurements comprises the transmission of a predefined timed sequence of a number of ultrasonic burst signals at a first transducer, and reception of a signal representing said transmitted sequence of ultrasonic burst signals at a second transducer. This signal is processed by addition of multiple time-shifted copies of the received signal to said original received signal to obtain a sum of the original received signal and its time-shifted copies. An original burst signal having an improved signal-to-noise ratio is reconstructed from this sum.

Abstract: An apparatus for the positioning of a clamp-on flow measuring device on a containment, which has a medium flowing through it. The apparatus includes at least two ultrasonic transducers, which emit measuring signals into the containment and/or receive measuring signals from the containment, a positioning unit for the variable positioning of the ultrasonic transducers on the containment, a control/evaluation unit, which calculates from predetermined process and/or system variables a characteristic, desired variable of the measuring signals and which determines on the basis of a comparison of the calculated, desired variable with the corresponding, measured, actual variable, whether the ultrasonic transducers are optimally positioned or whether the position of the ultrasonic transducers need to be changed, and an indicating unit, which indicates to operating personnel a required change of position and/or the direction in which a change of position needs to be made.

Abstract: An ultrasonic gas flowmeter includes a measuring pipe with flowing gas, transmitting and receiving sound transducers, transmission and reception electronics, and evaluation electronics. The sound transducers (7, 8, 9, 10) are designed as capacitive electro-acoustic ultrasonic transducers to construct a flowmeter with improved capacity, especially in view of temperature stability and the reduction and consideration of a temperature profile. Devices (5, 6) are provided to level the gas temperature profile and to minimize the influence of the temperature profile on the flow measurement. A more accurate and dependable detection of the volume flow or the mass flow of gases is to be achieved, especially in highly dynamic flows, for the method of determining the flow of gases whereby the mean flow velocity is determined and the flowing gas quantity is determined with highly synchronized resolution from the two transit times of two acoustic signals.

Abstract: A sonic- or ultrasonic flowmeter, suitable for replacement of differential pressure flowmeters, comprising: a pipe segment, to be connected to a first and a second pipe, each having a diameter, which complies to an industry standard for pipe diameters used in differential pressure flow measurement, having a length (L), which is equal to a standard length for a flow restricting element of a differential pressure flowmeter, having a diameter (D), which is equal to a standard for pipe diameters used in differential pressure flow measurement, comprising a first standard connector located on a first end of the pipe segment, and a second standard connector located on a second end of the pipe segment, a primary flow sensor, comprising at least one sonic- or ultrasonic transducer for transmission and/or reception of sonic- or ultrasonic signals through the pipe segment, mounted on the pipe segment, and a sensor electronic for providing a measurement signal representing a flow of fluid through the pipe segment, based

Abstract: Techniques for fluid measurement include the ability to introduce a vibration to a container wall and to detect the vibration after the vibration has propagated at least partially around the container wall. Based on the detection of the vibration, the techniques also include the ability to determine a fluid state.

Abstract: A flow measurement system including at least first and second ultrasonic transducers coupled to an existing conduit, a damping material about the conduit between the first and second ultrasonic transducers to prevent crosstalk, a damping material about the conduit upstream of the first ultrasonic transducer to attenuate system background noise travelling in the conduit at large, and a damping material about the conduit downstream of the second ultrasonic transducer to attenuate system background noise travelling in the conduit at large.

Abstract: A transmitting and receiving circuit for an ultrasonic flowmeter. In such circuits, an ultrasonic transducer is typically used as both transmitter and receiver. This is obtained by using switching means, for example in the form of CMOS switches. However, problems arise with ringings of a transducer when having acted as a transmitter. This unwanted ringing makes the crystal of the transducer act as an additional signal generator, and the signal is coupled via parasitic capacitances in a switching means to the receiving ultrasonic transducer. This problem is solved by connecting one pole of a short circuit switch (S3, S4) to the ultrasonic transducer (TR1, TR2) or to the switching means (S1, S2) and the other pole of the short circuit switch to ground. Keeping the short circuit switch closed when the switching means is open, and open when the switching means is closed, creates a decoupling path for the unwanted signal, thereby improving the accuracy of the transmitting and receiving circuit.

