JP5935451B2 - Interface level meter - Google Patents

Description

  The present invention relates to an interface level meter for measuring the position of an interface between a suspended sediment layer in water and its supernatant.

  Generally, a wastewater treatment facility or a sewage treatment facility in a factory is provided with a sedimentation tank (or a sedimentation basin) for solid-liquid separation of sludge and its supernatant water by sedimentation of wastewater (sewage). In order to monitor the amount of sludge accumulated in the settling tank, for example, an ultrasonic sensor is used to transmit ultrasonic waves toward the bottom of the settling tank, and the reflected wave reception timing and received intensity are analyzed, and sludge and supernatant water are analyzed. Detection of the position (depth) of the interface with (see, for example, Patent Document 1). The interface position can be obtained from the reception timing (propagation time) of the reflected wave whose reflection intensity is equal to or greater than a predetermined threshold value.

  However, in such a method for detecting the interface position, when there is a foreign substance such as a bubble, suspended sludge, or pipe on the ultrasonic wave propagation path between the ultrasonic sensor and the interface, the intensity of the reflected wave from the foreign substance There is a problem that the position of the interface cannot be accurately detected.

JP 2011-13084 A

  An object of this invention is to provide the interface level meter which can detect the position of the interface of sludge and supernatant water correctly.

The interface level meter of the present invention transmits an ultrasonic wave or light and receives ultrasonic waves or light reflected in water including a suspended sediment layer, and the suspension based on a signal received by the sensor. A calculation unit that calculates the position of the interface between the sedimentary layer and the supernatant water, the calculation unit integrates the intensity of the received signal in the time direction, compares the integrated value with a predetermined threshold, and compares the result Based on the above, the position of the interface is calculated.

  In this interface level meter, the sensor performs transmission of ultrasonic waves or light and reception of reflected waves a plurality of times, and the calculation unit accumulates an average value of the intensity of the plurality of received signals in the time direction, And the predetermined threshold value, and the position of the interface is preferably calculated based on the comparison result.

  In the interface level meter, the calculation unit performs a division process of dividing the integrated value by a predetermined value, compares the division result with the predetermined threshold value, and determines the position of the interface based on the comparison result. It is preferable to calculate.

  In the interface level meter, the calculation unit performs a subtraction process for subtracting a predetermined value from the integrated value, compares the subtraction result with the predetermined threshold value, and calculates the position of the interface based on the comparison result. It is preferable to do.

The interface level meter according to the present invention preferably further includes a display unit that displays the position of the interface calculated by the calculation unit.

  According to the present invention, the position of the interface can be accurately detected based on the reflected wave from the interface even when foreign matters such as bubbles, suspended sludge, and pipes exist between the sensor and the interface.

It is a schematic block diagram of the interface level meter which concerns on the 1st Embodiment of this invention. It is a schematic block diagram of the ultrasonic sensor which concerns on the 1st Embodiment. It is a graph which shows an example of ultrasonic reflection intensity distribution. It is a graph which shows an example of ultrasonic reflection intensity distribution. It is a figure which shows the state in which the pipe is provided between the ultrasonic sensor and the interface. It is a graph which shows an example of ultrasonic reflection intensity distribution. It is a graph which shows an example of integrated value distribution of ultrasonic reflection intensity. It is a graph which shows an example of integrated value distribution of ultrasonic reflection intensity. It is a graph which shows an example of integrated value distribution of ultrasonic reflection intensity. It is a graph which shows an example of integrated value distribution of ultrasonic reflection intensity. It is a schematic block diagram of the interface level meter by a modification. It is a figure which shows an example of the correspondence of a digital signal value and a color tone. It is a schematic block diagram of the interface level meter by a modification. It is a figure which shows an example of image data. It is a figure which shows an example of the display by a display part. It is a figure which shows an example of the several storage area provided in memory.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[First Embodiment]
FIG. 1 shows a schematic configuration of the interface level meter according to the first embodiment. The interface level meter includes a signal generation circuit 1, an ultrasonic sensor 2, an amplification circuit 3, an analog / digital converter (hereinafter referred to as an A / D converter) 4, a display unit 5, and an interface level calculation unit 6. .

