JP2001330500A - Interface measuring device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To detect the interface between a liquid and foreign matter while avoiding the effects of floating sludge by a simple and inexpensive constitution. SOLUTION: It is impossible to detect the interface 5 through the use of one ultrasonic oscillator when there is the floating sludge 2a, etc., in a refection path from the foreign matter such as sludge 2, etc. A plurality of ultrasonic oscillators (ultrasonic transmitters/receivers 81-85) are used to transmit ultrasonic waves via a timing circuit 11, drive circuit 12, etc. By receiving and processing the reflected waves from the interface 5 at a signal processing part 15 via a clamp circuit 13 and amplifier 14, it is possible to receive the reflected waves also from the passes which do not pass through the floating sludge 2a to improve accuracy.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sedimentation tank for drainage treatment, sewage treatment and the like, and an interface measuring device for measuring an interface with a foreign substance which forms an interface in a liquid and precipitates.

[0002]

2. Description of the Related Art In order to purify a liquid containing sludge, for example, as shown in FIG. 8, a liquid containing sludge is separated into a sludge 2 and a supernatant liquid 3 in a sludge treatment tank 1, and then the precipitated sludge 2 is removed. Processing tank 1
Is discharged from the lower part of the container for processing. In this case, in order to know an appropriate settling sludge discharge time,
From the depth H1 to the interface 5 between the supernatant 3 and the settled sludge 2,
Alternatively, it is necessary to know the depth H2 from the interface 5 to the tank bottom 1a. Therefore, a method using an ultrasonic wave is widely used as a means.

For example, a wave transmitting / receiving surface is immersed in a liquid in the vicinity of a liquid surface 4, and an ultrasonic transmitter 6 and an ultrasonic receiver 7 are provided (or a transmitting / receiving vibrator is provided), and a timing circuit 11 is provided.
The driving pulse (driving timing signal D) is applied to the ultrasonic transmitter 6 through the driving circuit 12 to transmit the ultrasonic wave S toward the tank bottom 1a. Then, the reflected wave B from the interface 5 and the tank bottom 1a is received, amplified by the amplifier circuit 14, and subjected to predetermined signal processing by the signal processing unit 15, and the intensity of the received signal is displayed on the screen of the display circuit 16 (display). (Device) 17. With this display, the position of the interface or the bottom of the tank can be visually determined. Further, the interface can be detected by executing a determination algorithm in the signal processing unit 15 for recognizing a position where there is a change in reception intensity as an interface, instead of performing a visual determination. Based on the detected interface information, the discharge valve provided at the lower part of the sludge treatment tank is opened to automatically discharge the accumulated sludge.

[0004]

In the sludge purification tank, the sludge settles at the upper part of the interface in the form of suspended sludge (see reference numeral 2a in FIG. 8) until it is deposited. The ultrasonic wave transmitted to measure the interface is also reflected from the sludge and returns to the ultrasonic receiver. Since this reflected wave becomes noise for reflection from the interface, there is a problem that the interface cannot be detected accurately. Further, since the ultrasonic waves are diffused according to the directivity, the sound pressure is attenuated farther away.
Therefore, it is difficult to reliably receive a reflected wave from an interface located far away. In general, to increase the reception strength, it is sufficient to increase the transmission power, but in that case, there arises a problem that the power supply circuit must be increased. Therefore, an object of the present invention is to make it possible to avoid the influence of suspended sludge with a simple and inexpensive configuration.

[0005]

In order to solve such a problem, according to the first aspect of the present invention, in order to measure an interface with a foreign substance which forms an interface in a liquid and precipitates, the liquid in the vicinity of the liquid surface is measured. In an interface measuring apparatus for emitting an ultrasonic pulse from an ultrasonic transmitter to an interface and receiving the reflected pulse by an ultrasonic receiver and measuring the interface based on the received signal, the ultrasonic transmitter and the ultrasonic receiver A plurality of devices are provided, and the transmission timing is determined based on the relative installation position, the sound speed of the medium, and the depth of focus so that the ultrasonic pulse from each ultrasonic transmitter simultaneously arrives at a predetermined position, and is transmitted. It is characterized by the following. According to the first aspect of the present invention, the transmission direction of the ultrasonic transmitter can be directed to a direction in which a sound wave is focused (the invention of the second aspect), or the ultrasonic transmitter and the ultrasonic receiver can be connected to each other. A timing circuit for generating an ultrasonic pulse transmission timing signal for the plurality of ultrasonic transmitters, and receiving each of the ultrasonic transmitters by receiving the timing signal. It is possible to provide a drive circuit for sequentially driving and a signal processing unit for simultaneously receiving outputs from the respective ultrasonic receivers and performing predetermined processing (invention of claim 4).

