JPH0784044A - Method and apparatus for measuring distance - Google Patents

Abstract

PURPOSE:To provide a method and an apparatus for measuring a distance which can accurately and effectively measure it irrespectively of a distance to an object to be measured, be reduced in size and efficiently measure it. CONSTITUTION:A controller 55 outputs a near distance mode signal to a first switch SW10, a second switch SW20 and an arithmetic circuit 45, and switches both the switches to positions of 'l'. An ultrasonic wave transmitter 44 outputs an ultrasonic wave, which is amplified by a first amplifier 41, and then emitted to an object to be measured from a first sensor 35. A reflected wave is received by a second sensor 36, output as a reflection signal to an adding amplifier 43, and a distance to the object to be measured is calculated by the circuit 45. A calculated result is output to the controller 55, which outputs a far distance mode signal to both the switches when it is smaller than a threshold value TH to switch both the switches to positions of '2', thereby emitting and receiving the wave by using both the sensor 35 and 36.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a distance measuring method and a distance measuring device, and more particularly, to accuracy and reliability of operation.

[0002]

2. Description of the Related Art Generally, there are various types and types of distance measuring devices. For example, an ultrasonic distance measuring device that measures a distance to an object to be measured using ultrasonic waves is one of them. An ultrasonic level meter is one of such ultrasonic distance measuring devices. An ultrasonic level meter emits ultrasonic waves from a sensor to an object to be measured (eg, liquid, powder, etc.),
The distance is measured (the level of the liquid surface or the like is measured) based on the time difference from the ultrasonic waves reflected from the object to be measured.

The principle diagram of the ultrasonic level meter is shown in FIG.
The operating principle will be briefly described. The ultrasonic wave emitted from the sensor 35 provided in the tank 40 hits the stored liquid 33 and is received by the sensor 35. This sensor 35
From the control unit 34, the time difference between the time when the ultrasonic wave is emitted and the time when the reflected ultrasonic wave is received by the sensor 35 is calculated in the control unit 34 to calculate the liquid level. Based on the calculated liquid level, the control unit 34 controls a pump or the like (not shown) to control the tank 40.
Adjust the amount of liquid stored inside.

Generally, an ultrasonic type level meter is called a one-sensor type in which one sensor is used to measure the level of liquid or the like in the tank as described above, and two sensors are used to measure the level of liquid or the like. There is a so-called two-sensor type that performs measurement.

FIG. 8A shows the structure of a one-sensor ultrasonic level meter. The one-sensor ultrasonic level meter 20 includes a power supply 1, a control circuit 2, a sensor 35, and an arithmetic circuit 6. The operation of such a one-sensor ultrasonic level meter 20 will be described. The power supply 1 outputs a drive signal and supplies it to the sensor 35. The sensor 35 emits ultrasonic waves to the object to be measured (liquid 33) stored in the tank based on the received drive signal. Control circuit 2 at the same time when ultrasonic waves are emitted
Switches the sensor 35 to the ready state. The emitted ultrasonic waves hit the object to be measured (liquid 33) and are reflected,
The reflected ultrasonic waves are received and detected by the sensor 35. Here, the distance to the object to be measured (liquid 33), that is, the liquid level in the tank is measured by calculating the time difference from the time when the sensor 35 emits the ultrasonic wave to the time when the reflected ultrasonic wave is detected.

That is, the one-sensor ultrasonic level meter 20 is used for both transmission and reception by switching one sensor, and measures the liquid level in the tank. Thus, in the one-sensor ultrasonic level meter 20,
Since the measurement is performed by two sensors, the structure is simple and economical.