  As shown in FIG. 2, the ultrasonic sensor 2 has a transmitter 21 and a receiver 22, and has a predetermined height of a treatment tank 25 that stores a suspended sediment layer 23 such as sludge and its supernatant 24. It is attached by an attachment mechanism (not shown). The transmission unit 21 applies the electric signal generated by the signal generation circuit 1 to the ultrasonic transducer, and transmits the ultrasonic wave toward the bottom surface of the processing tank 25.

  The ultrasonic waves transmitted from the transmission unit 21 are reflected by the interface 26 between the suspension deposit layer 23 and the supernatant water 24, the suspension below the interface 26, the bottom surface of the treatment tank 25, and the like. The reflected wave is received by the receiving unit 22. The receiving unit 22 outputs the received signal to the amplifier circuit 3.

  As shown in FIG. 1, the reception signal from the reception unit 22 of the ultrasonic sensor 2 is amplified by the amplification circuit 3 and converted into a digital signal by the A / D converter 4, and then the display unit 5 and the interface level calculation unit 6. Is output.

  Based on the digital signal received from the A / D converter 4, the display unit 5 displays a graph showing a change in reflection intensity (reception intensity) over time from ultrasonic transmission in the display area 51. For example, as shown in FIG. 3, the display area 51 displays a graph with elapsed time on the vertical axis and reflection intensity on the horizontal axis. In addition, since the time from ultrasonic transmission to reception corresponds to the depth of the reflection position of the ultrasonic wave, the vertical axis can be displayed as the depth. As described above, the display area 51 of the display unit 5 can display the latest ultrasonic reflection intensity distribution in the processing tank 25.

  The display area 52 of the display unit 5 displays the position of the interface 26 (see FIG. 2) between the suspension sediment layer 23 and the supernatant water 24 calculated by the interface level calculation unit 6 by a method described later. In the display area 52, the position of the interface 26 may be displayed numerically or as a trend graph.

  The interface level calculation unit 6 calculates the position (depth) of the interface 26 between the suspension sediment layer 23 and the supernatant water 24 based on the digital signal received from the A / D converter 4. A method for calculating the position of the interface 26 by the interface level calculation unit 6 will be described.

  First, as shown in FIG. 2, a case where foreign matters such as bubbles, floating sludge, and pipes are not present between the ultrasonic sensor 2 and the interface 26 will be described. In this case, the reflection intensity of the ultrasonic waves changes as shown in FIG. 4 with the passage of time from the ultrasonic transmission. The interface level calculation unit 6 calculates the distance to the interface 26 (position of the interface 26) based on the elapsed time (t1) until the timing when the reflection intensity exceeds the predetermined threshold value Rth and rapidly increases.

  Moreover, the interface level calculation part 6 can calculate the distance to the bottom face of the processing tank 25 from the elapsed time (t2) until the timing when the reflection intensity suddenly increases after the time t1. The interface level calculation unit 6 holds a table indicating the correspondence between the attachment position of the ultrasonic sensor 2 and the distance to the bottom surface of the processing tank 25, and obtains the distance to the bottom surface with reference to this table. Also good.

  Next, a case where foreign matters such as bubbles, suspended sludge, and pipes exist between the ultrasonic sensor 2 and the interface 26 will be described. As shown in FIG. 5, when the pipe P exists between the ultrasonic sensor 2 and the interface 26, the reflection intensity of the ultrasonic wave changes as shown in FIG. 6 with the passage of time from the ultrasonic transmission. . Since the pipe P is formed of a solid such as metal or plastic, the intensity of the reflected signal from the pipe P is high. Therefore, the intensity of the reflected signal from the pipe P becomes larger than the threshold value Rth for detecting the interface 26, and there is a possibility that the position of the interface 26 is erroneously detected.

