JP3068674B2 - Ultrasonic transducer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultrasonic wave transmitting and receiving apparatus for transmitting an ultrasonic wave to an object to be measured and measuring the propagation time and the like.

[0002]

2. Description of the Related Art Generally, an ultrasonic measuring instrument such as an ultrasonic distance meter or an ultrasonic flow meter outputs an ultrasonic wave of a predetermined frequency from an ultrasonic transmitter and reflects a reflected wave or a transmitted wave. It is configured to capture and convert it into an electrical signal, and calculate the propagation time and the like based on the captured reception information. FIG. 13 shows a conventional example of an ultrasonic wave transmitting / receiving apparatus which is one of such ultrasonic measuring instruments.

In the conventional example shown in FIG. 13, a pulse oscillation circuit 101 for generating and outputting a pulse wave at predetermined timing by a timer built in advance, and an ultrasonic wave transmission driven by the pulse oscillation circuit 101 Vessel 102
And an ultrasonic wave receiver 103 that receives an ultrasonic wave output from the ultrasonic wave transmitter 102 via the device under test S. The ultrasonic signal received by the ultrasonic receiver 103 is converted into an electric signal, amplified by the amplifier 104, and sent to the propagation time calculating means 106. The propagation time calculating means 106 calculates the propagation time from the received signal from the amplifier 104 and the timing pulse from the timer of the pulse oscillation circuit 101.

FIG. 14 shows the above-mentioned propagation time calculating means 10.
6 shows a specific example. The propagation time estimating means 106 includes a timing control circuit 110 which is triggered by a timing pulse from a timer of the pulse oscillating circuit 101 to generate a write pulse and a read pulse which are square wave pulses of a fixed period, A / D that inputs a signal as waveform data, converts it into a digital value, and outputs it
A conversion circuit 111, a waveform storage unit 112 that stores the waveform data output from the A / D conversion circuit 111 at a predetermined address as a write pulse and reads and outputs the read data as a read pulse, and And a propagation time calculation output unit 113 for detecting and outputting the propagation time from the output waveform data.

A propagation time calculation output section 113 detects a zero cross point of the received signal from the waveform data output from the waveform storage section 112 and outputs a zero cross point address detection section 114 for outputting an address corresponding to the zero cross point.
And a propagation time calculator 117 for calculating a propagation time based on the address output from the zero-cross point address detector 114.

In the conventional example shown in FIG. 14, first, an output pulse from the pulse oscillation circuit 101 shown in FIG. 13 is input to the timing control circuit 110 as a timing pulse. A square wave pulse having a constant period triggered by the timing pulse is output from the timing control circuit 110 as a write pulse. on the other hand,
The A / D conversion circuit 111 samples the transmitted waveform data according to the write pulse, converts the data into digital data, and outputs the digital data to the waveform storage unit 112. The digital value output to the waveform storage unit 112 is
In, data is sequentially stored from a lower address according to a write pulse.

When all the necessary digital values are stored, the timing control circuit 110 outputs a read pulse. With this read pulse, the digital values stored in the waveform storage unit 112 are read out in the same order in which they were written, and sent to the zero-crossing point address detection unit 114. FIG. 15 shows a timing chart of writing and reading.

In the zero-crossing point address detecting section 114,
A predetermined level waveform is detected from the waveform data based on a predetermined threshold level Th, and a digital value whose polarity changes from positive to negative is detected first among digital values output after the detection. Then, this is output as a zero-cross point (information indicating the reception timing of the received ultrasonic wave).

Then, the propagation time calculation unit 11 receiving this signal
In No. 7, the propagation time of the received ultrasonic wave is calculated based on the zero cross point (information indicating the reception timing of the received ultrasonic wave) specified by the zero cross point address detection circuit unit 114. FIG. 15 shows the relationship among the timing pulse _Po , the received ultrasonic signals A, B, C, the threshold level Th, and the like. In FIG. 15, the time t _O
Is detected because of the rise time t of the true received signal.
Since the received signal of the s portion is buried in the nozzle, and it is difficult to detect the rising of the received signal accurately,
The reception time is defined as the first zero-cross point t _{O where} detection is reliable. Also, if necessary, the second and third zero-cross points are detected, and based on this, the error between ts and t _O , that is, “ts−t _O ”, is corrected, and the received signal rise time ts
, The ultrasonic propagation time in the object S may be measured.

