JP2008309560A - Ultrasonic liquid level meter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To confirm whether ultrasonic converters of a liquid level meter are placed in an appropriate angular position relative to a liquid level. <P>SOLUTION: A plurality of the ultrasonic converters 4, 5, 6 are disposed in an ultrasonic liquid level meter, and transmit and receive ultrasonic waves to/from the liquid level. A transmission section 22 transmits pulse waves from the ultrasonic converters 4, 5, 6. A reception signal is obtained by an amplifier 23 and an A/D converter 25 from reception waves received by the ultrasonic converters 4, 5, 6. A liquid level echo strength measurement section 26 measures a strength of a liquid level echo from the reception signal in each direction. An annunciation control section 24 announces a biased state of the liquid level echo strength on single circumference in each direction by use of the measured strength of the liquid level echo. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an ultrasonic liquid level gauge that detects a liquid level based on reception timing of an ultrasonic liquid level echo transmitted to a liquid level. Specifically, the present invention provides a method for confirming whether the ultrasonic transducer of the liquid level gauge is at an appropriate angular position with respect to the liquid level.

  There are two types of ultrasonic liquid level gauges: a liquid level detection type and a liquid level detection type. Ultrasonic level gauge of the liquid level detection type is equipped with an ultrasonic transducer above the liquid level, emits ultrasonic waves into the gas from above the liquid level, reflects off the liquid level and returns. Receive ultrasonic waves. An ultrasonic level gauge of the subsurface detection type is equipped with an ultrasonic transducer below the liquid level, emits ultrasonic waves into the liquid from below the liquid level, reflects off the liquid level and returns. Receive ultrasonic waves. In the subsurface detection type, for example, an ultrasonic transducer is installed on the outer wall surface of the bottom of the LPG tank, and the ultrasonic waves are emitted upward to pass through the bottom steel plate of the LPG tank and propagate through the LPG liquid. Reflected by the liquid surface, the reflected wave propagates through the LPG liquid, passes through the bottom steel plate of the LPG tank, and is received by the same ultrasonic transducer, and the remaining amount of liquid is displayed by measuring the ultrasonic propagation delay time. Something to do is also included. In addition, the ultrasonic liquid level meter has a method that uses the same ultrasonic transducer for both transmission and reception, and a method that receives reflected waves with an ultrasonic transducer that is different from the ultrasonic transducer that emits ultrasonic waves. There is.

For example, Patent Document 1 discloses an ultrasonic level meter having a self-diagnosis function such as operation check and communication check. In this ultrasonic level meter, for example, an operation check is performed by executing a self-diagnosis function, and a disconnection or a short circuit of the sensor can be detected. Moreover, the reliability of the liquid level detection can be confirmed by the self-diagnosis function.
Here, for example, when an ultrasonic wave is emitted from the ultrasonic sensor, the echo pulse wave is returned a plurality of times. (1) A sensor mounting defect (a gap between the sensor and the wall of the storage tank or the container) Self-diagnosis of the sensor function by detecting deterioration in reliability caused by the presence of foreign matter such as deposits at the bottom of the storage tank or container, and (3) quality deterioration of the sensor itself. Like to do.

The reflected wave from the liquid level can be received with any of the ultrasonic liquid level gauges: liquid level detection type, liquid level detection type, or ultrasonic transducer transmission / reception non-transmission / reception non-transmission type. It is necessary to install an ultrasonic transducer in accordance with the direction in which the ultrasonic waves are emitted and the direction in which the ultrasonic waves are received. If the installation direction of the ultrasonic transducer is not appropriate with respect to the liquid level, an error may occur in the measurement of the liquid level, or there may be a situation where erroneous measurement or measurement is impossible.
For example, an ultrasonic transducer installed on the outer wall of the bottom surface of the LPG tank needs to be installed at a position where the bottom surface of the LPG tank is horizontal so that the ultrasonic wave moves vertically with respect to the liquid level. In this case, since the reflected wave does not return to the position of the ultrasonic transducer and cannot be received, the liquid level cannot be measured, the remaining amount of gas cannot be grasped, and in the worst case, the gas may run out.

