JPS6336474B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an ultrasonic pulse transmission/reception system for ultrasonic flowmeters, ultrasonic level meters, and the like.

Generally, an ultrasonic transmitter excites the transmitter with a waveform shown in Figure 1 a or b at every time interval determined by a signal from a time base, and emits ultrasonic pulses from this transmitter. However, the ultrasonic reception signal received by the receiver via the propagation medium of the ultrasonic pulse has a waveform shown by the solid line in FIG. 2. In order to stably measure the ultrasonic propagation time in this case, for the received wave with the waveform shown in Figure 2,
A wave that can be triggered as stably as possible, that is, a vibration wave with an amplitude difference between the previous and succeeding vibration waves, is used as a trigger wave (generally, when the vibration wave of the received wave exceeds a predetermined level, it is determined that the received wave has arrived) It is best to use the vibration wave as a trigger wave in the measurement method.

Therefore, in FIG. 2, a reference level V'r is provided and, for example, the vibration wave _a2 is used as a trigger wave. When detecting a trigger wave using this method, if the received wave changes as shown by the dashed line or dashed line in Figure 2, the trigger wave is immediately changed to a vibration wave in the former case.
In _{the latter} case, the vibration wave changes to a ₃ , which poses a measurement problem. Such fluctuations in received waves frequently occur when the propagation medium contains bubbles, foreign matter, etc. In such cases, there have conventionally been two methods for controlling fluctuations in the received waves using AGC. One is to focus on a specific trigger wave among the received waves and keep the amplitude of that wave at a constant level.
This is a method of applying AGC (hereinafter, the wave in this case is
(referred to as AGC focus wave). In this method, if the received wave as shown by the solid line in Figure 2 changes faster than the AGC tracking as shown by the dashed-dotted line or broken line, not only the trigger wave but also the AGC target wave will change, and the source shown by the solid line will change. The trigger wave and AGC wave no longer return to the current wave. Another method is to focus on the peak of the received wave and apply AGC. However, in this case, the trigger wave and the AGC target wave generally do not match, and there is a time lag, so AGC is often not applied to the trigger wave as effectively as planned. This is because if bubbles or foreign matter are mixed into the propagation medium, the envelope of the received wave changes as shown by the solid line in FIG. 2 or the wave shown by the broken line or the dashed line. Therefore, the trigger wave inevitably becomes unstable. Furthermore, in order to improve this point, if there is a change in the received wave as shown by the solid line, dashed line, or broken line in Figure 2, the reference level V'r is set to Vr, so that the oscillating wave a ₃ as a trigger wave has been devised, but it cannot be said that the above-mentioned problems have been fundamentally solved. In addition, if you try to apply AGC to the peak of the received wave and use that peak wave as the trigger wave in order to compensate for the drawbacks of the two methods of stabilizing the trigger wave using AGC, as shown in Figure 2, which vibration wave In many cases, it is not clear whether a wave is a peak wave or not, making it difficult to implement this method. Therefore, a skilled engineer is required to adjust and set up the ultrasonic transmitter/receiver with the problems described above on-site, and it is not something that anyone can easily set up.

The present invention was made to solve the above-mentioned problems, and as shown in Fig. 2, the vibration wave number is extremely small compared to the conventional ultrasonic reception wave, and the envelope of the reception wave has a small rise. It is an object of the present invention to provide an ultrasonic transmitting/receiving method and apparatus that can always obtain a steep received waveform as shown in FIG.

Therefore, in order to obtain the received wave as shown in Figure 3,
The received wave as shown in Fig. 3 can be obtained as a received signal by the function of monitoring the waveform being received and the function of correcting the waveform that fluctuates as shown by the broken line or the dashed-dotted line in Fig. 2. There is. The received wave obtained in this way as shown in Fig. 3 makes it possible to make the AGC target wave and the trigger wave the same peak wave as described later, and eliminates air bubbles, foreign objects, and obstructions in the propagation path. Ultrasonic propagation time can be measured accurately and stably even in cases where ultrasonic waves are included, and furthermore, anyone can easily and accurately adjust the ultrasonic propagation time.

