CN103471668A

CN103471668A - Circuit for measuring transition time of ultrasonic wave by increasing voltage excitation step by step

Info

Publication number: CN103471668A
Application number: CN2013103339785A
Authority: CN
Inventors: 沈卫平; 鲍敏; 郑锡斌; 吴春华
Original assignee: Zhejiang Sci Tech University ZSTU
Current assignee: Zhejiang Sci Tech University ZSTU; Zhejiang University of Science and Technology ZUST
Priority date: 2013-09-23
Filing date: 2013-09-23
Publication date: 2013-12-25
Anticipated expiration: 2033-09-23
Also published as: CN103471668B

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

The circuit of ultrasonic time of flight is measured in a kind of excitation of boosted voltage step by step

Technical field

The present invention relates to a kind of circuit of measuring ultrasonic time of flight, specifically the circuit of ultrasonic time of flight is measured in a kind of excitation of boosted voltage step by step.

Background technology

Transit-time ultrasonic flow meter relies on and detects the modulating action of flow media to ultrasonic signal, obtains the transit time of sound wave on the regular length sound channel, thereby extrapolates the flow speed data of medium.Current ultrasonic flow meter is usually taked the specific markers point identification of waveform is judged to the transit time, therefore the judgement of specific markers point on waveform has just been become the gordian technique of transit-time ultrasonic flow meter.

In prior art, when sending ultrasonic signal, the main method of taking comprises:

1, adopt the excitation of constant amplitude square sequence, and threshold value is set, after signal replication surpasses threshold value, adopt the zero crossing position of several waveforms thereafter as feature locations.This method is applied and is had certain difficulty in gas time difference type flowmeter, when flow stability is poor, may there be certain change in its amplitude in different time sections, causes threshold value can't navigate on same waveform, thereby judging by accident across the cycle of unique point occur.As shown in Figure 2 and Figure 4.

2, adopt with the excitation of frequency coding constant amplitude square, and detect the frequency change situation received in waveform, determine the waveform character point by the corresponding relation with the excitation coding, as shown in Figure 3 and Figure 5.This mode is used more on radar, but uses some problems is arranged on ultrasonic sensor.Ultrasonic sensor can obtain best output situation on its resonant frequency point, but adopts coded excitation just inevitably need to depart from its resonance frequency.Ultrasonic sensor is being less than resonance frequency when work, and the electric current leading voltage embodies capacitive, and circuit embodies perception while being greater than resonance frequency work.The waveform received in real work will be difficult to desirable encoding efficiency occur, and in waveform, exist obvious transition frequency composition, unique point also to be very easy to occur the cycle erroneous judgement.

Summary of the invention

The objective of the invention is to solve in prior art the ultrasound wave zero crossing is judged to fault rate greatly and the problem of algorithm complexity, design a kind of motivational techniques of boosted voltage step by step, utilize signal amplitude to carry out the corresponding relation of mark waveform, determine ultrasonic time of flight.The technical scheme of the employing that it adopts is: the circuit of ultrasonic time of flight is measured in a kind of excitation of boosted voltage step by step, primary instrument for flowmeter shell and two ultrasonic sensor formation flowmeters, comprise: the first multi-channel gating device produces and strengthens step by step voltage excitation signals; The second multi-channel gating device, realize excitation and receive the switching of signal between described two ultrasonic sensors by described the second multi-channel gating device; Waveform character point decision circuit input signal with receive signal, and utilize waveform peak-peak wherein to determine both corresponding relations, and pass through zero crossing and constantly subtract each other as the transit time on thereafter first; Transit time filtering follower, by after the smothing filtering as a result of described waveform character point decision circuit input, is realized output.

Further, adopt 1.8 ~ 3.3V to make the starting of oscillation of sonac.

Further, use the 5V voltage drive.

Further, operating voltage is 20～24V.

Further, the signal of excitation ultrasonic sensor has the square wave sequence of four voltages.

The beneficial effect of patent of the present invention is that the judgment basis using amplitude as the waveform anchor point carries out work, has evaded in other technologies and the problem of erroneous judgement the zero crossing position easily occurred to.And, by widening the gap between maximum excitation voltage and other voltage, strengthening flows causes the tolerance limit that signal amplitude changes, and increases the stability of judging characteristic point.

This circuit is constructed in the course of the work one and is had the square wave sequence of boosted voltage amplitude step by step, thereby, from utilizing excitation and receiving waveform and determine both corresponding relations at the corresponding relation of peak value, this principle of work can effectively be avoided in prior art at constant amplitude square sequence and corresponding Problem-Error that in sinusoidal wave sequence, the searching corresponding relation may exist.

The accompanying drawing explanation

Fig. 1 is the electric circuit constitute structural representation of the present invention;

Fig. 2 is the schematic diagram that the square wave sequence de-energisation sensor of amplitude fixed frequency such as utilizes in prior art;

Fig. 3 is the schematic diagram that the square wave sequence de-energisation sensor of amplitude frequency coding such as utilizes in prior art;

Fig. 4 utilizes single threshold method to judge the schematic diagram of waveform character point in prior art;

Fig. 5 is the schematic diagram that utilizes the frequency change judgement waveform character point in waveform in prior art;

Fig. 6 strengthens voltage excitation signals and the comparison of wave shape schematic diagram that receives signal step by step.