[0010]

However, in such a conventional example, if the reception level of the received signal fluctuates, the time t _O described above is erroneously detected even for the same DUT. There is a problem that it is. As shown in the third waveform B from the top in FIG. 15, when the reception level of the reception signal decreases, the time t _O detects a delayed time. When the reception level of the reception signal increases as shown in the fourth waveform C from the top in FIG. 15 (FIG. 15), the time t _O detects an earlier time. As described above, since the detection is performed with the time t _O shifted, there is a disadvantage that a measurement error occurs in the ultrasonic propagation time in the object S.

[0011]

SUMMARY OF THE INVENTION It is an object of the present invention to provide an ultrasonic wave transmitting / receiving apparatus which solves the disadvantages of the conventional example and which does not cause a measurement error in the ultrasonic wave propagation time even if the received signal fluctuates. Is its purpose.

[0012]

In order to achieve the above object, according to the present invention, there is provided an ultrasonic wave transmitter and an ultrasonic wave receiver, and an ultrasonic wave receiver is provided based on an output timing of the ultrasonic wave transmitter. And a propagation time calculating means for calculating a propagation time of the ultrasonic wave received by the detector. The propagation time calculating means includes a waveform storage unit that sequentially stores the waveform signals of the ultrasonic waves received by the ultrasonic receiver at a predetermined timing, and a zero cross point based on the waveform data output from the waveform storage unit. It has a zero-cross position detecting section for detecting, and a propagation time calculating section for calculating the propagation time of the received ultrasonic wave based on the output of the zero-cross position detecting section and the output timing of the ultrasonic transmitter. The zero-crossing position detecting unit has a zero-crossing point tracking function for detecting the zero-crossing point of the received waveform data based on the zero-crossing point of the previously measured and specified waveform data. . This aims to achieve the above-mentioned object.

[0013]

According to the present invention, since the zero-cross point is determined based on the zero-cross point of the previous waveform data, tracking can be performed effectively without a sudden change in propagation time when performing a plurality of measurements. Therefore, even when the level of the received signal fluctuates, the zero-cross point does not change. Also, by adding a method of reconsidering the zero-cross point by obtaining a correlation with the reference waveform data by periodic interrupt processing or the like, for example, tracking of a different zero-cross point can be reliably prevented.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a first embodiment of the present invention will be described with reference to FIGS. Here, the same reference numerals are used for the same components as those in the conventional example described above.

First, as shown in FIG. 2, in this embodiment, a pulse oscillation circuit 101, an ultrasonic transmitter 102 driven by the pulse oscillation circuit 101, and an output from the ultrasonic transmitter 102 An ultrasonic wave receiver 103 for receiving ultrasonic waves via the device under test S; The ultrasonic signal received by the ultrasonic receiver 103 is converted into an electric signal, then amplified by the amplifier 104, and sent to the propagation time calculating means 10. Then, the propagation time calculating means 10
Now, the reception signal from the amplifier 104 and the pulse oscillation circuit 1
The propagation time of the received ultrasonic wave is calculated from the timing pulse from 01.

FIG. 1 shows a specific example of the propagation time calculating means 10. The propagation time estimating means 10 shown in FIG.
10 and an A / D conversion circuit 111. And
A waveform storage unit 11 for storing the waveform data output from the A / D conversion circuit 111 at a predetermined address with a write pulse and reading and outputting the read data with a read pulse;
A zero-cross position detecting unit 1 for detecting a zero-cross point of a trigger wave from the waveform data output from the waveform storage unit 11.
2, and a propagation time calculation unit 13 that calculates and outputs a propagation time from the waveform data output from the zero cross position detection unit 12 and the waveform storage unit 11.