Abstract: The present invention provides a small, low power consumption ultrasonic flow velocity meter. The burst signal generation section 110 generates two kinds of burst signals with a phase difference and sends these burst signals to a pair of transmission/reception ultrasonic transducers 6 and 7 located on the upstream side and downstream side of the conduit to be measured 9. Upon reception of the corresponding burst signals, the pair of the transmission/reception ultrasonic transducers 6 and 7 convert the burst signals, send ultrasonic waves with a phase difference to the conduit to be measured 9, receive the ultrasonic wave sent by the other transmission/reception ultrasonic transducer and propagated through the conduit to be measured and convert the ultrasonic waves to received signals.

Abstract: An ultrasonic flow-measuring method determines the flow rate of a medium flowing through a line is determined by measuring the runtime of an ultrasonic signal that travels from a first ultrasonic transducer to at least one other ultrasonic transducer. The runtime of the ultrasonic signal as it makes m passes in immediate succession through a predefined path over a predefined path length and at a predefined angle relative to the flow direction is measured, and the runtime of the ultrasonic signal as it makes n passes in immediate succession through the predefined path over the predefined path length at the predefined angle relative to the flow direction is measured, with m and n being mutually different integers, and the dead time of the ultrasonic flow-measuring process is determined on the basis of the measured runtimes. This ultrasonic flow-measuring method permits real-time compensation for the dead time during the actual measuring process, the result being highly accurate measurements.

Abstract: The invention concerns a method for measuring the displacement of a fluid in a conduit, by measuring the transit time of ultrasounds between two transducers (12, 13), in one direction and in the other, characterised in that it consists in: simultaneously exciting (16) both transducers; then simultaneously measuring (17, 18) the signals received on each of the transducers coming from the other transducer. The measured signals can then be digitised and correlated to determine the difference between the transit times. The invention enables to obtain faster and more reliable, measurement of transit times between transducers.

Abstract: A tag flow measurement system wherein a first and a second measurement path are provided across a flowing fluid, and a receiver in each path receives signals modulated by scatters in the fluid. The direction of signal propagation in one path faces in an opposite sense to, e.g., is anti-parallel to, the direction of propagation in the other path, and the two receiver outputs are correlated to determine a time interval representative of flow velocity. In one embodiment each path is defined by a transmitter on one side of the conduit and a receiver on the other side of the conduit, and the positions or orientations of transmitter and receiver are reversed in the second pair. Thus, the first transmitter may lie on the same side of the conduit as the second receiver, and the second transmitter may lie on the same side of the conduit as the first receiver. Diametral or chordal paths may be used.

Abstract: A flowmeter detector for determining the flow volume of a fluid medium that includes a measuring line having first and second ends and a fluid medium entry and exit ports adjacent the fist and second ends and fluid medium flowing between the entry and exit ports is disclosed. An acoustic transducer is located at each end of the measuring line and each acoustic transducer has an overall dimension less than the cross-section diameter of the measuring line. The acoustic transducers are first operated to simultaneously transmit pulsed acoustic energy into the measuring line. The transducers are subsequently operated to receive the acoustic energy propagated through the measuring line. The flow volume is determined by evaluating the difference in the travel times of the pulsed acoustic energy propagated through the measuring line.

Abstract: A flow rate measuring apparatus includes: flow rate detection section 2 and 3 provided in a fluid flow path 1; a measuring section 10 for measuring an output from the flow rate detection sections 2 and 3; a cycle setting section 9 for setting a measurement cycle of the flow rate detection sections 2 and 3; a resolution setting section 7 for setting a measurement resolution of the measuring section 10; a flow rate calculation section 11 for calculating a flow rate based on an output from the measuring section 10; and a measurement control section 12 for controlling each of the sections.

