JP2993544B2 - Ultrasonic generator - 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 generator, and more particularly to an ultrasonic generator suitable for an ultrasonic nondestructive inspection apparatus using a pulse echo method such as an ultrasonic flaw detector and an ultrasonic densitometer. Related to the device.

[0002]

2. Description of the Related Art Conventionally, in an ultrasonic non-destructive inspection apparatus based on a pulse echo method using a pulsar, a high-voltage impulse voltage generated in the pulsar is applied to an ultrasonic transducer (hereinafter, abbreviated as “transducer” as appropriate). A vibration waveform determined by the frequency of the transducer has been propagated to the measured object. According to this method, the frequency of the transmitted ultrasonic wave is determined by the transducer, and when different frequencies are used, it is necessary to prepare a type of transducer corresponding to each frequency, which is inconvenient.

In order to solve such problems, recently,
The output of the sine wave oscillator 51 as shown in FIG. B. M (double balanced mixer) 52 and externally uses a switching signal (SW signal) as shown in FIG. B. The switching element constituting M52 is turned on / off (ON / OFF), and the transducer 53 is driven using a burst wave as shown in FIG. 3C.

[0004]

According to the above method using the apparatus shown in FIG. 2, the frequency of the ultrasonic wave output from the transducer 53 is determined by the frequency of the sine wave oscillator 51, and is within the operable frequency of the transducer 53. If the oscillation frequency of the sine wave oscillator 51 is swept,
The frequency can be changed without replacing the transducer 53, which is convenient for nondestructive inspection.

However, when the oscillation frequency of the sine wave oscillator 51 is as high as 5 to 20 MHz, D.I. B. M52
Even if the switching element constituting the device is turned off, the oscillation frequency component leaks slightly. Therefore, when the reception signal of the ultrasonic wave is very weak, the reception signal is erased by the leakage component, and the detection is performed. Has been found to be inconvenient.

[0006]

SUMMARY OF THE INVENTION It is an object of the present invention to improve the disadvantages of the prior art and to make it possible to measure the received signal with a high S / N ratio even when the received signal is very weak. An object of the present invention is to provide an ultrasonic generator.

[0007]

In order to achieve the above object, an ultrasonic generator according to the present invention comprises a pulse generator for continuously generating a pulse signal at predetermined time intervals, and a pulse generator from the pulse generator. A switching circuit that inputs a signal and turns on / off a pulse signal in accordance with the presence or absence of an external switching signal, and a transducer driving circuit that receives the pulse signal via the switching circuit and generates a burst wave for driving an ultrasonic transducer The transducer drive circuit comprises: an isolator for inputting a pulse signal via a switching circuit; and an input pulse from among the burst wave waveform data stored in a memory which receives a pulse signal output from the isolator and receives a pulse signal output from the isolator. Select the waveform data corresponding to the number and output it as a burst wave after analog conversion. A burst wave generating means, a power amplifier for amplifying the burst wave to a predetermined level, and a circuit opening / closing means which is turned on only when there is an output from the power amplifier and turned off otherwise, is provided. Have been.

[0008]

When transmitting an ultrasonic wave, a switching signal is input to the switching circuit, so that the continuous pulse signal generated by the pulse generator is turned on / off by the switching circuit and input to the isolator of the transducer driving circuit. The pulse signal output from the isolator is input to burst wave generating means, and the burst wave generating means selects waveform data corresponding to the number of input pulses from among burst wave waveform data stored in a memory in advance, and performs analog conversion. After that, it is output as a burst wave. This burst wave is amplified to an output required by the power amplifier, output to the ultrasonic transducer via the circuit opening / closing means, and the transducer is driven to output ultrasonic waves.

During reception of ultrasonic waves, if there is no pulse input to the isolator, the isolator disconnects the electrical connection between the transducer drive circuit and the logic units such as the pulse generator and the switching circuit at the preceding stage. In this case, since the burst wave generating means does not operate and there is no output from the power amplifier, the circuit opening / closing means is off.

[0010]

An embodiment of the present invention will be described below with reference to FIG.