Conventionally, as a countermeasure against such a mounting deviation of the ultrasonic transducer, there has been a method in which the horizontal position of the bottom surface of the LPG tank is confirmed by using a level when the ultrasonic transducer is installed. However, in this case, a leveler is required, and it is necessary to accurately attach the ultrasonic transducer to the marking after marking the horizontal position confirmed by the leveler accurately. As another countermeasure, the ultrasonic liquid level gauge itself had a function to check whether the intensity of the liquid level echo was at a predetermined level, and a check operation was performed before the operation started. Depending on the liquid level, the liquid level echo may become strong, and even if there is a displacement of the ultrasonic transducer, it could not be detected.
As described above, in the conventional ultrasonic liquid level gauge, it may be difficult to accurately adjust the mounting angle of the ultrasonic transducer with respect to the liquid level, or even a check function may be insufficient.

  Further, as in Patent Document 1, the conventional liquid level gauge also has a function of diagnosing an ultrasonic echo state as a self-diagnosis function. However, since the conventional liquid level gauge only determines and outputs whether or not the sensor is attached, if the sensor is misaligned, it has not been known in which direction the sensor should be corrected.

  The present invention has been made in view of the above circumstances, and in an ultrasonic liquid level gauge that detects a liquid level based on the reception timing of an ultrasonic liquid level echo transmitted to the liquid level, An object of the present invention is to provide an ultrasonic liquid level gauge capable of confirming whether or not the ultrasonic transducer is at an appropriate angular position with respect to the liquid level.

In order to solve the above points, the present invention has the following configuration.
<Configuration 1>
A liquid level meter that detects the liquid level based on the reception timing of the ultrasonic level echo transmitted to the liquid level, and a plurality of ultrasonic transducers are arranged, and a pulse wave is transmitted from each ultrasonic transducer. A transmitting means for transmitting, a receiving means for obtaining a received signal from each of the ultrasonic transducers, a liquid surface echo intensity measuring means for measuring the intensity of a liquid surface echo in each direction on a single circle from the received signal, Means is provided for notifying a deviation state of the liquid surface echo intensity in each direction on the circumference.

<Configuration 2>
The notification means is a display that clearly indicates the position and direction in which the ultrasonic transducer should be attached in order to capture the liquid level echo.

<Configuration 3>
The notification means is a sound generator that clearly indicates the position and direction in which the ultrasonic transducer should be attached in order to capture the liquid level echo.

<Configuration 4>
The notification means is characterized in that the direction of the position where the ultrasonic transducer is to be attached in order to capture the liquid level echo is the direction in which the liquid level echo intensity appears strongly.

<Configuration 5>
The notification means notifies the determination result of whether or not the position where the ultrasonic transducer is attached is appropriate.

  According to the present invention, by examining the echo intensity of each ultrasonic transducer arranged on a single circle and clearly indicating the direction in which the echo intensity appears, it is possible to correct in which direction the mounting position of the ultrasonic transducer is corrected. It becomes clear whether it is good, and the installation position of the ultrasonic transducer can be guided to the optimum position for capturing the liquid level echo more stably. Therefore, the ultrasonic transducer can be attached accurately and efficiently. In addition, since the evaluation of the biased state of the echo intensity is performed to determine whether or not the mounting position is good, the mounting state can be checked accurately before operation, and measurement problems after operation due to defective mounting positions of the ultrasonic transducer can be prevented.

Hereinafter, embodiments of the present invention will be described using specific examples.
<Embodiment 1>
FIG. 1 is a configuration diagram of an ultrasonic liquid level gauge according to Embodiment 1 of the present invention. In FIG. 1, the ultrasonic liquid level gauge mainly includes ultrasonic transducers 4, 5, 6, a control unit 14, and LEDs 7 to 12 installed on the bottom outer wall of the tank 1. The control unit 14 includes a transmission unit 22, an amplifier 23, an A / D converter 25, a liquid surface echo intensity measurement unit 26, a notification control unit 24, a dot matrix display 16, and two LEDs 19 and 20. And speaker 21.