Abstract: The present invention provides a small, low power consumption ultrasonic flow velocity meter. The burst signal generation section 110 generates two kinds of burst signals with a phase difference and sends these burst signals to a pair of transmission/reception ultrasonic transducers 6 and 7 located on the upstream side and downstream side of the conduit to be measured 9. Upon reception of the corresponding burst signals, the pair of the transmission/reception ultrasonic transducers 6 and 7 convert the burst signals, send ultrasonic waves with a phase difference to the conduit to be measured 9, receive the ultrasonic wave sent by the other transmission/reception ultrasonic transducer and propagated through the conduit to be measured and convert the ultrasonic waves to received signals.

Abstract: Embodiments of the invention provide an algorithm for enhancing the transit time measurement of an ultrasonic wave through a fluid, and criteria for evaluating the suitability for various waveforms with regard to noise rejection. The transit time calculation provides a greater noise immunity and accuracy than techniques used in the prior art, and allows a measure of weighting of dispersed signals with different arrival times. The transit time calculation utilizes either the transmitted signal or the measurement of a reference system, the calculation of the squared convolution of this signal with the received signal, and the calculation of the transit time from the time-weighted squared convolution signal over a suitable interval defined by the minimums of the squared convolution signal. In the case of dispersion where the arrival times are symmetrically displaced around a mean transit time, or if asymmetric dispersion is suitably within the main lobe, the calculation properly weights the composite signal.

Abstract: A flow meter includes a flow path through which a fluid flows; a pair of transceivers for sending and receiving an ultrasonic wave propagating across the flow path; and a flow calculation section for calculating a flow rate of the fluid flowing through the flow path based on a result of the ultrasonic wave being sent and received by the pair of transceivers. The flow path has an equal flow speed area in which the fluid flows at a substantially equal flow speed over an entire flow rate area ranging from a high flow rate area to a low flow rate area. The pair of transceivers send and receive the ultrasonic wave so that the ultrasonic wave propagates in the equal flow speed area.

Abstract: A flowmeter detector for determining the flow volume of a fluid medium that includes a measuring line having first and second ends and a fluid medium entry and exit ports adjacent the fist and second ends and fluid medium flowing between the entry and exit ports is disclosed. An acoustic transducer is located at each end of the measuring line and each acoustic transducer has an overall dimension less than the cross-section diameter of the measuring line. The acoustic transducers are first operated to simultaneously transmit pulsed acoustic energy into the measuring line. The transducers are subsequently operated to receive the acoustic energy propagated through the measuring line. The flow volume is determined by evaluating the difference in the travel times of the pulsed acoustic energy propagated through the measuring line.

Abstract: An apparatus for noninvasively monitoring the flow and/or the composition of a flowing liquid using ultrasound is described. The position of the resonance peaks for a fluid excited by a swept-frequency ultrasonic signal have been found to change frequency both in response to a change in composition and in response to a change in the flow velocity thereof. Additionally, the distance between successive resonance peaks does not change as a function of flow, but rather in response to a change in composition. Thus, a measurement of both parameters (resonance position and resonance spacing), once calibrated, permits the simultaneous determination of flow rate and composition using the apparatus and method of the present invention.

Abstract: A system for determining the composition of a multiple-component fluid and for determining linear flow comprising at least one sing-around circuit that determines the velocity of a signal in the multiple-component fluid and that is correlatable to a database for the multiple-component fluid. A system for determining flow uses two of the inventive circuits, one of which is set at an angle that is not perpendicular to the direction of flow.

Abstract: A zero crossing detector has an analyzer which determines a zero level crossing of a currently input electrical pulse packet and which emits a trigger signal indicative of a determination having been made, and a pre-trigger unit which monitors variations in the amplitude of the current input pulse packet to detect a crossing of a pre-trigger level. The detector further includes a control unit operably connected to the pre-trigger unit which compares the amplitude of the pre-trigger level with any amplitude of a signal derived from the current or a previous input electrical pulse packet, and which automatically controls the amplitude of the pre-trigger level to maintain a working difference therebetween.