FIG. 8B shows the structure of a two-sensor type ultrasonic level meter. The two-sensor ultrasonic level meter 30 includes a power supply 1, a control circuit 2, a transmission sensor 35, a reception sensor 36, and an arithmetic circuit 6. The operation of such a two-sensor ultrasonic level meter 30 will be described. The power supply 1 outputs a drive signal and gives the drive signal to the transmission sensor 35. The transmission sensor 35 emits ultrasonic waves to the object to be measured (liquid 33) in the tank based on the received drive signal. The emitted ultrasonic waves hit the object to be measured (liquid 33) and are reflected, and are received and detected by the reception sensor 36 as reflected ultrasonic waves. Here, the distance to the object to be measured (liquid 33), that is, the liquid level in the tank is measured by calculating the time difference from the time when the transmitting sensor 35 emits ultrasonic waves to the time when the receiving sensor 36 detects reflected ultrasonic waves. .

As described above, the two-sensor type ultrasonic level meter 30 includes the transmission sensor 35 and the reception sensor 36 each of which is one.
Provide each one and measure the level. With this method, since two sensors are used, the level can be measured more reliably.

[0009]

However, the conventional ultrasonic level meter has the following problems. As described above, the one-sensor ultrasonic level meter 20 uses one sensor to measure the liquid level in the tank. However, normally, the sensor cannot perform an operation for a short time after the transmission because the sensor resonates (so-called linking). That is, if the liquid level in the tank is measured using the one-sensor ultrasonic level meter 20, the reflected ultrasonic waves cannot be received for a short time after the ultrasonic waves are emitted from the sensor 35.

For example, when the level of the liquid filled in the tank is measured by using the one-sensor type ultrasonic level meter 20 (when the liquid level is close to the sensor 35), the liquid is emitted from the sensor 35. The ultrasonic waves are reflected by the liquid 33 immediately after they hit the liquid 33, and the reflected ultrasonic waves are input to the sensor 35 immediately after being emitted and during linking. However, the sensor 35 during linking cannot receive the reflected ultrasonic wave. Therefore, when the liquid 33 in the tank is stored at a level close to the sensor 35, the level measurement of the liquid 33 cannot be performed (see FIG. 8A).

That is, when the level of the liquid 33 is measured using the one-sensor type ultrasonic level meter 20, the reflected ultrasonic wave from the measured object must be input to the sensor after linking. It was necessary to leave a certain distance between the sensors. In other words, 1 ultrasonic level meter 20
Has a problem that it is not possible to reliably measure an object to be measured at a short distance.

On the other hand, a two-sensor type ultrasonic level meter 30
Sends a level measurement of the liquid 33 as described above to the sensor 3
5 and the reception sensor 36 are used. Usually, the size of the output of these sensors is determined by the size of the ultrasonic wave generating element. In particular, the sensor of the two-sensor ultrasonic level meter 30 that performs long-distance measurement requires a high output, so that the ultrasonic wave generating element becomes large and the sensor becomes large. Further, since two large sensors are used as the transmission sensor 35 and the reception sensor 36, the level meter itself becomes large. Further, since two large sensors are provided and the respective sensors are operated, the structure becomes complicated and the device cannot be downsized.

A two-sensor type ultrasonic level meter 30
The two sensors used in the above have substantially the same performance. Therefore, a long distance measurement is performed 2
In the case of the sensor type ultrasonic level meter 30, even if the receiving sensor 36 that only receives is used a sensor that can output a high output like the transmitting sensor 35, there is a problem that the utilization efficiency is poor. .

Therefore, the present invention enables accurate and reliable measurement regardless of the distance to the object to be measured.
Moreover, it is an object of the present invention to provide a distance measuring method and a distance measuring device that can downsize the device and perform efficient measurement.

[0015]

According to a first aspect of the present invention, there is provided a distance measuring method, wherein a driving signal is applied to a first electric-vibration converting element to emit a vibration to an object to be measured in the short distance mode. The reflected vibration from is received by the second electric-vibration conversion element to obtain a reflected signal, and the distance to the object to be measured is calculated based on the time difference between the drive signal and the reflected signal. A driving signal is applied to the electric-vibration conversion element and the second electric-vibration conversion element to emit a vibration to the object to be measured, and the reflected vibration from the object is measured by the first electric-vibration conversion element and the second element. The electric-vibration conversion element is used to obtain a reflection signal, and the distance to the object to be measured is calculated based on the time difference between the drive signal and the reflection signal.

