CN103389153A

CN103389153A - Ultrasonic wave transit time measuring circuit by secondary reflection waves

Info

Publication number: CN103389153A
Application number: CN2013103336147A
Authority: CN
Inventors: 鲍敏; 吴春华; 沈卫平
Original assignee: Zhejiang Sci Tech University ZSTU
Current assignee: Zhejiang Sci Tech University ZSTU; Zhejiang University of Science and Technology ZUST
Priority date: 2013-08-02
Filing date: 2013-08-02
Publication date: 2013-11-13
Anticipated expiration: 2033-08-02
Also published as: CN103389153B

Abstract

The invention relates to an ultrasonic wave transit time measuring circuit by secondary reflection waves. The ultrasonic wave transit time measuring circuit is used on an ultrasonic flowmeter and used for measuring the ultrasonic wave transit time between two sensors through the waveform similarity between primary received ultrasonic waves and secondary reflected ultrasonic waves. The ultrasonic wave transit time measuring circuit comprises a multi-path gating device (5), a programmable amplifier (6), waveform characteristic judging electrical systems (7-13), wherein the multi-path gating device (5) is used for ensuring that excitation signals, the primary received signals and the secondary reflected waves can accurately enter a subsequent circuit; the programmable amplifier (6) is used for processing different magnification time requirements of the primary received signals and the secondary reflected signals; the waveform characteristic judging electrical systems (7-13) are used for controlling the starting up/shutting down of a time counter (14) according to judgment results so as to complete the measurement of the transit time. According to the ultrasonic wave transit time measuring circuit, the energy source of the primary received ultrasonic waves is the same as that of the secondary reflected ultrasonic waves, so that a super-high similarity relation exists between the primary received ultrasonic waves and the secondary reflected ultrasonic waves. Thus, the problem that corresponding waveform characteristics are misjudged is avoided.

Description

A kind of circuit that utilizes secondary reflection wave measurement ultrasonic time of flight

Technical field

The present invention relates to a kind of circuit that utilizes secondary reflection wave measurement ultrasonic time of flight, be mainly used in transit-time ultrasonic flow meter, to the measurement of sound wave transit time between two subtend ultrasonic sensors.

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 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 square wave 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 was poor, may there be certain change in its amplitude in different time sections, caused threshold value can't navigate on same waveform, thereby occur unique point across cycle erroneous judgement, as shown in Figure 2 and Figure 4.

2, adopt the excitation of coded system, and detect the frequency change situation that receives 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 when working less than resonance frequency, and the electric current leading voltage embodies capacitive, and circuit embodies perceptual while greater than resonance frequency, work.The waveform that receives in real work will be difficult to desirable encoding efficiency occur, and exist obvious transition frequency composition, unique point also to be very easy to occur the cycle erroneous judgement in waveform.

Summary of the invention

The objective of the invention is, solve in prior art the ultrasound wave zero crossing is judged fault rate greatly and the problem of algorithm complexity, utilize the waveform high similarity that has cause-effect relationship once to receive ripple and secondary counter ejected wave to judge the transit time.Its concrete technical scheme is as follows:

A kind of circuit that utilizes secondary reflection wave measurement ultrasonic time of flight, use is consisting of the primary instrument of flowmeter flowmeter shell and ultrasonic sensor, comprise: excitation signal generator, produce the square-wave pulse sequence, by multi-channel gating device, be used for excitation ultrasonic sensor or ultrasonic sensor; Then successively the secondary counter ejected wave that once receives on ripple and another ultrasonic sensor on ultrasonic sensor is introduced follow-up programmable amplifier by multi-channel gating device; The highest amplitude of whole wave sequence is measured and kept to the first peak detctor; The second peak detctor passes through zero passage and constantly output can be reset on each waveform, therefore obtain the highest amplitude of single waveform; After the peak value of wave sequence is crossed peak, the output of the first peak detctor and the second peak detctor will be no longer identical, if recording both voltage differences, differential amplifier surpasses permissible value, an open window signal S7 will be exported and keep to the Second Threshold comparer, under signal S7 controls, pass through crossover point signal on first and put into follow-up time counting unit thereafter, produce a square-wave signal S8, the width of square-wave signal S8 is the transit time of two waveform character pair points.

Further, signal S2 is the threshold voltage that controlled by the flowmeter processor, and the first threshold comparer is set, and signal amplitude just can use two peak detctors after surpassing threshold voltage.

Further, rising edge detecting device and negative edge detecting device are set, produce respectively pass through crossover point signal S3 and under pass through crossover point signal S4.

The beneficial effect of patent of the present invention is: utilized the similarity that once receives ripple and secondary counter ejected wave to carry out work, evaded, in other technologies, the problem of judging by accident has easily been appearred in the zero crossing position.And the transit time data are directed to the zero crossing position of signal itself, and without any additional calculating and derivation, result has good accuracy.

Description of drawings

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

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

Fig. 3 is the schematic diagram that utilizes the square wave sequence de-energisation sensor of frequency coding 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 is pumping signal and secondary counter ejected wave A, once receive ripple B, secondary counter ejected wave amplifies the comparison of wave shape schematic diagram of C;

The signal characteristic schematic diagram of each key position in each circuit of Fig. 7;

In figure, each Reference numeral implication is: 1-flowmeter shell, 2,3-ultrasonic sensor, 4-excitation signal generator 5-multi-channel gating device, 6-programmable amplifier, 7-first threshold comparer, 8-rising edge detecting device, 9-negative edge detecting device, 10-the first peak detctor, 11-the second peak detctor, 12-differential amplifier, 13-Second Threshold comparer, 14-time counter.