Abstract: In a method for determining the flow rate of a fluid flowing in a channel (2), the fluid being constituted by a liquid or a gas, two pulse shaped, oscillating signals are sent through the medium with one signal directed against (14) and the other signal directed with (12) the flow direction (4) of the fluid. The transmitted signals are received and the flow rate is determined by means of the phase shift between the received, pulse shaped signals caused by the flow of the fluid. The phase shift (20) between the signals is determined while compensating for the dwell time of the pulse shaped oscillating signals in the fluid.

Abstract: A clamp-on ultrasonic measurement system for a gas or other fluid typically of low acoustic impedance such as low pressure steam or flare gas. The system includes a first ultrasonic signal transducer which clamps to the conduit, and a second ultrasonic signal transducer clamped on the conduit across from the first transducer. Each transducer is operated to transmit to, and receive from, the other along contrapropagation signal paths. The transducers generate a shear wave signal that skips within the conduit wall to coherently energize a region of the wall and launch ultrasonic signal energy at a defined angle across the direction of flow. The receiver is symmetrically arranged and positioned to respond to signal energy received along the path through the fluid.

Abstract: An equipment specifying system of the present invention includes: a flow path for supplying gas to a plurality of pieces of equipment; an ultrasonic propagation signal measuring section for measuring a propagation signal based on a time during which an ultrasonic wave propagates across the flow path; a signal pattern generation section for generating a signal pattern based on a change in a propagation signal; a signal pattern storage section for previously storing a plurality of signal patterns respectively corresponding to a plurality of pieces of equipment; a signal pattern comparison section for comparing a signal pattern generated by the signal pattern generation section with a plurality of signal patterns previously stored in the signal pattern storage section; and an equipment specifying section for specifying currently used equipment among a plurality of pieces of equipment, in accordance with the comparison results obtained by the signal pattern comparison section.

Abstract: The amplifying gain is controlled by means of a data reduction equipment on the basis of the control signal input into the amplifier for amplifying the received signal propagated through the fluid and received in the ultrasonic transducer in the receiving side. The data reduction equipment includes an analog-digital converter, a processor, and a memory, wherein converted into digital data are waveform data including a peak value of each of the received signals, and the obtained digital data are stored in the memory.

Abstract: A low profile transducer (11, 12) is provided for use in flow meter for pipes of small diameter. The transducer (11, 12) has a transducer (18) or other form of transducer which transmits and receives electrical signals of three volts and 1 MHz and converts between these electrical signals and acoustic waves. In one embodiment, the transducer (18) produces surface acoustic waves (SAW), while in another embodiment the transducer (32) produces plate waves known as Lamb waves. These waves are converted to bulk acoustic waves (BAW) transmitted between the pair of transducers (11, 12).

Abstract: A method for estimating fluid flow in a conduit using a probe with four transducers is provided. The method includes generating two transit time measurements and compensating for an error angle in the transit time measurements using a predetermined compensation factor. The method further includes generating a flow measurement and estimating fluid flow based on the flow measurement.

Abstract: An ultrasonic flowmeter, wherein upstream and downstream receive signals are A/D-converted and thereby the discrete values thereof are determined; a cross-correlation between the upstream and downstream receive signals is determined; the result of calculation by correlation processing means is Hilbert-transformed; a phase relationship is determined by phase calculating means from the results of calculation by the correlation processing means and calculation by Hilbert transform; and a time difference in calculated from the phase calculation result provided by the phase calculating means through maximum value decision means.

Abstract: The flow rate of a fluid can be measured using an ultrasonic flow meter according to the present invention with a higher measuring accuracy and a lower cost. The feature of the invention consists in an ultrasonic flow meter comprising a measurement tube for flowing a fluid to be subjected to measurement, a first oscillator fitted to the outer circumference of the measurement tube, a second oscillator fitted to the outer circumference of the measurement tube at a predetermined interval along the flow of the fluid from the first oscillator and an acoustic filter fitted to the measurement tube for cutting high frequency range of the oscillating wave propagating through the oscillating tube, in which the flow rate of a fluid is measured based on a time difference between a time required when the ultrasonic wave from the upstream oscillator reaches the downstream oscillator and another time required when the ultrasonic wave from the downstream oscillator reaches the upstream oscillator.