According to another aspect of the distance measuring device of the present invention, a drive signal is applied to the electric-vibration conversion element to emit a vibration wave to the object to be measured and a reflected wave from the object to be measured is received by the electric-vibration conversion element. A distance measuring device that obtains a reflected wave and calculates the distance to the object to be measured based on the vibration wave and the reflected wave, which is a drive source that outputs a drive signal, and a first electric-vibration connected to the drive source. Conversion element, second electric-vibration conversion element provided at a predetermined distance from the first electric-vibration conversion element, second electric-vibration conversion element
A signal from the first input and a signal from the second input that has a second input connected to the vibration conversion element and a first input connected to the first electric-vibration conversion element, and receives a long-distance mode signal. The distance to the DUT is calculated based on the vibration wave and the reflected wave obtained by mixing, and the DUT is received based on the vibration wave from the first input and the reflected wave from the second input by receiving the short-distance mode signal. A calculation means for calculating the distance between the first electric-vibration conversion element and the second electric-vibration conversion element, and a switch means provided between the first electric-vibration conversion element and the calculation means; The present invention is characterized by including control means for controlling opening / closing and outputting a long distance mode signal and a short distance mode signal to the arithmetic means.

According to a third aspect of the present invention, in the distance measuring device according to the second aspect, the control means outputs a long distance mode signal to the switch means when the calculation result from the calculation means is smaller than a predetermined value. However, when the calculation result is larger than the predetermined value, the control means outputs the short-distance mode signal to the switch means.

A distance measuring device according to a fourth aspect is the distance measuring device according to the second aspect, wherein when the control means outputs the long distance mode signal, the first electric-vibration converting means and the second electric-vibration means. The drive signal pulse applied to both electric-vibration converting means is controlled so that the vibration wave emitted from the converting means causes phase synthesis.

According to a fifth aspect of the distance measuring device, a drive signal is applied to the electric-vibration conversion element to emit a vibration wave to the object to be measured, and a reflected wave from the object to be measured is received by the electric-vibration conversion element. A distance measuring device that obtains a reflected wave and calculates the distance to the object to be measured based on the vibration wave and the reflected wave. The driving source outputs a driving signal, and a plurality of electric-vibration conversions connected to the driving source. A first electric-vibration conversion element group and a second electric-vibration conversion element group composed of elements, a first input and the second electric-vibration conversion element group connected to the first electric-vibration conversion element group It has a connected second input and receives the long-distance mode signal to mix the signal from the first input and the signal from the second input to determine the distance to the DUT based on the vibration wave and the reflected wave. Calculate and receive the short-distance mode signal and the vibration wave from the first input Arithmetic means for computing the distance to the object to be measured based on the reflected wave from the input, receiving the short-distance mode signal and selecting the first electric-vibration conversion element group as transmitting elements, and receiving the long-distance mode signal and Switch means for selecting the first electric-vibration conversion element group and the second electric-vibration conversion element group as transmitting and receiving elements, control means for outputting a long-distance mode signal and a short-distance mode signal to the switch means and the arithmetic means, It is characterized by having.

[0020]

In the distance measuring method and the distance measuring device according to the first and second aspects, the first electric-vibration conversion element and the second electric-vibration conversion element are provided, and the first electric-vibration conversion element is provided in the short-distance mode. Vibration is emitted from the electric-vibration conversion element to the object to be measured, and the second electric-vibration conversion element receives reflected vibration from the object to be measured to calculate the distance to the object to be measured.
In the long-distance mode, vibration is emitted from both the first electric-vibration conversion element and the second electric-vibration conversion element, and the first electric-vibration conversion element and the second electric-vibration conversion element are emitted. The reflected vibration from the measured object is received by both of the above, and the distance to the measured object is calculated. Therefore, linking does not occur in the short-distance mode, and distance measurement can be performed in the long-distance mode.