  In the present embodiment, the interface level calculation unit 6 receives received signals from the ultrasonic transmission until a predetermined time T elapses in order to prevent erroneous detection of the position of the interface 26 by the reflected signal from the pipe P. Excluded from signals used for interface position detection. As a result, the interface level calculation unit 6 can accurately detect the interface 26 based on the reflection signal from the actual interface 26.

  The predetermined time T, which is a reception time of a signal that is not used for calculating the interface position, can be determined by various methods. For example, when the position (depth) of the pipe P installed in the treatment tank 25 is known in advance, the predetermined time T can be determined from the position of the pipe P and the propagation speed of the ultrasonic wave.

  In addition, referring to the graph displayed in the display area 51, the user may be able to input and set the predetermined time T via input means (not shown). The input means is, for example, a mouse or a keyboard. Further, the display unit 5 may be configured by a touch panel, and the predetermined time T input by the user via the touch panel may be notified to the interface level calculation unit 6.

  The interface level calculation unit 6 outputs the position of the interface 26 thus calculated to the display unit 5 and displays it on the display area 52. Thereby, the display area 52 can display the latest information of the position of the interface 26 between the suspension deposit layer 23 and the supernatant water 24 in the treatment tank 25. The position of the interface 26 may be any of the distance from the water surface 27 of the supernatant water, the distance from the ultrasonic sensor 2, and the distance from the bottom surface of the treatment tank 25, or may be a distance from other reference points.

  In addition, the interface level calculation unit 6 may output the calculated position information of the interface 26 to the external device 10 such as an external display, an external memory, or an external computer.

  As described above, in the present embodiment, the reception signal from the ultrasonic transmission until the predetermined time T elapses is excluded from the signal used for detecting the interface position, and the depth region corresponding to the predetermined time T is detected as the interface position. Exclude from region. In other words, the interface position is detected using the received signal received after the elapse of the predetermined time T from the ultrasonic transmission. Therefore, even when foreign matters such as bubbles, suspended sludge, and pipes exist between the ultrasonic sensor 2 and the interface 26, it is possible to accurately detect the position of the interface 26 based on the reflected wave from the actual interface 26. it can.

  In the first embodiment, when the amount of accumulated suspensions and particles and the expansion rate are high and the interface 26 is located above the foreign matter such as the pipe P, the interface T is shortened by a predetermined time T. 26 positions can be detected.

  In the first embodiment, when the suspension or particle diameter in the treatment tank 25 is small, the sedimentation rate and the deposition / consolidation concentration rate are lowered, the deposition state in the vicinity of the interface 26 is not constant, and the concentration May be thin and uneven. In such a case, it is preferable to obtain a predetermined time or a predetermined number of reflected signals and average them, and compare the averaged reflected signal with a threshold value Rth to detect the position of the interface 26. Here, the averaging of the reflected signal means that a reflected signal triggered by ultrasonic transmission from the transmitting unit 21 is received a plurality of times within a predetermined time to obtain a plurality of reflected signals, or from the transmitting unit 21 In other words, a plurality of (predetermined number) of reflected signals are obtained by performing a predetermined number of times of reception of the reflected signal triggered by the ultrasonic transmission of the above, and an average value of the plurality of reflected signals is obtained.

  For example, an averaging process unit that performs an averaging process on a plurality of reflected signals is provided between the receiving unit 22 and the amplifier circuit 3, thereby averaging the signals supplied from the receiving unit 22 to the amplifier circuit 3. It can be performed. In addition, an averaging processing unit may be provided between the amplifier circuit 3 and the A / D converter 4, and the averaging process may be performed on the signal supplied from the amplifier circuit 3 to the A / D converter 4. Alternatively, an averaging processing unit may be provided so as to perform an averaging process on the digital signal output from the A / D converter 4, or the interface level calculation unit 6 may perform the averaging process. .