Abstract: An ultrasonic-wave propagation time measuring method which enables determination of accurate propagation time, a gas-pressure measuring method, a gas-flow-rate measuring method, and a gas sensor. A reception wave which has been transmitted and received by an ultrasonic element 5 is shaped and integrated by an integration circuit 67 to obtain an integral value. A peak value of the integral value is held by a peak-hold circuit 39. As to detection of gas concentration, a resistance-voltage-division circuit 41 sets a reference value on the basis of the peak value, and a point in time when the integral value of the reception wave is judged by a comparator 43 to have reached the reference value is regarded as an arrival time. Subsequently, a gas concentration is detected on the basis of a period between the emission time and the arrival time.

Abstract: A process and device for measuring the velocity of flow of a fluid stream by measuring the difference between the respective traveltimes of acoustic pulses emitted by means of a generator (G) respectively between two points (PA, PB) spaced out along the fluid stream, according to whether they are propagated upstream or downstream in relation to the direction of flow, a difference that is indicative of the displacement velocity of the fluid stream. Measurement of this traveltime difference comprises using an acquisition unit (A) coupled to a processing unit (P) allowing determination of the frequency spectrum of each pulse and measurement of the phase lag affecting at least part of the frequency spectrum of each pulse, resulting from the traveltime thereof. Measurement of the velocity of flow of the fluid stream and of the resulting flow rate is very accurate. The process can be applied in chemical industries, chromatography, etc.

Abstract: An improved system for measuring the flow-rate of a gas by means of ultrasound, including a tubular element in which a plurality of openings are formed to allow one or more gas-flows to flow into the tubular element, and two or more devices for transmitting/receiving ultrasound beams. The system further includes two or more devices for focusing ultrasound beams. The transmitting/receiving devices transmit and receive, respectively, the ultrasound beams which pass through the focusing devices and the one or more gas-flows inside the tubular element and thus measure the flow-rate thereof.

Abstract: A loop flow-path is formed by providing a partition in the path of flow of a fluid duct. An incoming flow-path and an outgoing flow-path are provided with the fluid duct through connecting ducts, and a gas G flows in the fluid duct. An ultrasonic sensor having two opposing surfaces for transmission and reception is disposed in a part of the loop flow-path so that ultrasonic waves to be transmitted and receive have vector components in the direction of the loop flow-path. The ultrasonic waves outputted from the two opposing surfaces of the ultrasonic sensor travel in opposite directions to each other in the loop flow-path, one ultrasonic wave with the flow of the gas and the other ultrasonic wave against the flow of the gas, and are received on the opposite surfaces of the sensor, respectively.

Abstract: A meter includes a casing (1) with a fluid passage (2), in which two transducer mountings (3, 4) arranged at a distance (Lb) from each other support two transducers (5, 6) which are acoustically opposed to each other. Between the transducers (5, 6) there is a distance (Lu) over which they transmit and receive sound pulses through a fluid which in a direction (a) flows through the fluid passage (2). On the basis of the transit times of the sound pulses over the distance (Lu) both countercurrently with and countercurrently to the direction of flow (a), e.g. the velocity of the flow of the fluid is then calculated. A compensating device (8, 9) is arranged between at least one of the transducers (5, 6) and one of the transducer mounts (3, 4).

Abstract: An ultrasonic flowmeter includes a fluid duct including therein first and second flow-paths separated by a partition and an ultrasonic sensor provided at one end of the fluid duct. A reflecting plate provided at the other end of the fluid duct reflects ultrasonic waves generated by the ultrasonic sensor and reaching the reflecting plate through the first and second flow-paths, and returns the ultrasonic waves to the ultrasonic sensor through the second and first flow-paths, respectively, which are different from the first and second flow-paths, respectively, through which the ultrasonic waves have reached the reflecting plate. The ultrasonic flowmeter also includes first and second connecting flow-paths communicating with the first flow-path at the vicinity of one end and the other end, respectively, of the fluid duct.

