CN201837420U - Device for precisely measuring ultrasonic wave transmission time - Google Patents

Abstract

The utility model relates to a device for precisely measuring ultrasonic wave transmission time, which comprises two ultrasonic wave transducers A and B, a hardware circuit and a software subdivision algorithm. The hardware circuit mainly comprises an ultrasonic wave transducer drive circuit, an ultrasonic wave return signal filter circuit, an amplification circuit and a signal processing circuit. The signal processing circuit comprises an analog-to-digital (A/D) converter, an FPGA and a CPU. The CUP control the FPGA to start the ultrasonic wave transducer drive circuit to drive the transducer A to send an ultrasonic wave signal. The filter circuit filters and amplifies an ultrasonic wave return signal received by the ultrasonic wave transducer B. The A/D converter samples the wave return signal and stores the sampled data in a storage region constructed in the FPGA. After the sampling is completed, the CPU reads the sampled data from the FPGA and accurately calculates the transmission time of the ultrasonic wave between the two transducers A and B by adopting the software subdivision algorithm. As the FPGA-based hardware circuit and the special software subdivision algorithm are adopted, the device can realize the measurement of the ultrasonic wave transmission time with nanosecond precision and ensure good real-time.

Description

The device in a kind of precisely measuring ultrasonic wave transmission time

Technical field

The utility model belongs to sophisticated sensor and detection technique field, is specifically related to the Technology of Precision Measurement of a kind of ultrasonic transmission time.

Background technology

Hyperacoustic notable feature is the frequency height, thereby wavelength is short, and the diffraction phenomenon is little, and good directionality can direction propagation.At liquid, decay is little in the solid, penetration capacity is strong, runs into impurity or interphase and just has significant reflection.Along with development of electronic technology, ultrasonic technology more and more is applied to the precision measurement of distance, flow etc.

When ultrasound wave is propagated in fluid, downbeam and countercurrent direction transmission time different, suitable, therefore the adverse current mistiming is relevant with flow velocity, can suitable, adverse current mistiming when measuring ultrasound wave and propagate measure flow in fluid.For example, the velocity of propagation of ultrasound wave in clean water is about 1450m/s, at caliber D=300mm, under the condition of rate of flow of fluid v=1.33m/s, the concurrent-countercurrent mistiming is about 1 microsecond, guarantee to measure to reach 0.5% measuring accuracy, and the resolution of the mistiming that requirement is measured will reach and could realize 1～2 nanosecond, the Measurement Resolution in suitable, adverse current travel-time also should be in nanosecond, and even picosecond.If with conventional timer counter circuit, the frequency of clock circuit will reach 1G at least, this obviously is difficult to realize for instrument development.

Summary of the invention

The utility model discloses the method and the device in a kind of precisely measuring ultrasonic wave transmission time at the problems referred to above, adopts FPGA circuit and software segmentation interpolation algorithm, can realize nanosecond under the prerequisite that guarantees the measurement real-time, and even picosecond is measured.

The technical solution adopted in the utility model is:

The device that the utility model proposes comprises ultrasonic transducer A, ultrasonic transducer B, power amplification circuit, amplifying circuit, filtering circuit, A/D change-over circuit, D/A change-over circuit, on-site programmable gate array FPGA and central processing unit CPU;

Described ultrasonic transducer A and ultrasonic transducer B keep at a certain distance away and are oppositely arranged, exist between two transducers can propagate ultrasound waves medium;

Described central processing unit CPU connects on-site programmable gate array FPGA, control on-site programmable gate array FPGA sine wave output drive signal, one tunnel output of on-site programmable gate array FPGA connects the D/A change-over circuit, by crossing the D/A change-over circuit described sine wave drive signal is changed, the D/A change-over circuit connects power amplification circuit again, signal is amplified, power amplification circuit is connected with ultrasonic transducer A, signal is inputed to described ultrasonic transducer A, and this ultrasonic transducer A converts described this input signal to mechanical vibration and produces ultrasonic signal;

Described ultrasonic transducer B receives the ultrasonic signal that described ultrasonic transducer A sends, mechanical vibration are converted to electric signal, the output ultrasonic wave echoed signal, and by with its amplifying circuit that is connected successively, filtering circuit and A/D change-over circuit, make described ultrasonic echo signal after amplification, filtering and A/D conversion, input to on-site programmable gate array FPGA successively;

Described on-site programmable gate array FPGA sample simultaneously the sine wave drive signal of output and the ultrasonic echo signal of input, and sampled data left in the internal memory;

Described central processing unit CPU reads sampled data from the on-site programmable gate array FPGA internal memory, sine wave drive signal according to output is determined the pairing moment of ultrasonic propagation time starting point, ultrasonic echo signal according to input, employing accurately calculates the pairing moment of ultrasonic propagation time terminal point by the segmentation interpolation algorithm, and then the transmission time of accurate Calculation ultrasound wave between ultrasonic transducer A and ultrasonic transducer B.