In this embodiment, the zero-cross position detecting unit 12
However, it further includes an initial zero-cross detecting unit 121 and a zero-cross tracking unit 122.

The initial zero-cross detector 121 detects a zero-cross point address of a trigger wave serving as a reference.
It is usually performed in the preparation stage of measurement. As a method for obtaining the zero-cross point, a method previously obtained by a known method can be adopted. On the other hand, for example, the amplitude ratio between adjacent waves may be obtained from the waveform data of the received wave, and the zero-cross point address may be detected based on the relationship with the wave having the maximum amplitude ratio. According to this method, it is possible to perform measurement based on the true arrival from the received signal. As another method, an average of a plurality of waveform data may be averaged, and in the averaged waveform data, an address that crosses zero after a waveform exceeding a certain threshold level may be used as a reference zero-cross address.

Next, a case where the detailed structure of the zero-cross tracking unit 122 is signal-processed by a microcomputer will be described. Therefore, the algorithm will be described with reference to the algorithm shown in FIG. 3 and the enlarged waveform diagram near the zero cross point shown in FIG.

First, in the waveform data received this time, a waveform W _{z, p-1} having the same address as the address z _p-1 of the reference zero cross point of the trigger wave in the previous waveform data is obtained (S1-1). Since there is some variation in each reception, the data value at the address of the previous zero-cross point is not always 0. Therefore,
It is determined which of the zero cross points has shifted by seeing this shift (S1-2).

[0021] That is, when the waveform data W _{Z, p-1} is 0 or more, it is judged that the zero crossing point as shown in FIG. 4 is shifted backward, the waveform toward the address z _p-1 to the rear code data from + - seeking address change to be the address z _p and the reference zero-cross point of the new trigger wave (S1-3). On the other hand, if the waveform data W _{z, p-1} is less than 0, determines the zero-crossing point as shown in FIG. 5 as shifted forward, the waveform data forward from the address z _p-1 code Find the address where-changes from-to +,
The address z _p and the reference zero-cross point of the new trigger wave (S1-4). In this way, since the current zero-cross point is determined based on the address of the previous zero-cross point, tracking of the zero-cross point can be performed as long as there is no sudden change in the propagation time. Also, the zero cross point does not change.

Next, a second embodiment of the present invention will be described with reference to FIGS. Here, the same reference numerals are used for the same components as those in the first embodiment described above.

In FIG. 6, reference numeral 20 indicates another specific example of the propagation time calculating means. The propagation time calculating means 20 in FIG. 6 has a configuration including a new reviewing unit 14. As shown in FIG. 7, the review unit 14 includes a reference waveform pattern calculation storage unit 140 and an average waveform pattern calculation storage unit 141, and the reference waveform pattern calculation storage unit 1
A correlation calculation unit 142 that receives the output signals of the average waveform pattern calculation storage unit 141 and performs a predetermined calculation, and a zero-cross correction unit 1 that corrects the output of the correlation calculation unit 142.
43.

The average waveform pattern storage section 141 stores the average pattern of the waveform at the measurement stage. This algorithm is shown in FIG. In the present embodiment, the zero cross points of the four forward waves are obtained by the following equation based on the zero cross points of the trigger wave obtained by the zero cross tracking unit 122 (S4-2).

Z _j (i) = Z _{t, i−} W · (4-j);
[Where j = 0,..., 3] Here, W is the average wavelength of the waveform data stored in the reference waveform pattern storage unit 140. Further, the four zero-cross points can be obtained by detecting an address whose sign changes from the raw waveform data. However, in this case, the four zero-cross points are obtained by an approximate expression using a wavelength to shorten the processing time. Furthermore, a point (expected + peak point) １ ／ wavelength before each zero cross point and 3
The data difference between the point / 4 wavelength before (predicted-peak point), that is, the span, is obtained from the following equation (S4-3).

