A Step-by-Step Voltage Excitation Circuit for Measuring Ultrasonic Transit Time

Abstract

The invention relates to a circuit for measuring the transition time of ultrasonic waves by increasing voltage excitation step by step. An ultrasonic sensor is excited by the circuit through three voltage square waves with different strength so as to realize the characteristic-point positioning for a waveform peak value and calculate the transition time of a waveform. The circuit disclosed by the invention comprises a first multipath gating (4), a second multipath gating (5) and a waveform characteristic-point judging circuit (6), wherein the first multipath gating (4) is used for selecting from four alternative voltages and constructing an excitation signal, the excitation signal is sent to a sending sensor through the second multipath gating (5), and an echo signal is led into a post-processing circuit; the waveform characteristic-point judging circuit (6) is used for judging a first zero-crossing position after each peak value according to the corresponding relation of an exciting peak value and an echo peak value to obtain a transition time difference. According to the invention, characteristic points are determined by utilizing the corresponding relation of the peak values of an exciting wave and a receiving wave, in order to avoid the condition that staggering is caused by external interference on the peak value of the receiving wave, the voltage difference of the peak values is enlarged by adopting step voltage excitation, so that the anti-interference tolerance limit is increased.

Description

technical field [0001] The invention relates to a circuit for measuring the transit time of ultrasonic waves, in particular to a circuit for gradually increasing voltage excitation to measure the transit time of ultrasonic waves. Background technique [0002] The transit-time ultrasonic flowmeter relies on detecting the modulation effect of the flowing medium on the ultrasonic signal, and obtains the transit time of the sound wave on the fixed-length channel, thereby deriving the flow velocity data of the medium. At present, ultrasonic flowmeters usually judge the transit time by identifying specific mark points on the waveform, so the judgment of specific mark points on the waveform has become the key technology of time difference ultrasonic flowmeters. [0003] In the prior art, when sending out ultrasonic signals, the main methods adopted include: [0004] 1. Use equal-amplitude square wave sequence excitation, and set the threshold value. When the signal replication exc...

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Problems solved by technology

[0006] The purpose of the present invention is to solve the problem of high error rate and complex algorithm in the determination of ultrasonic zero-crossing point in the prior art, and to design a step-by-step voltage excitation method, which uses the signal amplitude to mark the corresponding relationship of the waveform and determine the ultrasonic wave. over time

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