Next, the present invention will be described with reference to an illustrated embodiment. FIG. 4 is a block diagram showing the circuit configuration of the present invention. The present invention is composed of a transmitter 1 and a receiver 2, and a transmission signal from the transmitter 1 is supplied to the wave transmitter.
The signal received by the receiver is then transmitted to the receiver 2.
The received waveform is monitored, and the waveform is modified so that the received wave as shown in FIG. 3 can be received.

FIG. 5 is an explanatory diagram of the operation of each configuration in FIG. 4,
The configuration and operation of the present invention will be explained below using these figures. A transmission signal from the transmitter 1 is supplied to the transmitter, and an ultrasonic pulse is emitted. In this case, the transmission signal used is a pulse signal as shown in FIG. 1a or b, or a signal consisting of n pulse trains as shown in FIG. 5 obtained as described below. Now, the transmission frequency adjustment circuit 3 in the transmitter 1 transmits an output signal as shown in FIG. 5 at a transmission frequency that almost matches the natural frequency of the transmitter oscillated by the oscillator included therein. The signal is supplied to the waveforming circuit 4, and based on the transmission command, is converted by the transmission waveforming circuit into a signal consisting of a train of N pulses as shown in Fig. 5. waveform), is amplified by the transmission amplifier 5 and supplied to the transmitter.

The signal received by the receiver is then transmitted to the receiver 2
The signal is amplified by the amplifier 6-1, the reception polarity switching circuit 13, and the amplifier 6-2 to obtain a reception signal as shown in FIG. This received signal is simultaneously applied to three types of level comparators. As the output of the peak level comparator 7 having the highest reference level, a peak pulse as shown in FIG. 5 is sent to the rise ratio detection circuit 10 through the AGC circuit 8 and the peak position storage circuit 9. Among these, the AGC circuit 8 controls the gain of the receiver by the peak pulse sent to the AGC circuit 8, and operates so that the peak of the received signal matches the first reference level Vp. The peak and the first reference level Vp are almost in agreement.

On the other hand, the output of the zero select comparator 11 having the third reference level Vzs is at the second reference level.
Zero cross comparator 1 with Vz (approximately OV)
The zero cross comparator 12 operates only when the output of the zero select comparator 11 is obtained, and outputs a zero cross pulse as shown by the solid line in FIG. Therefore, the rise ratio detection circuit 10 monitors the amplitude ratio between the peak wave of the received signal and the vibration waves before and after it by comparing the arrival time of the pulse obtained by passing through the peak position storage circuit 9 and the zero-crossing pulse. are doing. When the received signal is as shown by the solid line in FIG. 5, there is no wave other than the peak wave that exceeds the third reference level Vzs, so only one zero-cross pulse is output at a position after the peak wave as shown by the solid line. Therefore, in this case, the peak pulse always reaches the rise ratio detection circuit 10 earlier. By determining the arrival of the received wave at the rise of the zero-crossing pulse in such a state, even if the propagation path of the ultrasonic pulse contains air bubbles or foreign matter, Therefore, the ultrasonic propagation time can be measured accurately and stably.

Furthermore, in the case where the received signal in FIG. 4 is as shown by the broken line in FIG. In addition to the peak wave, there are also vibration waves before it. Therefore, a plurality of zero-crossing pulses are outputted as shown by the broken line in FIG. 5, and reach the rising ratio detection circuit 10 earlier than the peak pulse. Therefore, by comparing the arrival times of the peak pulse and the zero-crossing pulse, the equivalent rise ratio of the peak wave and the preceding and succeeding vibration waves in such a received signal is determined by the first and third reference level difference (Vp- Vzs)
You can check whether there are any.

Furthermore, if the received wave shown by the solid line in FIG. 6 is attenuated by bubbles or foreign matter in the propagation medium, only that attenuation is compensated by the AGC circuit 8, and the received signal obtained by the AGC circuit 8 is as shown in the figure. The waveform may be as shown by the broken line.