  The longer the acquisition time of the reflected signal to be averaged, in other words, the more the number of acquisitions of the reflected signal to be averaged, the better the interface position detection accuracy, but the longer the time required for detection, The followability to the change in the interface position decreases. From the viewpoint of detecting a value in accordance with the change in the interface position, it is preferable to average five or more reflected signals acquired in 1 to 60 seconds.

[Second Embodiment]
The interface level meter according to the second embodiment has the same configuration as the interface level meter according to the first embodiment shown in FIG. This embodiment is different from the first embodiment in the method of detecting the position of the interface 26 by the interface level calculation unit 6.

  In the present embodiment, the interface level calculation unit 6 integrates the received signal intensity in the time direction (that is, the direction toward the bottom surface of the processing tank 25), and compares the integrated value with a threshold value to detect the position of the interface. .

  For example, as shown in FIG. 5, when a pipe P exists between the ultrasonic sensor 2 and the interface 26 and a change in the reflection intensity of the ultrasonic wave as shown in FIG. 6 occurs, the integrated value of the reflection intensity. Is as shown in FIG. The interface level calculation unit 6 compares the integrated value with the threshold value Rth1, and detects the position where the integrated value exceeds the threshold value Rth1 as the position of the interface 26.

  When a foreign matter having a high reflection intensity such as the pipe P is present above the interface 26, the incident wave to the interface 26 becomes small, so the reflected wave from the interface 26 also becomes small. In this embodiment, since the reflection intensity from the interface 26 is added to the reflection intensity from the foreign matter by performing the reflection intensity integration process, the position of the interface 26 is accurately detected by comparison with the threshold value Rth1. Can do.

  The interface level calculation unit 6 may output the integrated value of the reflection intensity to the display unit 5 and display the integrated value distribution of the reflection intensity as shown in FIG.

  In the second embodiment, when the suspension or particle diameter in the treatment tank 25 is small, the sedimentation rate and the deposition / consolidation concentration rate are lowered, the deposition state in the vicinity of the interface 26 is not constant, and the concentration May be thin and uneven. In such a case, it is preferable to obtain a predetermined time or a predetermined number of reflected signals and average them, and compare the average value of the averaged reflected signals with the threshold value Rth1 to detect the position of the interface 26.

  For example, the interface level calculation unit 6 averages a plurality of reflected signals, and obtains an integrated value of the averaged reflected signals. Alternatively, the interface level calculation unit 6 may perform an integration process on each of the plurality of reflected signals, perform an averaging process on the plurality of integrated values, and then compare with the threshold value Rth1.

  By performing such reflection signal averaging processing and integration processing, the layer change in the suspension deposit layer 23 appears as a change in curvature, so the layer interface in the suspension deposit layer 23 is detected. can do. For example, as shown in FIG. 8, the position of the upper surface (interface 26) of the interference sedimentation layer can be detected by the threshold value Rth1, and the interface position between the interference sedimentation layer and the deposition concentrated layer can be detected by the threshold value Rth2.

  The longer the acquisition time of the reflected signal to be averaged, in other words, the more the number of acquisitions of the reflected signal to be averaged, the better the interface position detection accuracy, but the longer the time required for detection, The followability to the change in the interface position decreases. From the viewpoint of detecting a value in accordance with the change in the interface position, it is preferable to average five or more reflected signals acquired in 1 to 60 seconds.

  In the second embodiment, the interface level calculation unit 6 may perform a division process of dividing the integrated value of the received intensity by a predetermined value (a value greater than 1). By this division processing, the reflected wave component from the foreign matter such as the pipe P included in the integrated value can be reduced. For example, the integrated value of the reflection intensity shown in FIG. 7 becomes as shown in FIG. 9 by the division process. By reducing the reflected wave component from the foreign matter, the interface determination focusing on the reflected wave from the suspension deposit layer 23 becomes easy, and the detection accuracy of the interface position can be further improved. This division process may be performed on the values obtained by performing the averaging process and the integration process described above.