FIG. 1 shows the configuration of an ultrasonic generator according to an embodiment of the present invention. In this embodiment, a pulse generator 1 that continuously generates a pulse signal at predetermined time intervals is used.
And an AND gate 2 as a switching circuit for inputting a pulse signal from the pulse generator 1 and turning on / off the pulse signal in accordance with the presence or absence of an external switching signal (SW signal), and via the AND gate 2 And a transducer driving circuit 3 for receiving a pulse signal from the pulse generator 1 and generating a burst wave for driving the ultrasonic transducer 4.

The AND gate 2 receives the pulse signal from the pulse generator 1 as one input and receives an external switching signal as the other input. While the switching signal is being input, the pulse from the pulse generator 1 is input. The signal is turned on / off and output to an isolator described later.

The transducer driving circuit 3 includes an isolator 5 for inputting a pulse signal through the AND gate 2.
And a pulse signal output from the isolator 5 and receive a ROM (Read Only) as a memory in advance.
The burst wave generating means 6 selects waveform data corresponding to the number of input pulses from the waveform data of the burst waves stored in the memory 11 and outputs it as a burst wave after analog conversion, and amplifies the burst wave to a predetermined level. It comprises a power amplifier 7 and a circuit opening / closing means 8 which is turned on only when there is an output from the power amplifier 7 and turned off in other cases.

More specifically, as the isolator 5, a photo isolator, a pulse transformer, or the like is used. The isolator 5 includes the transducer driving circuit 3 and the pulse generator 1 at the preceding stage when no pulse signal is input. Then, the electrical connection of the logic section such as the AND gate 2 is cut off.

The burst wave generating means 6 includes an isolator 5
The counter 10 counts the pulses output from the counter 10, and while detecting the pulse output from the isolator 5, the output of the reset (Reset) signal to the counter 10 is stopped and the pulse cannot be detected for a certain period of time. A pulse detector 9 for restarting the output of the reset signal to the counter 10 later, the ROM 11 for receiving the count value from the counter 10 and outputting the waveform data of the burst wave stored in advance according to the count value; This ROM
A D / A converter 12 for converting the waveform data output from the D / A converter 11 into an analog signal;
And an LPF (low-pass filter) 13 that smoothes the step-like analog signal output from the power amplifier 7 and outputs the same to the power amplifier 7 as a burst wave.

As shown in the figure, the circuit opening / closing means 8 is provided between the power amplifier 7 and the ultrasonic transducer 4 or a receiving section (not shown), and is connected in parallel with each other and in opposite directions. ₁ , D _2, and
These diodes D ₁ and D ₂ are turned on only when there is an output from the power amplifier 7.

Next, the operation of the embodiment constructed as described above will be briefly described.

At the time of transmitting an ultrasonic wave, a switching signal is input to the AND gate 2. Therefore, a continuous pulse signal generated by the pulse generator 1 is turned on and off by the AND gate 2 and input to the isolator 5 of the transducer driving circuit 3. I do. Since the pulse signal output from the isolator 5 is input to the counter 10 and the pulse detector 9, the pulse detector 9 stops outputting the reset signal to the counter 10. For this reason, the counter 10 starts counting the pulse signal. In this counting operation, the input of the switching signal is stopped, the AND gate 2 is turned off (OFF), and the pulse signal is sent to the counter 10 via the isolator 5. Continue until there is no more input. And this counter 10
Is input to the address of the ROM 11, and the data output from the ROM 11 corresponds to the count value (the number of input pulses) in the burst wave waveform data stored (written) in the ROM 11 in advance. Is output to the D / A converter 12. Then, a smoothed burst wave which is converted into an analog signal via the D / A converter 12 and the LPF 13 is outputted, and this burst wave is amplified to an output required by the power amplifier 17 and the circuit opening / closing means 8 is opened. Output to the ultrasonic transducer 4 via the The transducer 4 is driven by this burst wave, and outputs an ultrasonic wave.

As described above, the transmission of the ultrasonic wave ends,
When the pulse input to the isolator 5 is stopped, the electrical connection between the transducer driving circuit 3 and the logic units such as the pulse generator 1 and the AND gate 2 at the preceding stage is cut off by the isolator 5, so that the logic unit is disconnected. Noise is prevented from propagating inside the transducer drive circuit 3. Further, when a certain time has elapsed from the stop of the pulse input, the pulse detector 9 restarts outputting the reset signal to the counter 10, so that the counter 10 is reset.

