Flow measurement device
First Claim
1. A flow measurement device comprising:
- a pair of vibrators being placed across a flow path for transmitting and receiving an ultrasonic wave between them to measure a flow rate of fluid flowing through the flow path;
a transmission device that drives one of the vibrators to transmit an ultrasonic wave;
a reception unit responsive to an output signal from the other of the vibrators to convert the output signal into an electric signal representing cycles of the ultrasonic wave propagated from the one of the vibrators;
a reception wave determination unit that monitors the electric signal from the reception unit and outputs a detection signal when the wave in the cycles first becomes a predetermined value;
a reception point detection unit that detects zero-crossing points of the cycles from the electric signal;
a reception point storage that stores arrival times of at least two zero-crossing points detected by the reception point detection unit, wherein the stored arrival times comprise arrival times of adjacent zero-crossing points among a series of detected zero-crossing points starting from an earliest detected zero-crossing point through a last zero-crossing point detected immediately before the reception wave determination unit outputs the detection signal; and
a flow rate computation unit that calculates the flow rate based on an average of the arrival times of adjacent zero-crossing points stored in the reception point storage.
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Accused Products
Abstract
To find the propagation time of an ultrasonic wave, a difference occurs between the waveforms received upstream and downstream in a portion where the reception amplitude is comparatively large and it is prevented from being detected as an error of the propagation time. A reception signal is amplified in a reception unit 35 and reception point storage units 38 store the most recent reception point data in a plurality of storage sections in order until the signal level becomes a predetermined value (Vref). An average value of the two zero crossing points before and after the signal level becomes Vref can be adopted as a reception point, the propagation time with a small error of up and down offset, etc., is measured, and it is made possible to realize power saving operation by shortening the measurement time.
12 Citations
12 Claims
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1. A flow measurement device comprising:
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a pair of vibrators being placed across a flow path for transmitting and receiving an ultrasonic wave between them to measure a flow rate of fluid flowing through the flow path; a transmission device that drives one of the vibrators to transmit an ultrasonic wave; a reception unit responsive to an output signal from the other of the vibrators to convert the output signal into an electric signal representing cycles of the ultrasonic wave propagated from the one of the vibrators; a reception wave determination unit that monitors the electric signal from the reception unit and outputs a detection signal when the wave in the cycles first becomes a predetermined value; a reception point detection unit that detects zero-crossing points of the cycles from the electric signal; a reception point storage that stores arrival times of at least two zero-crossing points detected by the reception point detection unit, wherein the stored arrival times comprise arrival times of adjacent zero-crossing points among a series of detected zero-crossing points starting from an earliest detected zero-crossing point through a last zero-crossing point detected immediately before the reception wave determination unit outputs the detection signal; and a flow rate computation unit that calculates the flow rate based on an average of the arrival times of adjacent zero-crossing points stored in the reception point storage. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12)
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Specification