In figure, each Reference numeral implication is: the 1-flowmeter shell; 2,3-ultrasonic sensor; 4-the first multi-channel gating device; 5-the second multi-channel gating device; 6-waveform character point decision circuit; 7-transit time filtering follower.

Embodiment

Below in conjunction with accompanying drawing, the invention will be further described.

The circuit of ultrasonic time of flight is measured in the excitation of boosted voltage step by step of the present invention, constructs three grades of square wave sequences that voltage magnitude increases step by step, pulls open the driving voltage difference of each inter-stage simultaneously as far as possible.In receiving signal, also can correspondingly produce amplitude difference, thereby can, using this parameter as the mark with the corresponding waveform of pumping signal, realize the measurement of transit time.In order to realize above logical relation, in Circuits System, be provided with: the first multi channel selecting 4, the square wave sequence increased step by step for constructing voltage magnitude; The second multi channel selecting 5 switches driving voltage and reception signal on two ultrasonic sensors, realizes the time and tide test; Waveform character point decision circuit 6 needs input signal and receives signal, and utilizes waveform peak-peak wherein to determine both corresponding relations, and passes through zero crossing and constantly subtract each other as the transit time on thereafter first; Transit time filtering follower 7 is realized output after waveform character is put to the smothing filtering as a result of decision circuit 6 inputs.

As shown in Figure 1, flowmeter shell 1 and

ultrasonic sensor

2,3 form the primary instrument of flowmeters to the circuit structure of the excitation of boosted voltage step by step measurement ultrasonic time of flight of the present invention; Circuit part of the present invention comprises: the first multi-channel gating device 4 produces and strengthens step by step voltage excitation signals; Realize excitation and receive the switching of signal between two

ultrasonic sensors

2,3 by the second multi-channel gating device 5, reaching the purpose that time and tide is measured; Waveform character point decision circuit 6 needs input signal and receives signal, and utilizes waveform peak-peak wherein to determine both corresponding relations, and passes through zero crossing and constantly subtract each other as the transit time on thereafter first; Transit time filtering follower 7 is realized output after waveform character is put to the smothing filtering as a result of decision circuit 6 inputs.The signal waveform of each key component as shown in Figure 6.

In enforcement, alternative voltage is designed to respectively: 1.8 ~ 3.3V, and this small voltage excitation is the starting of oscillation for sonac, then uses the 5V voltage drive, last operating voltage is that 20～24V voltage produces a crest voltage mark.Above voltage all has existence in the conventional ultrasound flowmeter electronics, and has widened the difference between crest voltage and other voltage as far as possible, can obtain peak value mark effect preferably.Can find out more clearly driving voltage in Fig. 6 and receive the waveform corresponding relation between signal, after peak value occurs, on thereafter first, pass through the zero crossing position, signal corresponding point are calculated the transit time.Thereafter reception waveform is that sensor freely shakes, and no longer receives.

The present invention uses boosted voltage excitation step by step, and judges unique point according to the highest amplitude corresponding relation received between ripple and excitation waveform.The invention has the advantages that the very obvious amplitude of utilization changes to determine corresponding point, cause that for fear of flow fluctuation signal amplitude changes simultaneously, maximum excitation voltage and other magnitudes of voltage are pulled open to larger gap, strengthening flows causes the tolerance limit that signal amplitude changes, and increases the stability of judging characteristic point.

Claims

One kind step by step boosted voltage excitation measure the circuit of ultrasonic time of flight, form the primary instrument of flowmeter for flowmeter shell (1) and two ultrasonic sensors (2,3), comprise: the first multi-channel gating device (4) produces and strengthens step by step voltage excitation signals; The second multi-channel gating device (5), realize excitation and receive the switching of signal between described two ultrasonic sensors (2,3) by described the second multi-channel gating device (5); Waveform character point decision circuit (6) input signal with receive signal, and utilize waveform peak-peak wherein to determine both corresponding relations, and pass through zero crossing and constantly subtract each other as the transit time on thereafter first; Transit time filtering follower (7), by after the smothing filtering as a result of described waveform character point decision circuit (6) input, is realized output.
2. the circuit of ultrasonic time of flight is measured in the excitation of boosted voltage step by step as claimed in claim 1, it is characterized in that: adopt 1.8 ~ 3.3V to make the starting of oscillation of sonac.
3. the circuit of ultrasonic time of flight is measured in the excitation of boosted voltage step by step as claimed in claim 1, it is characterized in that: use the 5V voltage drive.
4. the circuit of ultrasonic time of flight is measured in the excitation of boosted voltage step by step as claimed in claim 1, and it is characterized in that: operating voltage is 20～24V.
5. the circuit of ultrasonic time of flight is measured in the excitation of boosted voltage step by step as claimed in claim 1, and it is characterized in that: the signal of excitation ultrasonic sensor has the square wave sequence of four voltages.