Regarding such a received signal waveform, the above-described rise ratio detection circuit 10 checks the amplitude difference between the peak wave and the vibration waves before and after it, equivalently detects the rise ratio, and calculates the amplitude of the peak wave and the vibration waves before and after it. If the difference is smaller than the difference between the first and third reference levels described above, the rise ratio detection circuit 10 outputs an "abnormal signal" indicating that the received signal is abnormal. This signal is supplied to the reception polarity switching circuit 13. This reception polarity switching circuit 13 is connected to the rising ratio detection circuit 10.
When receiving an "abnormal signal" from the receiver, the amplification polarity of the receiver is switched, and at that point the received signal is inverted and supplied to each of the comparators via the amplifier 6-2. This is apparently equivalent to changing the first reference level Vp and the third reference level Vzs to the negative side as indicated by the broken lines in FIG. 6.
In this case, as shown by the broken line in the same figure, the equivalent rise ratio between the peak wave of the received signal and the oscillation waves before and after it becomes more than (Vp - Vzs), and as a result, the rise ratio detection circuit 10 determines that the received signal is normal and stops outputting the "abnormal signal". In this way, it is possible to obtain a trigger wave that allows accurate and stable determination of the arrival time of the ultrasonic reception wave. Further, by obtaining a signal indicating that the reception polarity has been reversed, correction can be performed by a separately prepared processing circuit 14 for the time t in FIG. 6, corresponding to the change in the trigger wave.

Furthermore, if the fluctuation of the received wave becomes faster than the tracking of the AGC circuit 8, the reference level Vp
Vibration waves exceeding 1000 yen may occur in addition to the peak waves. Even in this case, the rise ratio detection circuit 1
The peak position storage circuit 9 shown in FIG. 4 is used so that a correct judgment can be made based on 0. This circuit is a circuit for storing the arrival time of the peak pulse shown in FIG. 5, and the means for storing it can be arbitrarily obtained, such as converting it into a voltage and holding it. This circuit is designed to follow the peak pulse with a certain time constant, so it does not follow instantaneous fluctuations, and even in the transient state of AGC operation for the received signal as shown in Figure 7, it does not follow the peak pulse. The peak of can be sent to the rise ratio detection circuit 10.

By doing so, as described above, a received wave as shown in FIG. 3 is obtained in which the vibration wave number is extremely small and the envelope of the received wave has a steep rise, and accurate and stable measurement can be performed.

On the other hand, for example, as shown by the dashed line in FIG. 8, an equivalent rise ratio of (Vp-Vzs) may not be obtained on either the positive side or the negative side of the received signal. At this time, even if the reception polarity of the reception polarity switching circuit 13 is switched, a stable peak wave cannot be expected. In such a case, the rise ratio detection circuit 10 sends the above-mentioned "abnormal signal" to the transmission frequency adjustment circuit 3 of the transmitter 1, and the transmission frequency adjustment circuit 3 that receives this signal changes the transmission frequency little by little. Go. In this way, by changing the transmission frequency using the signal from the rise ratio detection circuit 10, the received signal shown by the dashed line in FIG. 8 can be restored as shown by the solid line, and stable measurement can be maintained. Can be done. In this way, a more effective method of transmitting and receiving ultrasonic pulses can be obtained by modifying the received signal waveform using the receiving polarity switching means and adding a transmitting frequency adjustment means to make this modification function more effective. can get.

In the above-described embodiment, two reference levels were used to detect the rise ratio, but other methods, such as differentiating the envelope of the received signal, are also possible.

Furthermore, by using a transmission signal ' consisting of N pulse trains and one pulse of opposite phase as the transmission wave, the rise of the envelope of the reception wave becomes even steeper, and more effects can be obtained.

[Brief explanation of the drawing]

Figure 1 is a waveform diagram of a transmitted pulse, Figure 2 is a waveform diagram of a received signal due to an ultrasonic pulse, Figure 3 is a waveform diagram of a received signal obtained by the present invention, and Figure 4 shows the circuit configuration of the present invention. Block diagram, Figures 5 to 4 are waveform diagrams to explain the operation of Figure 4, Figure 6 is a diagram of the received waveform attenuated by bubbles and foreign objects in the propagation medium, and Figure 7 is the received waveform. FIG. 8 is a diagram showing a case where the fluctuation becomes faster than the tracking of the AGC circuit, and FIG. 8 is a diagram showing a case where the rise ratio of the envelope of the received wave is small. 3... Transmission frequency adjustment circuit, 4... Transmission wave forming circuit, 7... Peak level comparator, 10...
... Rise ratio detection circuit, 11 ... Zero cross select comparator, 12 ... Zero cross comparator, 13 ... Reception polarity switching circuit.