In the above invention, the signal processing unit may include a plurality of delay circuits for delaying the outputs from the respective ultrasonic receivers, and an adder circuit for adding the outputs of the respective delay circuits. Alternatively, the signal processing section stores a plurality of AD converters for converting outputs from the respective ultrasonic receivers into digital data, and stores digital data from the respective AD converters. And an arithmetic circuit for performing a predetermined operation based on output data from the memory (the invention according to claim 6). According to the sixth aspect of the present invention, the memory stores the digital data from the respective AD converters with a delay therebetween, and the arithmetic circuit can sequentially add the output data from the memory. Invention),
Alternatively, digital data from each AD converter is stored in the memory, and the arithmetic circuit can delay and add output data from the memory to each other (the invention of claim 8).

According to the first aspect of the present invention, a timing circuit for generating a transmission timing signal of an ultrasonic pulse to the plurality of ultrasonic transmitters, and sequentially driving each ultrasonic transmitter in response to the timing signal A driving circuit,
A selection circuit for sequentially selecting the output from each of the ultrasonic receivers and a signal processing unit for receiving the output from the selection circuit and performing a predetermined process can be provided (the invention of claim 9). In the invention of Item 9, the signal processing unit includes a plurality of A / D converters for converting outputs from the respective ultrasonic receivers into digital data, a memory for storing digital data from the respective A / D converters, An arithmetic circuit for performing a predetermined operation based on output data from the memory (the tenth aspect of the present invention). In the tenth aspect, the memory stores digital data from each AD converter. And the arithmetic circuit can add the output data from the memory while delaying each other (the invention of claim 11).

[0008]

FIG. 1 is a configuration diagram showing a first embodiment of the present invention. The difference between the conventional example shown in FIGS. 1 and 8 is that a plurality of transducers are provided (the ultrasonic transceiver 8).
1 to 85), whereby the number of drive circuits 12 and the number of amplifier circuits 14 are increased, and the timing circuit 11 for controlling these circuits is changed to output each timing signal. Also, since FIG. 1 shows an example in which the transmission and reception elements are used as the same,
The clamp circuit 13 is provided so that a transmission signal having a large amplitude is not supplied to the amplifier circuit 14. Therefore, if the transmitter and the receiver are separated, the clamp circuit 13 is unnecessary.

The drive timing will be described with reference to FIGS. FIG. 2 shows an example in which sound waves transmitted from a plurality of ultrasonic transducers (ultrasonic transceivers 81 to 85) are converged according to three levels of depth. The number of convergence steps is determined by a convergence area determined by the ultrasonic frequency to be used, the directivity of the transducer, and the like. In addition, the ultrasonic transducers arranged on both sides are devised toward the center so that the sound waves are easily converged at the center. This angle is desirably directed near the central depth so that the sound pressure is improved over the entire area where the interface is searched. Further, it is needless to say that it is ideal to make the direction of the ultrasonic transducer movable according to the focal position to be converged.

As shown in FIG. 2, the three steps are defined as near, middle, and far areas, and the center points in the respective areas are defined as Cn, Cm, and Cf, respectively. then,
The drive timing applied to the ultrasonic vibrator differs for each region, and consideration is given to the sound waves reaching the centers Cn, Cm, and Cf of the respective regions simultaneously. Therefore, it is not possible to focus on multiple areas at the same time,
The ultrasound is converged and transmitted for the number of times divided into regions. In general, the moving speed of the sludge interface and suspended sludge is sufficiently slower than the ultrasonic wave propagation speed and the operation cycle of the entire system related to the received signal processing. However, no particular problem arises.