  FIG. 2 is an overview of the ultrasonic liquid level gauge according to Embodiment 1 of the present invention. In FIG. 2, three ultrasonic transducers 4, 5, and 6 are housed in a cylindrical case 3 and are arranged on a single circumference. In the case 3, the LEDs 7 to 12 are also mounted on a single circle. The case 3 and the control unit 14 are connected by a cable 13, and the electrical wiring of the ultrasonic transducers 4, 5, 6 and the LEDs 7 to 12 passes through the cable 13. A display 15 for displaying the liquid level, a dot matrix display 16, two LEDs 19 and 20, and a speaker 21 are mounted on the front side of the control unit 14. The dot matrix display 16 shows an illustration 17 of case 3 including three ultrasonic transducers and six LEDs.

FIG. 3 is a flowchart showing the operation of the ultrasonic liquid level gauge according to the first embodiment of the present invention.
In FIG. 3, first, pulse waves are simultaneously emitted from the ultrasonic transducers 4, 5, and 6 in step S <b> 101, and then received waves of the respective ultrasonic transducers are amplified by the amplifier 23 in step S <b> 102, and the A / D converter 25. A / D conversion is performed to obtain a received signal data string. Next, in step S103, the maximum amplitude of each received signal is searched for as the liquid surface echo intensity.

Next, in step S104, the maximum value Pmax in each liquid surface echo intensity is obtained. Next, in step S105, it is checked whether or not the maximum value Pmax of the liquid surface echo intensity is greater than or equal to a predetermined lower limit value. If Pmax is less than the lower limit value, it is determined that the liquid level echo is in a very weak state, and all the LEDs 7 to 12 are turned off in step S106, and the process proceeds to step S113.
The LEDs 7 to 12 are turned on for the purpose of indicating the uneven state of the liquid surface echo intensity, but when the liquid surface echo state is extremely weak, the LEDs 7 to 12 are all turned off to notify that the liquid surface echo is weak. It is.

  If Pmax is equal to or greater than the lower limit value in step S104, the deviation state of the liquid surface echo intensity is displayed. For this purpose, the process proceeds to step S107, and the number n of ultrasonic transducers having a liquid surface echo intensity in the vicinity of Pmax, for example, 0.9 Pmax or more is obtained.

As a result of some determinations of n in step S108, if n = 1, the process proceeds to step S109, and the LED of the ultrasonic transducer having Pmax is turned on. The lighted LED indicates a direction in which the liquid surface echo intensity is strong.
If n = 2, the process proceeds to step S110, and one LED between the two ultrasonic transducers that are 0.9 Pmax or more is turned on. That is, when the liquid surface echo intensity of the two ultrasonic transducers is strong, the strong direction of the liquid surface echo is regarded as an intermediate direction between the two ultrasonic transducers, and is intermediate between the two ultrasonic transducers. The LED arranged in the direction is turned on.

In the case of n = 3, since the liquid surface echo intensity of all the ultrasonic transducers is almost equal, the process proceeds to step S111, and all the LEDs 7 to 12 are turned on. That is, by turning on the LEDs in all directions, “the liquid surface echo intensity is substantially uniform. ”Is clearly stated. In step S114, the LED 19 of the control unit 14 is turned on by regarding the attachment determination as OK, and clearly indicates the meaning of “attachment OK”. In other cases, that is, after executing steps S109 and S110, the process proceeds to step S112, and an arrow mark in the direction corresponding to the lit LED is displayed on the dot matrix display 16.
After executing Steps S112 and S106, the process proceeds to Step S113, where the LED 20 of the control unit 14 is turned on by regarding the attachment determination NG, and the meaning of “attachment NG” is clearly indicated.