Described transducer A is a piezoelectric transducer, can be the electrical signal conversion with certain energy mechanical vibration, and when the frequency of signal was in the frequency of ultrasonic scope, transducer A was electrical signal conversion a ultrasonic signal.Transducer B also is a piezoelectric transducer, and mechanical vibration are converted to electric signal, and when ultrasonic signal affacted on the ultrasonic transducer B, it was converted to electric signal to ultrasonic signal, and this signal can be referred to as the ultrasonic echo signal.

Described ultrasonic transducer drive circuit comprises digital-to-analog conversion (D/A) and power amplification circuit.The digital sine conversion of signals that D/A converter is used for that FPGA is sent is an analog sinus signals, and power amplification circuit is used to amplify the power of this sinusoidal signal, makes it enough energy drives ultrasonic transducer A.It is digital signal that described A/D converter is mainly used in a ultrasonic echo analog signal conversion, and the figure place of A/D converter and sample frequency are the key factors that influences ultrasonic transmission time measurement precision.

Described FPGA circuit major function has two, and first function is to produce the digital sine signal under the control of CPU, and second function is to finish the ultrasonic echo signals sampling, and the data existence is configured in the memory block of FPGA inside.

The sinusoidal ultrasonic signal of periodicity of ultrasonic transducer A emission some, after this signal is propagated in medium and is arrived transducer B, excitation transducer B produces the ultrasonic echo signal, the continuous pump of the ultrasonic signal that the amplitude of echoed signal receives along with transducer and increasing gradually, when pumping signal stops, the mechanical vibration of transducer still can continue under action of inertia and decay gradually, the amplitude of echoed signal also reduces gradually, therefore the ultrasonic echo signal is a luffing cyclical signal, and its cycle is corresponding to the cycle of ultrasonic signal.That cycle of echoed signal amplitude maximum is corresponding to the cycle of last sent that ultrasonic signal of transducer A.

Hyperacoustic travel-time is exactly the corresponding time interval between that a bit and on the echoed signal that receives of transducer B arbitrarily on the ultrasonic signal that sends of transducer A.The key of ultrasonic transmission time measurement is to determine the starting point and the terminal point in travel-time.The starting point in travel-time can be the specific pairing moment on the ultrasonic signal that sends of transducer A, the terminal point of time be on the echoed signal with corresponding that pairing moment of ultrasonic signal unique point.

Echoed signal is a Variable Amplitude cyclical signal, and the most characteristic ripple is that ripple of amplitude maximum in its waveform, can be referred to as characteristic wave, and characteristic wave is corresponding to last ripple of ultrasonic signal.In characteristic wave, the most characteristic point is zero crossing and peak point, can select the unique point of zero crossing as echoed signal.The unique point moment corresponding is exactly the terminal point in travel-time, and is corresponding with it, and the pairing moment of zero crossing of last that ripple can be defined as the starting point in travel-time in the ultrasonic signal waveform.

Because ultrasonic signal is that FPGA produces under the control of CPU, the starting point in travel-time, just the zero crossing moment corresponding of last that ripple of ultrasonic signal is easy to determine accurately that by CPU its precision depends on the running frequency of FPGA.

The terminal point in travel-time, just the pairing moment of zero crossing is determined by the segmentation interpolation algorithm in the echoed signal characteristic wave.The segmentation interpolation algorithm is according to the waveform in that cycle of peak amplitude maximum in the at first definite echoed signal of the A/D sampled signal of the ultrasonic echo of storing among the FPGA; Determine former and later two sampled points of zero crossing (ratio zero is big, and a ratio zero is little) pairing moment then; Be benchmark with former and later two sampled points of zero crossing at last, with fitting method sampled point segmented, determine the pairing moment of echoed signal zero crossing, i.e. in the pairing moment of ultrasonic propagation time terminal point, its precision depends primarily on the resolution of A/D sampling.

The utility model can be realized the measurement of the ultrasonic transmission time of nanosecond precision owing to adopted based on the hardware circuit of FPGA and special software algorithm of subdivision, and guarantees good real-time.The utility model can be widely used in adopt ultrasonic technology realize flow, apart from fields such as precision measurements.

Description of drawings

Fig. 1 is a kind of hardware block diagram of precisely measuring ultrasonic wave transmission time method;

Fig. 2 is the drive signal synoptic diagram that is added on the transducer A;

Fig. 3 is the ultrasonic echo signal schematic representation that receives on the transducer B;

Fig. 4 is a kind of working principle of hardware synoptic diagram of precisely measuring ultrasonic wave transmission time method;

Fig. 5 a-5b is a synoptic diagram of determining the corresponding moment of ultrasonic propagation time terminal point institute.