A method for obtaining the drive timing in a certain area will be described with reference to FIG. (A) so that sound waves from the transducers reach the focal point C at the same time.
The distance difference between L1 and L5 is adjusted based on the relative positional relationship between the transducers. For this purpose, the drive timing is shifted by, for example, the time obtained by dividing the distance differences L1 to L5 by the sound speed v, and the driving timing is shifted as shown in FIG.
When the ultrasonic transceiver 83 is used as a reference as shown in (f), 81, 82, 84, 85, etc. are advanced by the drive timing (L1 / v, L2 / v, L4 / v, L5 / v). To be transmitted. The shift amount of the drive timing depends on the depth of focus and the speed of sound in addition to the relative positional relationship between the transducers.

The signal processing unit 15 for the received signal with respect to the transmitted sound wave shown in FIG. 1 assumes that the reflection source of the reception signal is at the focal position at the time of transmission and has a time difference corresponding to the difference in the distance from the reflection source to each transducer. Add to each other. As a method of processing the received signal, a delay synthesizing method using a delay circuit 151 and an adding circuit 152 as shown in FIG. 4 or a receiving waveform from each transducer as shown in FIG.
There is a method in which the data is individually converted into digital data by the converter 154, stored in the memory 155, and the output is read out and added to each other by the arithmetic unit 156. As described above, in any method, the time to be shifted is determined by the depth of focus and the speed of sound in addition to the relative positional relationship of the transducers. In the method of FIG. 5 for performing AD conversion,
This can be realized by any method such as shifting storage areas from one another when data is taken into the memory to facilitate subsequent processing, or considering the amount of shift at the time of addition after taking into the memory.

FIG. 6 is a block diagram showing a second embodiment of the present invention. Focusing on the fact that the operating speed of the sludge interface and suspended sludge is very slow compared to the propagation speed of ultrasonic waves, and the period required for transmission and reception is fast, it is not possible to receive signals from multiple transducers simultaneously. Instead, the switching circuit (selection circuit) 18 sequentially selects and receives the signals one by one, and reproduces the received waveform from the received signals corresponding to the transmitted sound waves for the number of transducers. The method of reproducing the received waveform is the same as in FIG.
After D-converted into digital data, the data is added with the time difference shifted. By doing so, the receiving circuit can be integrated into one system, and the circuit configuration can be simplified.

FIG. 7 shows a processing flow in the case of FIG. Here, an example is shown in which three focus areas are used and five vibrators (i = 5) are used. First, for the area of naer, the signal is transmitted so as to converge to the focal position of Cn (see), and a received signal as a reflected wave is received by the first transducer (see,). Next, a reception signal is acquired while switching the vibrator in order from the second to the fifth at the same transmission timing (see,). The five data of the naer area are added to each other in consideration of the time difference corresponding to the distance difference between each transducer position and the focus position (
reference). This operation is similarly performed for the middle area and the far area, and finally, data of the entire area is obtained (see,). Based on the data of all the regions obtained in this way, the intensity of the received signal is displayed on the display device 17 such as a CRT or the like, and the operation for estimating the position of the interface is executed to control the emission, as in the past. Or

[0015]

According to the present invention, a single vibrator is affected by suspended sludge on the ultrasonic wave propagation path. However, according to the present invention, a path of sound waves by a plurality of ultrasonic vibrators can be used. In addition, it is possible to avoid a path including the position of suspended sludge, thereby providing an advantage that highly reliable measurement can be performed. Further, since the transmission timings of the plurality of vibrators are shifted in accordance with the installation positions, it is not necessary to transmit at the same time. As a result, the sound pressure can be improved at the target interface search depth without increasing the power supply circuit capacity. Furthermore, if a plurality of reception signals are sequentially switched instead of being received simultaneously, a single reception circuit system can be used, and an increase in circuit scale can be prevented.

[Brief description of the drawings]

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

FIG. 2 is an explanatory diagram of a sound beam in FIG.