Abstract: An ultrasonic flowmeter includes a flow passage and an ultrasonic transducer for measuring the flow rate in the flow passage wherein the ultrasonic transducer is equipped with a piezoelectric material having electrodes on the opposed surfaces thereof, one of which is used as an ultrasonic wave transmitting/receiving surface and faces the flow passage. The lengths of the sides of the transmitting/receiving surface is so determined that the vibration in the electrode direction is the main mode, preferably that the ratio of the lengths of the sides of the transmission/reception surface to the thickness is not greater than 0.8. Consequently, because the flow meter uses the thickness longitudinal vibration of the piezoelectric material as the main mode, the ultrasonic transducer has a high sensitivity, a high speed response and a small size and the ultrasonic flow meter has a high accuracy and is compact.

Abstract: The flow rate of a fluid can be measured using an ultrasonic flow meter according to the present invention with a higher measuring accuracy and a lower cost. The feature of the invention consists in an ultrasonic flow meter comprising a measurement tube for flowing a fluid to be subjected to measurement, a first oscillator fitted to the outer circumference of the measurement tube, a second oscillator fitted to the outer circumference of the measurement tube at a predetermined interval along the flow of the fluid from the first oscillator and an acoustic filter fitted to the measurement tube for cutting high frequency range of the oscillating wave propagating through the oscillating tube, in which the flow rate of a fluid is measured based on a time difference between a time required when the ultrasonic wave from the upstream oscillator reaches the downstream oscillator and another time required when the ultrasonic wave from the downstream oscillator reaches the upstream oscillator.

Abstract: A flow meter includes a flow path through which a fluid flows; a pair of transceivers for sending and receiving an ultrasonic wave propagating across the flow path; and a flow calculation section for calculating a flow rate of the fluid flowing through the flow path based on a result of the ultrasonic wave being sent and received by the pair of transceivers. The flow path has an equal flow speed area in which the fluid flows at a substantially equal flow speed over an entire flow rate area ranging from a high flow rate area to a low flow rate area. The pair of transceivers send and receive the ultrasonic wave so that the ultrasonic wave propagates in the equal flow speed area.

Abstract: A system for determining the density, flow velocity, and mass flow of a fluid comprising at least one sing-around circuit that determines the velocity of a signal in the fluid and that is correlatable to a database for the fluid. A system for determining flow velocity uses two of the inventive circuits with directional transmitters and receivers, one of which is set at an angle to the direction of flow that is different from the others.

Abstract: An ultrasonic flow velocity measuring method using a transit time difference of continuous sine waves without transmitting/receiving an ultrasonic pulse comprises steps of amplitude-modulating a continuous ultrasonic sine wave carrier into a lower frequency and transiting the amplitude-modulated signal, whenever the ultrasonic transit time is measured; demodulating the amplitude-modulated signal; detecting or discriminating the amplitude-modulated signal from the demodulated signal and measuring a time interval from the moment that the ultrasonic sine wave is amplitude-modulated till the amplitude-modulated signal is demodulated.

Abstract: An ultrasonic transit time flow sensor detects a signal corresponding to the phase difference between signals from two transducers during the interval of an acoustic transmission, and uses this signal to adjust an output flow rate signal in order to compensate for circuit errors inherent in the flow sensor. An Exclusive-Or phase detector detects the difference in phase between the signals resulting from the difference in propagation transit time of the flowing fluid. This measured difference includes a phase shift due to the electrical circuits of the flow sensor. In order to compensate for the circuit-induced phase shift, when the transducers are transmitting bursts of acoustic energy, the corresponding electrical signals are routed to the Exclusive-Or phase detector in order to generate a common mode DC signal representative only of the phase shift of the electrical circuits of the flow sensor.