  In the second embodiment, the interface level calculation unit 6 may perform a subtraction process (shift process) for subtracting a predetermined value from the integrated value of the received intensity and shifting the integrated value. By this subtraction process, the reflected wave component from the foreign matter such as the pipe P included in the integrated value can be reduced. For example, the integrated value of the reflection intensity shown in FIG. 7 becomes as shown in FIG. 10 by the subtraction process. By reducing the reflected wave component from the foreign matter, the interface determination focusing on the reflected wave from the suspension deposit layer 23 becomes easy, and the detection accuracy of the interface position can be further improved. You may perform this subtraction process with respect to the value which performed the averaging process and integration process mentioned above.

  In the second embodiment, the interface level calculation unit 6 multiplies the reception intensity integrated value by a predetermined coefficient a, adds the predetermined value b to the multiplication result, and compares the calculation result with a threshold value. Then, the position of the interface may be detected. The coefficient a and the predetermined value b are arbitrary real numbers for simply displaying the concentration distribution in the suspension deposit layer 23. By displaying the integrated value of the received signal strength subjected to such multiplication processing and addition processing, the state in the processing tank 25 can be grasped in more detail.

[Another embodiment]
In the interface level meter according to the first and second embodiments, in order to display the ultrasonic reflection intensity in gray scale or color, as shown in FIG. 11, the interface according to the first and second embodiments described above. A graphic conversion unit 7 may be provided in the level meter. The graphic converter 7 converts the value of the digital signal received from the A / D converter 4 into a value (pixel data) corresponding to the gradation of the display. For example, in a color image, each of the three colors red (R), green (G), and blue (B) is represented by k bits (= ^2k gradations, k is an integer of 2 or more), as shown in FIG. With this contrast, 256 colors can be expressed.

  The graphic conversion unit 7 outputs the generated pixel data to the external device 10. When the external device 10 is a display, the ultrasonic reflection intensity is displayed in gray scale or color.

  Further, as shown in FIG. 13, the interface level meter may be provided with a memory 8 for storing pixel data generated by the graphic conversion unit 7. As shown in FIG. 14, the memory 8 arranges m (m is an integer of 2 or more) pixel data 60 corresponding to one reflected signal in one column to form one pixel column, and n (n is 2 or more). Image data is created by arranging pixel rows of (integer) reflected signals in order of acquisition time. The memory 8 outputs this image data to the display unit 5 and displays it in the display area 53. Thereby, the user can monitor the state change in the processing tank 25 with a color image as shown in FIG. The depth display (scale) may be based on the water surface, or may be based on the bottom surface of the sensor or the bottom of the water tank. The memory 8 may output such image data to the external device 10.

  As shown in FIG. 16, the memory 8 may be provided with a plurality of storage areas S1 to Sy. When the storage areas S1 to Sy receive m + w (w is an integer equal to or greater than 0) pixel data from the graphic conversion unit 7, the storage areas S1 to Sy store the display data (pixel string data) d for one pixel column in the display area 53. The storage areas S1 to Sy discard (erase) the oldest data d2 among the data stored so far as new data d1 is stored.

  Each of the storage areas S1 to Sy can store n + x pieces of display data d (x is an integer of 0 or more). As shown in FIG. 16, the display data d includes not only m + w pixel data for color display received from the graphic conversion unit 7, but also the interface level LV received from the interface level calculation unit 6, a water temperature sensor (not shown). The water temperature T and the time C received from may be included, and these may be output to the display unit 5.

  The storage areas S1 to Sy receive the next new display data d from the graphic conversion unit 7 and store it with a set interval (time interval). Of n + x display data (pixel array data) d stored in the storage areas S1 to Sy, the transition of the ultrasonic reception intensity distribution is displayed in color in the display area 53 by using n newest ones. Can do. Further, when the interface level LV and the water temperature T are included in the display data, the display region 53 can display the transition of the interface level and the water temperature together with the color image or alone (erasing the image data). .