FIG. 3 is a diagram illustrating a relative installation position and driving timing of the ultrasonic transducer in FIG. 1;

FIG. 4 is an explanatory diagram of a received signal processing method in FIG. 1;

FIG. 5 is an explanatory diagram of another reception signal processing method in FIG. 1;

FIG. 6 is a configuration diagram showing a second embodiment of the present invention.

FIG. 7 is a flowchart illustrating a signal processing operation in FIG. 6;

FIG. 8 is a configuration diagram showing a conventional example.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Sludge treatment tank, 2 ... Settled sludge, 3 ... Supernatant, 4 ... Liquid surface, 5 ... Interface, 6 ... Ultrasonic transmitter, 7 ... Ultrasonic receiver,
81 to 85: ultrasonic transceiver, 11: timing circuit,
Reference numeral 12: drive circuit, 13: clamp circuit, 14: amplifier circuit, 15: signal processing unit, 16: display circuit, 17: display device, 18: switching circuit (selection circuit), 151: delay circuit,
152 ... addition circuit, 153 ... signal processing circuit, 154 ... A
D converter, 155 ... memory, 156 ... operation circuit.

Claims (11)

[Claims] An ultrasonic transmitter emits an ultrasonic pulse from the liquid near the liquid surface to the interface and measures the reflected pulse to measure an interface with a foreign substance that forms an interface and precipitates in the liquid. An interface measuring device that receives an ultrasonic wave and measures an interface based on the received signal, wherein a plurality of ultrasonic transmitters and ultrasonic receivers are provided, and an ultrasonic pulse from each ultrasonic transmitter is predetermined. An interface measuring apparatus characterized in that a transmission timing is determined based on a relative installation position, a sound speed of a medium, and a depth of focus so as to arrive at a position at the same time, and transmission is performed. 2. The interface measuring apparatus according to claim 1, wherein a transmission direction of the ultrasonic transmitter is directed to a direction in which a sound wave is focused. 3. The interface measuring apparatus according to claim 1, wherein the ultrasonic transmitter and the ultrasonic receiver are shared. 4. A timing circuit for generating a transmission timing signal of an ultrasonic pulse to the plurality of ultrasonic transmitters, a driving circuit for receiving the timing signal and sequentially driving each ultrasonic transmitter, The interface measuring apparatus according to claim 1, further comprising: a signal processing unit that receives an output from the acoustic wave receiver at the same time and performs a predetermined process. 5. The signal processing unit according to claim 4, further comprising: a plurality of delay circuits for delaying outputs from the respective ultrasonic receivers; and an adding circuit for adding outputs of the respective delay circuits. 2. The interface measuring device according to item 1. 6. A signal processing unit comprising: a plurality of A / D converters for respectively converting outputs from the respective ultrasonic receivers into digital data; a memory for storing digital data from the respective A / D converters; 5. An interface measuring apparatus according to claim 4, further comprising an arithmetic circuit for performing a predetermined operation based on the output data of the interface. 7. The memory according to claim 6, wherein the memory stores the digital data from each AD converter with a delay with respect to each other, and the arithmetic circuit sequentially adds the output data from the memory. Interface measurement device. 8. The interface according to claim 6, wherein the memory stores digital data from each AD converter, and the arithmetic circuit delays and adds output data from the memories to each other. measuring device. 9. A timing circuit for generating a transmission timing signal of an ultrasonic pulse to the plurality of ultrasonic transmitters, a driving circuit for receiving the timing signal and sequentially driving each ultrasonic transmitter, 2. The interface measuring apparatus according to claim 1, further comprising a selection circuit for sequentially selecting an output from the acoustic wave receiver, and a signal processing unit for receiving the output from the selection circuit and performing a predetermined process. 10. A signal processing unit comprising: a plurality of A / D converters for converting outputs from the respective ultrasonic receivers into digital data; a memory for storing digital data from the respective A / D converters; 10. An interface measuring apparatus according to claim 9, further comprising an arithmetic circuit for performing a predetermined operation based on the output data of the interface. 11. The memory according to claim 10, wherein the memory stores digital data from each AD converter, and the arithmetic circuit delays and adds output data from the memories to each other. Interface measurement device.