Claims (1)

[Claims] 1. Ultrasonic pulses are emitted from an ultrasonic transmitter and the peak wave of the vibration waves of the ultrasonic reception signal received via the propagation medium is set so that the peak of the wave coincides with the first reference level. In an ultrasonic measurement method, the reception amplification degree is controlled as follows, and the time point at which the peak wave crosses a third reference level is determined as the arrival time of the ultrasonic reception wave, and the propagation time from the time of transmission of the ultrasonic pulse is detected, When the amplitude difference between the peak wave and the vibration waves before and after the peak wave is equal to or less than the level difference between the first reference level and a second reference level between the first and third reference levels, an abnormality signal is generated; An ultrasonic transmitting/receiving method characterized in that the reception amplification polarity is switched using the signal to invert the phase of the ultrasonic reception signal to obtain an ultrasonic reception signal in which the amplitude difference is equal to or greater than the level difference. 2. The ultrasonic transmission/reception method according to claim 1, wherein the ultrasonic pulse consists of n pulse trains. 3 An ultrasonic pulse consisting of n pulse trains is emitted from an ultrasonic transmitter, and the peak of the vibration wave of the ultrasonic reception signal received via the propagation medium is set so that the peak of the wave coincides with the first reference level. In an ultrasonic measurement method, the reception amplification degree is controlled as follows, and the time point at which the peak wave crosses a third reference level is determined as the arrival time of the ultrasonic reception wave, and the propagation time from the time of transmission of the ultrasonic pulse is detected, When the amplitude difference between the peak wave and the vibration waves before and after the peak wave is less than or equal to the level difference between the first reference level and a second reference level between the first and third reference levels, an abnormality signal is generated. The reception amplification polarity is switched by the signal, and the period of the pulse train of the ultrasonic pulse is changed by the abnormal signal, and the ultrasonic reception signal is obtained such that the amplitude difference between the peak wave and the vibration waves before and after the peak wave is equal to or greater than the level difference. An ultrasonic transmitting and receiving method characterized by: 4 An ultrasonic pulse consisting of n pulse trains is emitted from an ultrasonic transmitter, and the peak of the vibration wave of the ultrasonic reception signal received via the propagation medium is set so that the peak of the wave coincides with the first reference level. In an ultrasonic measurement method, the reception amplification degree is controlled as follows, and the time point at which the peak wave crosses a third reference level is determined as the arrival time of the ultrasonic reception wave, and the propagation time from the time of transmission of the ultrasonic pulse is detected, When the amplitude difference between the peak wave and the vibration waves before and after the peak wave is less than or equal to the level difference between the first reference level and a second reference level between the first and third reference levels, an abnormality signal is generated. The ultrasonic wave receiving signal is characterized in that the period of the pulse train of the ultrasonic pulse is changed by the abnormal signal, and an ultrasonic reception signal in which the amplitude difference between the peak wave and the vibration waves before and after the peak wave is equal to or greater than the level difference is obtained. Method of transmitting and receiving sound waves. 5. Emit an ultrasonic pulse consisting of n pulse trains, and adjust the reception amplification so that the peak of the peak wave of the vibration waves of the ultrasonic reception signal received via the propagation medium matches the first reference level. In an ultrasonic measurement device that detects the propagation time from the time of transmission of the ultrasonic pulse by controlling the time point at which the peak wave crosses another reference level as the arrival time of the received ultrasonic wave, the received signal and the first a peak level comparator that outputs a peak pulse when compared with a reference level of the first reference level; a zero cross comparator that outputs a zero cross pulse when the first reference level is crossed; A zero cross select comparator that controls the operation compares the arrival times of the peak pulse and the zero cross pulse, and when one zero cross pulse arrives after the peak pulse arrives, it is considered normal and otherwise outputs an abnormal signal. A receiver comprising a rise ratio detection circuit and a receiving polarity switching circuit for switching the polarity of a receiving amplifier according to the abnormal signal, and a receiver that changes the oscillation frequency in response to the abnormal signal and changes the period of the n pulse trains to exceed An ultrasonic transceiver device consisting of a transmitter that outputs sonic pulses.