Embodiment

The invention will be further described below in conjunction with accompanying drawing.

Utilization of the present invention has the causal waveform that once receives ripple and secondary counter ejected wave, uses to the judgement reference point of amplitude peak as both, open judges window, and thereafter waveform on passed through zero position position as a comparison, calculate the transit time., in order to realize above logical relation, be provided with in Circuits System: the first peak detctor 10 is measured the highest amplitude of whole wave sequence; The second peak detctor 11 passes through the zero passage output of constantly resetting on each waveform, thereby obtains the highest amplitude of single waveform.After peak value was crossed peak, both relatively exported as window signal, detected on first that is right after thereafter and passed through crossover point signal, controlled the clock start and stop, reached the measurement purpose.Rising edge detecting device 8, negative edge detecting device 9 are used for providing the up and down crossover point signal to other parts of circuit.

As shown in Figure 1, the circuit that utilizes secondary reflection wave measurement ultrasonic time of flight of the present invention uses and is consisting of the primary instrument of flowmeter flowmeter shell 1 and

ultrasonic sensor

2,3; Circuit part comprises: excitation signal generator 4, produce the square-wave pulse sequence, be used for encouraging ultrasonic sensor 2 or 3(to be assumed to be 2 here by multi-channel gating device 5), then successively the secondary counter ejected wave that once receives on ripple and ultrasonic sensor 2 on ultrasonic sensor 3 is introduced follow-up programmable amplifier 6 by multi-channel gating device 5, programmable amplifier 6 is output as signal S1 and enters subsequent processes.The signal waveform of each key component as shown in Figure 7.

Signal S2 is the threshold voltage that controlled by the flowmeter processor, and first threshold comparer 7 is set, and signal amplitude just can use two

peak detctors

10 and 11 after surpassing threshold voltage.

In circuit, the zero crossing position of passing through up and down of waveform is all important judgement key element, so is provided with rising edge detecting device 8 and negative edge detecting device 9 in circuit, produce respectively pass through crossover point signal S3 and under pass through crossover point signal S4.

The highest amplitude of whole wave sequence is measured and kept to the first peak detctor 10, until extraneous reset indication is arranged, and as S5; The second peak detctor 11 passes through zero passage and constantly output can be reset on each waveform, therefore can only obtain the highest amplitude of single waveform, as S6.After the peak value of wave sequence is crossed peak, the first peak detctor 10 and both output of the second peak detctor 11 will be no longer identical, surpass permissible value if differential amplifier 12 records both voltage differences, an open window signal S7 will be exported and keep to Second Threshold comparer 13.Under signal S7 controls, pass through crossover point signal on thereafter first and put into follow-up time counting unit 14, produce a square-wave signal S8, the width of S8 is the transit time of two waveform character pair points.

the present invention's use once receives ripple and the secondary counter ejected wave is judged, during flowmeter work, at first send pumping signal, after being delivered to the subtend sensor, the subtend sensor can collect a waveform (once receiving ripple), and can reflect simultaneously a waveform to former stimulus sensor, the waveform that this moment, former stimulus sensor will receive is exactly the secondary counter ejected wave, the invention has the advantages that once receiving ripple and secondary counter ejected wave has very direct cause-effect relationship (be all by homology mechanical wave produce) on energy, once reception ripple and secondary counter ejected wave similarity after amplifying are very large, as shown in Figure 6.Therefore circuit of the present invention has better original signal basis and unique point differentiation stability in work.

Circuit of the present invention utilizes two high once reception ripple and second trip echos of similarity degree to compare in the course of the work, can effectively avoid in prior art finding the corresponding Problem-Error that corresponding relation may exist in square wave sequence and sinusoidal wave sequence.

Claims

1. circuit that utilizes secondary reflection wave measurement ultrasonic time of flight, use is consisting of the primary instrument of flowmeter flowmeter shell (1) and ultrasonic sensor (2,3), comprise: excitation signal generator (4), produce the square-wave pulse sequence, by multi-channel gating device (5), be used for excitation ultrasonic sensor (2) or ultrasonic sensor (3); Then successively the secondary counter ejected wave on the once reception ripple on ultrasonic sensor (2,3) and another ultrasonic sensor (2,3) is introduced follow-up programmable amplifier (6) by multi-channel gating device (5); The highest amplitude of whole wave sequence is measured and kept to the first peak detctor (10); The second peak detctor (11) passes through zero passage and constantly output can be reset on each waveform, therefore obtain the highest amplitude of single waveform; After the peak value of wave sequence is crossed peak, the first peak detctor (10) and both output of the second peak detctor (11) will be no longer identical, if recording both voltage differences, differential amplifier (12) surpasses permissible value, an open window signal S7 will be exported and keep to Second Threshold comparer (13), under signal S7 controls, pass through crossover point signal on first and put into follow-up time counting unit (14) thereafter, produce a square-wave signal S8, the width of square-wave signal S8 is the transit time of two waveform character pair points.

2. the circuit that utilizes secondary reflection wave measurement ultrasonic time of flight as claimed in claim 1, it is characterized in that: signal S2 is the threshold voltage that controlled by the flowmeter processor, first threshold comparer (7) is set, and signal amplitude just can use two peak detctors (10,11) after surpassing threshold voltage.

3. the circuit that utilizes secondary reflection wave measurement ultrasonic time of flight as claimed in claim 1 is characterized in that: rising edge detecting device (8) and negative edge detecting device (9) are set, produce respectively pass through crossover point signal S3 and under pass through crossover point signal S4.