  FIG. 4 is a view showing a state in which the center positions of the single circles of the three ultrasonic transducers installed on the bottom surface of the tank 1 are slightly shifted to the left side. The ultrasonic pulses emitted from the ultrasonic transducers 4, 5 and 6 pass through the bottom steel plate of the tank 1 and travel upward in the liquid. At this time, the ultrasonic bundle of the ultrasonic transducer 6 that is in contact with the surface of the bottom steel plate of the tank 1 that is closest to the horizontal is reflected almost vertically upward at the liquid level 2 toward the substantially vertical direction, and is substantially ultrasonic transducer. Go back to 6. The ultrasonic bundle of the ultrasonic transducer 4 that is in contact with the bottom steel plate surface of the tank 1 being shifted from the most horizontal to the right (the right side is lowered) passes the bottom steel plate of the tank 1 to the right in the liquid. Ascending in the tilted direction, reflecting off the liquid surface 2 and descending in the direction tilted to the right, proceed toward the ultrasonic transducer 6 and return away from the ultrasonic transducer 4. The ultrasonic bundle of the ultrasonic transducer 5 is not inclined as much as the ultrasonic transducer 4 but is slightly shifted to the right, and therefore returns to the position shifted to the right.

  The ultrasonic echoes emitted from the three ultrasonic transducers 4, 5, 6 in this way are the strongest echoes received by the ultrasonic transducer 6 close to the horizontal plane at the bottom of the tank 1, and from the horizontal plane at the bottom of the tank 1. The echo received by the ultrasonic transducer 4 that is greatly deviated becomes the weakest. Since the ultrasonic transducers 4 are arranged on a single circle, when the center of the single circle is aligned with the horizontal plane position of the tank bottom curved surface, the intensity of the received echo of each ultrasonic transducer is uniform.

  FIG. 5 is a diagram showing a transmission pulse waveform (A) and reception signal waveforms (B) to (C) of the ultrasonic transducers 4, 5, and 6. As shown in FIG. 5A, the transmission pulse is composed of three sine wave cycles. The maximum amplitudes of the received signal waveforms (B) to (C) are V4, V5, and V6, respectively, and V6> V5> V4. These maximum amplitudes are used as the echo intensity of each ultrasonic transducer. Therefore, the ultrasonic transducer 6 has the highest echo intensity.

  As described above, since the echo intensity increases as the distance from the horizontal plane at the bottom of the tank increases, the position of the ultrasonic transducer that shows the strongest echo intensity among the ultrasonic transducers arranged on a single circumference is the tank. Will point to the horizontal position of the bottom. Therefore, the direction of the lighted LED among the LEDs 7 to 12 indicates the horizontal plane position direction at the bottom of the tank, and the ultrasonic transducers 4, 5, and 6 may be moved in the direction in which the LED is lighted to correct the mounting position. I understand that. When all the LEDs are lit, the echo intensity is uniform, so the center of the single circle of the ultrasonic transducers 4, 5, 6 coincides with the horizontal plane position at the bottom of the tank, and the ultrasonic transducer is attached. The position is considered correct.

  In this embodiment, the ultrasonic transducers 4, 5, and 6 are also used for obtaining the liquid level measurement value. The operator operates an operation button (not shown) provided on the control unit 14 of the liquid level gauge to perform an operation for correcting the mounting positions of the ultrasonic transducers 4, 5, and 6 as described above, and then the operation mode. Switch to. Then, the control unit 14 periodically emits a pulse wave from the ultrasonic transducers 4, 5, 6, receives the liquid level echo, calculates the liquid level height from the reception timing of the liquid level echo, and determines the liquid level. Is displayed every time.

  As described above, the ultrasonic transducers 4, 5, and 6 are also used for liquid level measurement. However, an ultrasonic transducer group dedicated to liquid level measurement may be provided. In this case, the ultrasonic transducers 4, 5, and 6 are arranged so that the center of the ultrasonic transducer group dedicated to liquid level measurement is aligned with the center of a single circle. The ultrasonic transducer group dedicated to liquid level measurement may be a single ultrasonic transducer.

