Abstract: An ultrasonic flow velocity measuring apparatus measures a transit time under the condition a synchronization of an ultrasonic signal having a modulated frequency by PN (pseudo noise) code of a diffusion band at a transmitting side is locked at a receiving side, and prevents an excessive measurement error exceeding allowable error range. If the installation positions of the ultrasonic transducers of upper and lower stream sides are moved, an ultrasonic transit time can be precisely measured by using a different signal series PN code without changing an electronic component and a program. In addition, the ultrasonic flow velocity measuring apparatus installs a plurality of ultrasonic transducers according to various distances from the bottom of a fluid passage, and accurately measures average flow velocity which is variable in response to the height in a curved fluid passage.

Abstract: A method for detecting a phase difference is provided. The method includes selecting first and second input signals from a plurality of pairs of input signals. The method further includes modulating a duty cycle of first and second intermediate signals from a first duty cycle based on a phase difference between the first and second input signals. The method also includes creating a differential signal based on the modulated duty cycles of the first and second intermediate signals that is related to the phase difference between the first and second input signals.

Abstract: Method for determining the flow rate and/or the molecular mass of liquid or gaseous media in flow measuring instruments, especially pneumotachographs, with the aid of the measurement of the transit time of ultrasonic pulses in the medium between two ultrasonic transmitters/receivers, especially piezoelectric transmitters/receivers, where an ultrasonic impulse is emitted from a transmitter (1), and simultaneously the run of a time duration starts which is slightly shorter than the transit time in the static medium, after the end of the time duration the discharge of a capacitor, to which a voltage is applied, commences with a constant current intensity, the discharge is terminated with the registration of the ultrasonic pulse in the receiver (2), the voltage still applied to the capacitor is measured and the discharge time is determined, the transit time from the time duration and the discharge is added up, the measurement of the transit time is repeated in the opposite direction, and the flow rate and/or the

Abstract: An ultrasonic transit time flow sensor employs two transducers spaced out along a direction of fluid flow. A variable frequency acoustic signal is simultaneously transmitted by both transducers in a burst. After an interval corresponding to the expected transit time between transducers, both transducers are switched to their respective receiving states and a phase difference between their received signals is used as measure of the fluid rate. The invention also provides a feedback arrangement for controlling the acoustic frequency to maintain stable operation under a variety of operating conditions.

Abstract: An flow rate measurement method and a ultrasonic flow meter is provided, which can measure a flow velocity accurately by utilizing a ultrasonic wave having a frequency by which a phase difference becomes zero. According to the flow rate measurement method, a reference ultrasonic velocity is prepared such that the fluid is in a standard condition, firstly. Then, an absolute ultrasonic velocity in the fluid and a temporary flow velocity V0 in the fluid are obtained. Then, the temporary flow velocity V0 is corrected by using the difference between the reference ultrasonic velocity and the absolute ultrasonic velocity thereby to determine an accurate flow velocity of the fluid, and to determine a flow rate of the fluid by using the accurate flow velocity and a cross section area of the conduit.

Abstract: A transit time ultrasonic flow meter includes a pair of ultrasonic transducers transmitting an ultrasonic signal through a fluid flowing in a conduit and receiving the transmitted ultrasonic signal. An exclusive-OR (XOR) phase comparator then detects a difference in phase between the received ultrasonic signal and a reference signal having a selected phase shift (e.g., 0°, 90°, 180°, or 270°) with respect to the transmitted ultrasonic signal. Control circuitry selects the phase shift of the reference signal based on outputs of the XOR phase comparator in order to maintain the phase shifts detected by the XOR phase comparator within a range in which the comparator has relatively accurate detection (e.g., 45° to 135°). By adjusting the phase of the reference signal and thereby maintaining the XOR phase comparator in its relatively high accuracy region, the present invention enhances the accuracy of detection by the phase comparator.

Abstract: An ultrasonic flow velocity measuring method comprises a phase difference flow velocity measuring method irrelevant to the change of the sound velocity, if a flow velocity is measured based on a phase difference method without transmitting/receiving an ultrasonic pulse in a river, an open sluice channel or a pile having a large inner diameter, including amplitude-modulating at least one continuous ultrasonic sine waves of a carrier frequench ƒC into signals of an amplitude-modulated frequench ƒM, if at least one phase difference &Dgr;&phgr;C transited and received in directions similar and contrary to the flow velocity is equal to n&pgr;+a&pgr;, obtaining n&pgr;, using the signal of the amplitude-modulation ƒM; and measuring a part of a&pgr;<&pgr;, obtaining the phase difference between the signals of the carrier frequench ƒC and obtaining the total phase differences &Dgr;&phgr;C precisely.

Abstract: A transit time ultrasonic fluid flow sensor is configured to compensate for circuit related drifts in the flow rate output signal. During acoustic transmission some of the transmitting signal is also routed through the receiving circuits from which a reference signal is derived to provide the compensating signal. In an alternate configuration, compensation or flow sensor drift is derived from reception of the round-trip signals between a pair of transducers.

Abstract: An accurate and reliable pneumotachometer with annular ring transducers for determining the velocity of a fluid flow is provided. A novel and accurate flow measurement system for measuring transit time of a fluid flow using chirp signals and a pneumotachometer with annular ring transducers is also disclosed.

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: An ultrasonic flow velocity measuring method comprises a phase difference flow velocity measuring method irrelevant to the change of the sound velocity, if a flow velocity is measured based on a phase difference method without transmitting/receiving an ultrasonic pulse in a river, an open sluice channel or a pile having a large inner diameter, including amplitude-modulating at least one continuous ultrasonic sine waves of a carrier frequench ƒC into signals of an amplitude-modulated frequench ƒM, if at least one phase difference &Dgr;&phgr;C transited and received in directions similar and contrary to the flow velocity is equal to n&pgr;+a&pgr;, obtaining n&pgr;, using the signal of the amplitude-modulation ƒM; and measuring a part of a&pgr;<&pgr;, obtaining the phase difference between the signals of the carrier frequench ƒC and obtaining the total phase differences &Dgr;&phgr;C precisely.

Abstract: An accurate and reliable pneumotachometer with annular ring transducers for determining the velocity of a fluid flow is provided. A novel and accurate flow measurement system for measuring transit time of a fluid flow using chirp signals and a pneumotachometer with annular ring transducers is also disclosed.

Abstract: Measurement of density and mass flow of disperse systems with a gas as fluid phase flowing through a pipe is carried out by introducing sound in the frequency range 20-2,000 Hz in the middle of the cross-section of the pipe. The sound has a wavelength which is at least half the pipe diameter. The speed propagation of sound waves in the flowing disperse system is is measured in the axial direction of flow over at least two transit sections of differing length; and the speed propagation of sound waves in the flowing disperse system is also measured in a direction contrary to the axial direction of flow over at least two transit sections of differing length. The fill level of a reception member in communication with a line of the disperse system is calculated from the measured mass flow rate over a period of time.