S _j (i) = W _{zj-1w / 4} (i) −W _{Zj-3w / 4} (i)

Here also, by the same approximation as described above,
The processing time is shortened by approximating that a １ ／ wavelength before the zero cross point is a + peak point and a 、 ３ wavelength before is a − peak point. Obtaining the actual peak value is of course also possible. Here, by taking the difference between the peak point of + and the peak point of-, the span can cancel the influence of the offset value and low frequency noise superimposed on the waveform data.

From this step "S4-2" to "S4-
The steps up to "4" are repeated for the n pieces of received waveform data, and the span of each of the four waves is integrated (S4-4).

A _j (i) = A _j (i−1) + S _j (i); [where j = 0,... 3] Next, an average span is determined from the integrated value of the span of each of the four waves. (S4-6).

Average value of S _j = A _j (n) / n; [where j = 0,... 3]

The reference waveform pattern storage section 140 stores reference waveform pattern information in a preparation stage for measurement. The method of obtaining the reference waveform pattern is to obtain the average span Rj and the average wavelength w of the waveform in a stable state before the measurement and store the data in a stable state before the measurement by the same method as the above-described method of obtaining the average waveform.

Here, an example of an algorithm for obtaining the average wavelength will be described with reference to FIG. First, the ith (i
= 1,... N), the maximum value of the sign + is detected, and the address “max” is detected.
(I) "(S2-2). The address "max
(I) "zero _j (i) (j = 0...)" And each peak of the waveform at the point where the sign of the value of the waveform data changes from-to + from the previous address (zero cross point) The value “P _j (i)” is obtained (S2-4). This step "S2-4" with continued until the peak value "Pj (i)" is less than the threshold level P _Th (S2-
5) The number C of waves whose peak value is larger than the threshold level P _Th is obtained (S2-6). Then, the wavelength L of the i-th waveform data is

L (i) = [zero _O (i) -zero
_C (i)] / C; (S2-7). Steps “S2-2” to “S2-7” are repeated for n pieces of received waveform data, and each wavelength L
(I) is obtained (S2-1, S2-8).

The average wavelength w is: w = (1 / n)
ΣL (i); is obtained by the equation (S2-9).

The correlation calculation section 142 performs a correlation calculation between the reference waveform pattern information stored in advance from the reference waveform pattern storage section 140 and the current waveform pattern information stored from the average waveform pattern storage section 141. Then, the zero-cross correction unit 143 corrects the zero-cross point of the trigger wave based on the calculation result of the correlation calculation unit 142.

FIG. 12 shows the algorithm of the correlation operation section 142 and the zero-cross correction section 143. In FIG. 12, first, a correlation operation between the average waveform pattern and the reference waveform pattern is performed based on the following equation, and the deviation is obtained.

D _k = (1/4) Σ (average value of R _{k + j} −S _j ) ² ; This D _k is _obtained for k = −1, 0, 1 and its minimum value is It is determined (S5-5).

When the deviation D _-1 is the smallest, it is determined that the trigger wave currently being tracked is shifted, the trigger wave is shifted one wave before, and the zero-cross point of the trigger wave is set to "Z
_p = Z _p -W "and to (S5-7). On the other hand, if the deviation D _-1 is not the minimum value, it is determined that the trigger wave is shifted in the direction opposite to the direction currently being tracked, and the trigger wave is shifted one wave later, and the zero cross point of the trigger wave is shifted. ; “Z _p
= And Z _p + w "(5-9). When D _O is the minimum value, it is determined that the trigger wave currently being tracked is correct, and the trigger wave is left as it is.

By starting the review unit 14 configured as described above at regular intervals, a review operation of the trigger wave currently being tracked is performed. According to this algorithm, the correlation between the reference waveform pattern and the average waveform pattern is shifted by one wave on the left and right sides, and when the deviation becomes the minimum value, it is determined that the waveforms match.

As described above, by providing the review unit 14, it is possible to prevent the zero-cross point tracking unit 122 from tracking the wrong zero-cross point of the trigger wave. Here, the zero cross point in the above embodiment is mainly a point where the sign of the data changes from + to-, but the sign changes from-to +.
The same applies to the point that changes to. The other configuration and operation and effect are the same as those of the first embodiment.