  Different intervals are set in the storage areas S1 to Sy. For example, the storage area S1 is set to 1 second, the storage area S2 is set to 3 seconds, the storage area Sy-1 is set to 50 minutes, the storage area Sy is set to 100 minutes, and the display area 53 has 200 pixel columns (n = 200) Consider the case.

  At this time, using the data in the storage area S1, the display area 53 can display a transition with a display width of 200 seconds (= 1 second × 200). Similarly, when the data in the storage area S2 is used, the display width is 10 minutes (= 3 seconds × 200), and when the data in the storage area Sy−1 is used, the display width is about 7 days (≈50 minutes × 200). Using data, it is possible to display the transition of a display width of about 14 days (≈100 minutes × 200).

  Therefore, the time width of the transition (see FIG. 15) of the ultrasonic reception intensity distribution displayed in color in the display area 53 of the display unit 5 can be changed depending on which storage area the display data is used. The control unit 9 controls the display unit 5 so that display data stored in the storage area corresponding to the instructed time width is output to the display unit 5 based on the instruction to switch the time width to be displayed.

  Even when the change in intensity distribution over a long time width is displayed on the display unit 5, it is only necessary to hold a data sampling interval to hold n or n + x pieces of display data d, and hold data for all the time. Therefore, the storage capacity of the memory 8 can be reduced.

  Further, when switching the time width of the display screen, it is only necessary to switch the display data extraction destination from among the plurality of storage areas S1 to Sy in the memory 8, and it is not necessary to perform data thinning out extraction or the like. Time can be shortened and display errors can be prevented.

  The data sampling intervals of the storage areas S1 to Sy may correspond to the time width displayed in the display area 53. For example, when it is desired to store display data for a time width of 3 at n = 200 in the storage area S1, the data sampling interval is 0.9 seconds (= 180 seconds ÷ 200). Similarly, when it is desired to store display data having a time width of 30 minutes in the storage area S3, the data sampling interval is 9 seconds (= 1800 seconds ÷ 200). The control unit 9 may control the data sampling intervals of the storage areas S1 to Sy.

  In the above embodiment and the modification, the interface level meter may use a reflective optical turbidity concentration measuring device instead of the ultrasonic sensor.

  In addition, this invention is not limited to the said embodiment, A component can be deform | transformed and embodied in the range which does not deviate from the summary. In addition, various inventions can be formed by appropriately combining a plurality of components disclosed in the embodiment. For example, some components may be deleted from all the components shown in the embodiment. Furthermore, constituent elements over different embodiments may be appropriately combined.

DESCRIPTION OF SYMBOLS 1 Signal generation circuit 2 Ultrasonic sensor 3 Amplification circuit 4 A / D converter 5 Display part 6 Interface level calculation part 7 Graphic conversion part 8 Memory 9 Control part

Claims (5)

A sensor for transmitting ultrasonic waves or light and receiving ultrasonic waves or light reflected in water including a suspended sediment layer;
Based on the signal received by the sensor, a calculation unit that calculates the position of the interface between the suspension sediment layer and the supernatant water;
With
The interface level meter characterized in that the calculation unit integrates the intensity of the received signal in a time direction, compares the integrated value with a predetermined threshold value, and calculates the position of the interface based on the comparison result. The sensor performs transmission of ultrasonic waves or light and reception of reflected waves a plurality of times,
The calculation unit is configured to integrate an average value of a plurality of received signals in a time direction, compare the integrated value with the predetermined threshold value, and calculate the position of the interface based on a comparison result. The interface level meter according to claim 1 . The calculation unit performs a division process of dividing the integrated value by a predetermined value, compares the division result with the predetermined threshold value, and calculates the position of the interface based on the comparison result. The interface level meter according to 1 or 2 . The calculating unit performs a subtraction process subtracting the predetermined value from the accumulated value, the subtraction result is compared with the predetermined threshold value, according to claim 1, characterized in that to calculate the position of the interface on the basis of the comparison result or interface level meter according to. Interface level meter according to any one of claims 1 to 4, further comprising a display unit for displaying the position of the interface which has been calculated by the calculation unit.

Images