Embodiment

Below in conjunction with Figure of description the technical solution of the utility model is described in further detail.

Referring to Fig. 1, the hardware circuit of this method is mainly by ultrasonic transducer A 11, transducer B 12, central processing unit CPU 19, FPGA FPGA 18, A/D change-over circuit 17, filtering circuit 16, amplifying circuit 15, power amplification circuit 14 and D/A change-over circuit constitute.Exist between ultrasonic transducer A 11, transducer B 12 separated by a distance the placing on same the straight line, two transducers can propagate ultrasound waves medium, such as air, water, steel etc.Ultrasonic transducer is a piezoelectric transducer.

Referring to Fig. 2, be the drive signal on the ultrasonic transducer A, it is that the digital sine signal that produces in FPGA converts analog sinus signals to through the D/A change-over circuit, and then forms through the power amplification circuit amplification, the voltage of the V representation signal among the figure, t represents the time.The frequency of this signal is 1MHz, the about 10V of maximum voltage, and the about 1.5A of maximum current has about 15 watts electric energy, is enough to drive ultrasonic transducer A and converts electrical energy into mechanical energy, sends ultrasonic signal.

Referring to Fig. 3, be the ultrasonic echo signal of on transducer B, exporting, the voltage of the V representation signal among the figure, t represents the time.When the ultrasonic signal that transducer A sends was gone up through propagating into transducer B after certain travel-time, transducer B was converted to electric energy with the mechanical energy of ultrasonic signal, the output ultrasonic wave echoed signal.The electric signal of transducer B output is not before ultrasound wave propagates on the transducer B, amplitude is zero, after transducer B receives ultrasonic signal, the electric signal amplitude of output increases gradually, reduce to decay to zero then gradually, be a luffing periodic signal, that ripple of amplitude maximum is corresponding to last ripple of ultrasonic signal.The frequency of ultrasonic echo signal depends on the frequency of ultrasonic signal, also is 1MHz.

Referring to Fig. 4, after the synchronizing circuit 432 of CPU19 in FPGA18 sent the beginning sample command, FPGA18 started simultaneously to the driving of ultrasonic transducer A11 with to the sampling of ultrasonic transducer B12 output signal.

Digital sine signal generator 431 transmission frequency that are implemented in the FPGA are the sinusoidal signal in 8 cycles of 1MHz, this signal is converted to simulating signal through D/A change-over circuit 13, after power amplification circuit 14 amplifies, be carried on the transducer A11 again, send ultrasonic signal.The electric signal of transducer B12 output is connected to A/D change-over circuit 17 after wave circuit 16 filtering after amplifying through operational amplification circuit 15 after filtration.The sample circuit 433 control A/D change-over circuits 443 of FPGA inside are digital signal with analog signal conversion, and sampled value is deposited in the RAM memory block 434 that is implemented in the FPGA one by one.After sampling was finished, FPGA430 sent sampling done state information to CPU 19, and CPU19 finishes once sampling after receiving sampling done state information.

After sampling finished, CPU19 at first accurately determined the pairing moment T of starting point in the ultrasonic signal according to the data of the digital sine signal generator 431 in the FPGA _QD

CPU19 sends the read data order then, reads the data that are temporary in the RAM memory block 434, the pairing moment of accurate Calculation ultrasonic propagation time terminal point.

The pairing moment of ultrasonic transmission end time is by analyzing and calculate and realize with the segmentation interpolation algorithm all sampled datas of echoed signal.Referring to Fig. 5 a, the ultrasonic echo signal of analysis ultrasonic transducer B output for the repeatability that guarantees to measure, should extract the terminal point of ultrasonic transmission time as can be known in the waveform of peak amplitude maximum.In the complete cycle of this waveform, the most tangible two unique points are peak point and zero crossing, zero crossing are defined as the easier acquisition high precision of time reference of echoed signal.