At the time of receiving an ultrasonic wave, the effect of the isolator 5 is to prevent the noise of the logic section such as the pulse generator 1 and the AND gate 2 from being propagated inside the transducer drive circuit 3 as in the above. Yes, and
In this case, since there is no output from the power amplifier 7, the diodes D ₁ and D ₂ constituting the circuit opening / closing means 8 are off, and the signal received from the transducer 4 is
To prevent the air from flowing into
Further, it is possible to prevent the white noise generated from the power amplifier 7 from propagating to the receiving unit and lowering the S / N ratio of the receiving unit.

As described above, according to the present embodiment,
At the time of receiving ultrasonic waves, the burst wave generating means 6 does not operate and there is no output from the power amplifier 7, so that the circuit opening / closing means 8 is off, and the frequency component of the burst wave is leaked and the reception S
Since the frequency of the continuous pulse output from the pulse generator 1 is very different from the frequency of the burst wave without lowering the / N ratio, the frequency component of the continuous pulse from the pulse generator 1 during reception of the ultrasonic wave Even if it leaks, it is quite different from the receiving frequency, and can be easily removed by inserting an LPF into the receiving unit. The noise leakage from the pulse generator 1 is inserted into only one noise propagation path. In addition, there is no generation of logic noise from the burst wave generating means 6 unless the burst wave generating means 6 operates. On the other hand, when the burst wave generating means 6 operates and the logic noise is generated from this part during transmission, a little noise does not matter, and this noise can be removed by the LPF 13. Therefore, the noise can be suppressed to a very low level, and even when the received signal is very weak, such as when a non-destructive inspection is performed on an object to be measured having a very large propagation loss, a high S / N ratio is obtained. This makes it possible to measure the received signal.

Also, by making the output frequency of the pulse generator 1 variable, the frequency of the burst wave can be made variable, and the configuration can be made easier than when the sine wave oscillator is made variable.

[0023]

As described above, according to the present invention,
At the time of receiving ultrasonic waves, since the burst wave generating means does not operate and there is no output from the power amplifier, the circuit opening / closing means is off, and the frequency component of the burst wave leaks to lower the S / N ratio of reception. Since the frequency of the continuous pulse output from the pulse generator and the frequency of the burst wave are very different, even if the frequency component of the continuous pulse from the pulse generator leaks, it is quite different from the reception frequency. L in part
It can be easily removed by inserting a PF or the like, and noise leakage from the pulse generator can be greatly attenuated by the action of the isolator. The generation of logic noise from the generation means is also small. Therefore, the noise can be suppressed to a very low level, and even when the received signal is very weak, such as when performing a nondestructive inspection of a measured object having a very large propagation loss, a high S / N ratio is obtained. Thus, there is an unprecedented excellent effect of enabling the measurement of the received signal.

[Brief description of the drawings]

FIG. 1 is a block diagram showing the configuration of an embodiment of the present invention.

FIG. 2 is a block diagram showing a configuration of a conventional example.

FIG. 3 is a diagram for explaining the operation of FIG. 2;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Pulse generator 2 AND gate as a switching circuit 3 Transducer drive circuit 4 Ultrasonic transducer 5 Isolator 6 Burst wave generation means 7 Power amplifier 8 Circuit switching means 11 ROM as memory

Claims (1)

(57) [Claims] 1. A pulse generator for continuously generating a pulse signal at predetermined time intervals, a pulse signal from the pulse generator being input, and turning on / off the pulse signal in accordance with the presence or absence of an external switching signal. A switching circuit that turns off, and a transducer driving circuit that receives the pulse signal through the switching circuit and generates a burst wave for driving an ultrasonic transducer, and the transducer driving circuit is configured to control the pulse through the switching circuit. An isolator for inputting a signal and a pulse signal output from this isolator are input, and waveform data corresponding to the number of input pulses is selected from among the waveform data of the burst waves stored in the memory in advance, and is used as a burst wave after analog conversion. A burst wave generating means for outputting, and the burst wave to a predetermined level. An ultrasonic wave generator comprising: a power amplifier that amplifies the power by a power amplifier; and circuit opening / closing means that is turned on only when there is an output from the power amplifier and turned off in other cases.