[0041]

Since the present invention is constructed and functions as described above, according to the present invention, since a zero cross position detecting section for determining a zero cross point based on the zero cross point of the previous waveform data is provided, a plurality of measurements can be performed. As long as there is no sudden change in the propagation time, the zero-cross point of the trigger wave can be accurately detected. Therefore, even when the level of the received signal changes, the zero-cross point does not change. Also, if the zero-cross point is reviewed by calculating the correlation with the reference waveform data by periodic interrupt processing or the like, tracking related to a different zero-cross point can be effectively prevented.
It is possible to provide an unprecedented excellent ultrasonic wave transmitting / receiving apparatus capable of reducing the error of the propagation time measurement.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a main part of a first embodiment of the present invention.

FIG. 2 is a block diagram showing the configuration of the entire apparatus incorporating the block diagram of FIG. 1;

FIG. 3 is a flowchart showing an algorithm of a zero-cross tracking unit in FIG. 1;

FIG. 4 is an explanatory diagram showing a physical meaning of one operation direction in FIG. 3;

5 is an explanatory diagram showing the physical meaning of the other operation direction in FIG.

FIG. 6 is a block diagram showing another example of the propagation time calculating means in the second embodiment of the present invention.

FIG. 7 is a block diagram showing a specific example of a review unit in the block diagram of FIG. 6;

8 is a flowchart showing the operation of a reference waveform pattern calculation storage unit in FIG. 7;

FIG. 9 is an explanatory diagram showing the meaning of the i-th wave in FIG. 7;

FIG. 10 is a flowchart showing the operation of the average waveform pattern calculation storage unit in FIG. 7;

11 is a flowchart showing the operation of the correlation calculation unit and the zero-cross correction unit in FIG.

FIG. 12 is an explanatory diagram showing a review operation during the operation of FIG. 7;

13 and 14 are block diagrams showing a conventional example.

FIG. 15 is an explanatory diagram showing the operation of FIG.

[Explanation of symbols]

 10, 20 Propagation time calculation means 11 Waveform storage unit 12 Zero cross position detection unit 13 Propagation time calculation unit 14 Review unit 102 Ultrasonic wave transmitter 103 Ultrasonic wave receiver 110 Timing control circuit

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G01H 5/00

Claims (3)

(57) [Claims] An ultrasonic transmitter and an ultrasonic receiver are provided, and a propagation time of an ultrasonic wave received by the ultrasonic receiver is calculated based on an output timing of the ultrasonic transmitter. A propagation time calculating means, the propagation time calculating means sequentially storing, at a predetermined timing, a waveform signal of the ultrasonic wave received by the ultrasonic wave receiver; and a waveform storage section for outputting the waveform signal. A zero-cross position detection unit that detects a zero-cross point based on waveform data; and a propagation time calculation unit that calculates a propagation time of a received ultrasonic wave based on an output of the zero-cross position detection unit and an output timing of the ultrasonic wave transmitter. In the ultrasonic wave transmitting and receiving apparatus having the above, the zero-cross position detecting unit detects the zero-cross point of the received waveform data based on the zero-cross point of the previously measured and specified waveform data. An ultrasonic transmission / reception device having a zero-cross point tracking function. 2. The zero-cross position detecting section reads the waveform data at the time corresponding to the previous zero-cross point and, when the waveform data is positive, determines the time at which the waveform data becomes zero at a time after the time. It has a zero-cross point tracking function that detects the zero-cross point by setting the zero-cross point as the zero-cross point, and setting the time when the waveform data becomes zero before the time when the waveform data is negative. The ultrasonic wave transmitting / receiving device according to claim 1, wherein 3. The apparatus according to claim 1, wherein said propagation time calculating means further comprises a zero-cross point review correction function for reviewing a zero-cross point by obtaining a correlation with reference waveform data. Ultrasonic wave receiver.