Referring to Fig. 5 a, the computing method in the pairing moment of ultrasonic transmission end time of the present utility model are:

At first the A/D sampled point is compared in pointwise, and the maximal value of finding out sampled point just can be determined can be referred to as the eigenwert waveform to this waveform by the waveform of amplitude maximum easily;

Secondly, participate in Fig. 5 b, determine the pairing zero crossing P of ultrasonic transmission end time ₀The sampled point P in front and the sampled point P+1 in back, obviously the sampled value of sampled point P is greater than zero in characteristic wave, and the sampled value of sampled point P+1 is less than zero;

At last, as benchmark, can accurately calculate zero crossing P with sampled point P and 2 moment corresponding of P+1 with the segmentation interpolation algorithm ₀In the pairing moment, concrete computing method are as follows:

If the sample frequency of A/D is F _A/D, the time between adjacent two sampled points is to be T in the sampling period _A/DIs N from first sampled point to the hits the sampled point P, and the sampled value of sampled point P correspondence is V1, and the pairing moment of sampled point P is T1; The sampled value of sampled point P+1 correspondence is V2; The pairing moment of sampled point P is T1, sampled point P and zero crossing P ₀Between time be T2, zero crossing P ₀Moment corresponding is T _ZD, hyperacoustic transmission time is T, then:

$T_{A/D}=\frac{1}{F_{A/D}}$

$T1=N\×\frac{1}{F_{A/D}}$

In the less zone of near zero-crossing point, sinusoidal wave waveform approaches straight line, can determine T2 according to the method for linear interpolation:

$T2=\frac{1}{V2-V1}\×V1\×T_{A/D}$

Then the pairing moment of zero crossing, promptly the pairing moment of ultrasonic transmission end time is:

$T_{\mathrm{ZD}}=T1+T2=N\×\frac{1}{F_{A/D}}+\frac{1}{V2-V1}\×T_{/\mathrm{AD}}\×V1$ From following formula as can be known, the ultrasonic transmission end time corresponding resolution constantly be:

$R=\frac{1}{V2-V1}\×T_{/\mathrm{AD}}$

Participate in Fig. 5 b, the frequency of supposing the ultrasonic echo signal is 1M, and then the cycle is 1us; The resolution of A/D is 12, the amplitude of signal can be divided into 4096 parts so, if the sample frequency of A/D is 32MHz, then arrive in the negative peaked half period in the positive maximal value of sine wave, can adopt 16 points at most, if sinusoidal wave positive maximal value is regarded as straight line to the waveform in the negative peaked half period, then obviously as can be known:

$V2-V1=\frac{4096}{16}=256$

Observe sinusoidal wave positive maximal value and arrive the interior waveform of negative peaked half period as can be seen, the near zero-crossing point slope of a curve is much larger than near the slope of a curve peak value, then

V2-V1＞256

$R=\frac{1}{V2-V1}\&times;T_{/\mathrm{AD}}<\frac{1}{256}\&times;T_{/\mathrm{AD}}=\frac{1}{256}\&times;\frac{1}{32}\&times;1\mathrm{\&mu;s}=0.122\mathrm{ns}$

Referring to Fig. 5, hyperacoustic transmission time is:

$T=T_{\mathrm{ZD}}-T_{\mathrm{QD}}=N\&times;\frac{1}{F_{A/D}}+\frac{1}{V2-V1}\&times;T_{/\mathrm{AD}}\&times;V1-T_{\mathrm{QD}}$

Because the pairing moment of ultrasonic transmission start time can accurately determine, then the resolution of ultrasonic transmission time measurement depends on the resolution in the corresponding moment of ultrasonic transmission end time institute.Then the resolution of ultrasonic transmission time measurement if adopt more high-resolution A/D change-over circuit, can also realize more high-resolution measurement less than 0.122 nanosecond.

Claims (1)

1. the device in a precisely measuring ultrasonic wave transmission time, described device comprises ultrasonic transducer A, ultrasonic transducer B, power amplification circuit, amplifying circuit, filtering circuit, A/D change-over circuit, D/A change-over circuit, on-site programmable gate array FPGA and central processing unit CPU, it is characterized in that:

Described ultrasonic transducer A and ultrasonic transducer B keep at a certain distance away and are oppositely arranged, exist between two transducers can propagate ultrasound waves medium;

Described central processing unit CPU connects on-site programmable gate array FPGA, control on-site programmable gate array FPGA sine wave output drive signal, one tunnel output of on-site programmable gate array FPGA connects the D/A change-over circuit, by the D/A change-over circuit described sine wave drive signal is changed, the D/A change-over circuit connects power amplification circuit again, signal is amplified, power amplification circuit is connected with ultrasonic transducer A, signal is inputed to described ultrasonic transducer A, and this ultrasonic transducer A converts described this input signal to mechanical vibration and produces ultrasonic signal;

Described ultrasonic transducer B receives the ultrasonic signal that described ultrasonic transducer A sends, mechanical vibration are converted to electric signal, the output ultrasonic wave echoed signal, and by with its amplifying circuit that is connected successively, filtering circuit and A/D change-over circuit, make described ultrasonic echo signal after amplification, filtering and A/D conversion, input to on-site programmable gate array FPGA successively;

Described on-site programmable gate array FPGA sample simultaneously the sine wave drive signal of output and the ultrasonic echo signal of input, and sampled data left in the internal memory.

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