  In the above embodiment, the number of ultrasonic transducers is three, but may be two, or four or more. When there are two ultrasonic transducers, only one axial displacement can be detected, but for example, it is installed on the bottom of a horizontal cylindrical tank (that is, a cylindrical curved surface) and only the circumferential displacement needs to be considered. It is also conceivable that two ultrasonic transducers can function sufficiently.

  Moreover, in the said Example, although the correction direction of the attachment position was displayed with six LED with respect to three ultrasonic transducers, you may make the number of LEDs into three, the same number as an ultrasonic transducer. Conversely, the number of LEDs may be increased, for example, nine LEDs are arranged for three ultrasonic transducers. In this case, two LEDs are arranged in the middle between the ultrasonic transducers. When the echo intensity of the ultrasonic transducers on both sides is 0.9 Pmax, the LED near the ultrasonic transducer that was Pmax is turned on.

In the said Example, six LED7-12 was arrange | positioned in the cylindrical case 3, and the biased state of echo intensity was displayed. As another display method, as illustrated in FIG. 2, the illustration 17 of the cylindrical case 3 may be displayed on the dot matrix display 16 of the control unit 14, and the LEDs 7 to 12 on the illustration may be lit. Moreover, you may display the arrow 18 which shows the direction which corrects the attachment position of the ultrasonic transducers 4, 5, and 6 at this time.
Further, instead of displaying the echo intensity bias state, the echo intensity bias state may be notified by voice from the speaker 21 arranged in the control unit 14. For example, define the front / rear / left / right direction in advance, and attach it to the right side. You may make it carry out a voice guide.

  In the above embodiment, the attachment determination result is displayed on the control unit 14 on the LEDs 19 and 20. However, the attachment determination result may be notified by sounding “attachment OK” from the speaker 21 by voice.

It is a block diagram of the ultrasonic type liquid level gauge which concerns on embodiment of this invention. It is a general-view figure of the ultrasonic level gauge concerning the embodiment of the present invention. It is a flowchart which shows operation | movement of the ultrasonic-type liquid level meter which concerns on embodiment of this invention. It is the figure which showed the state which the center position of the single circle of the three ultrasonic transducers installed in the bottom face of a tank has shifted | deviated to the left side a little. It is the figure which showed the transmission pulse waveform and the received signal waveform of each ultrasonic transducer.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Tank, 2 ... Liquid level, 3 ... Cylindrical case, 4, 5, 6 ... Ultrasonic transducer, 7-12 ... LED, 13 ... Cable, 14 ... Control part, 15 ... Display, 16 ... Dot matrix Display, 17 ... illustration, 18 ... arrow, 19, 20 ... LED, 21 ... speaker, 22 ... transmitting unit, 23 ... amplifier, 24 ... notification control unit, 25 ... A / D converter, 26 ... liquid surface echo intensity Measurement unit.

Claims (5)

In a liquid level gauge that detects the liquid level based on the reception timing of the ultrasonic level echo transmitted to the liquid level,
A plurality of ultrasonic transducers;
Transmitting means for transmitting a pulse wave from each of the ultrasonic transducers;
Receiving means for obtaining a received signal from each of the ultrasonic transducers;
Liquid level echo intensity measuring means for measuring the intensity of the liquid level echo in each direction from the received signal;
A liquid level gauge characterized by comprising means for informing a deviation state of the liquid surface echo intensity in each direction on a single circle.   2. The liquid level gauge according to claim 1, wherein the notification means is a display device that clearly indicates a position direction in which an ultrasonic transducer is to be attached in order to capture a liquid level echo.   The liquid level meter according to claim 1, wherein the notification means is a sound generator that clearly indicates a position and direction in which the ultrasonic transducer is to be attached in order to capture a liquid level echo.   4. The liquid level gauge according to claim 2, wherein the informing means sets a direction in which the ultrasonic transducer is to be attached in order to capture a liquid level echo as a direction in which the liquid level echo intensity appears strongly. .   The liquid level gauge according to claim 1, wherein the notification means notifies a determination result of whether or not a position where the ultrasonic transducer is attached is appropriate.

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