According to a third aspect of the present invention, in the distance measuring instrument according to the second aspect, the control means outputs the long distance mode signal to the switch means when the calculation result from the calculation means is smaller than a predetermined value. However, when the calculation result is larger than the predetermined value, the control means outputs the short distance mode signal to the switch means. Therefore, the mode can be switched according to the distance to the object to be measured.

A distance measuring device according to a fourth aspect is the distance measuring device according to the second aspect, wherein the first electric-vibration converting means and the second electric-vibration are provided when the control means outputs the long-distance mode signal. The drive signal pulse applied to both electric-vibration converting means is controlled so that the vibration wave emitted from the converting means causes phase synthesis. Therefore, in the long-distance mode, the oscillating waves cause phase synthesis, the oscillating pressure is strengthened, and the directivity is increased.

A distance measuring device according to a fifth aspect is provided with a first electric-vibration conversion element group and a second electric-vibration conversion element group, each of which is composed of a plurality of electric-vibration conversion elements. At, the first electric-vibration conversion element group emits vibration to the object to be measured, and the first electric-vibration conversion element group receives reflected vibration from the object to be measured to calculate the distance to the object to be measured. In the long-distance mode, vibration is emitted from the first electric-vibration conversion element group and the second electric-vibration conversion element group, and the vibration is emitted by the first electric-vibration conversion element group and the second electric-vibration conversion element group. The reflected vibration from the measurement object is received and the distance to the measurement object is calculated. Therefore, it becomes possible to emit a stronger vibration to the object to be measured and receive the reflected wave in a wider area.

[0024]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of an ultrasonic level meter according to the present invention will be described below with reference to the drawings. A configuration circuit diagram of the ultrasonic level meter 50 of the present embodiment is shown in FIG. 1 to describe the configuration. The ultrasonic level meter 50 includes an ultrasonic wave transmission circuit 44 as a drive source, a control circuit 55 as a control unit, switches SW10 and SW20 as a switch unit, and a first sensor 35 as a first electric-vibration conversion element. , A second sensor 36 which is a second electric-vibration conversion element, a first amplifier 41, a second amplifier 42, a summing amplifier 43 and a calculation circuit 45 as calculation means, a plurality of resistors (resistor R1, resistor R2). ) And a plurality of diodes (d1, d2, d3, d4) are provided.

Next, the operation of the ultrasonic level meter 50 will be described. Here, consider a case where the ultrasonic level meter 50 measures the level of the liquid stored in the tank 40. At the time of starting the ultrasonic level meter 50, the short-distance mode signal is output from the control circuit 55 to the switches SW10, SW20 and the arithmetic circuit 45. When receiving the short-distance mode signal, the switches SW10 and SW20 are both switched to the "1" position. When the switch SW10 and the switch 20 are switched in this way, the drive signal from the ultrasonic transmission circuit 44 is input to the first amplifier 41 and is not input to the second amplifier 42.

The drive signal input to the first amplifier 41 is amplified here and input to the first sensor 35. From the first sensor 35, the amplified drive signal is converted into ultrasonic waves and emitted to the object to be measured (liquid). The ultrasonic waves emitted from the first sensor 35 are shown in FIG. 2A. This ultrasonic wave is reflected by the liquid 33 and is input to the second sensor 36 as a reflected ultrasonic wave. FIG. 2B shows reflected ultrasonic waves input to the second sensor 36.

Next, the second sensor 36 converts the reflected ultrasonic wave into a reflected signal (electrical signal) and outputs it to the summing amplifier 43. The reflected signal from the second sensor 36 is input to the summing amplifier 43 through "1" of the switch SW10. As described above, the direct reflection signal from the second sensor 36 and the reflection signal through “1” of the switch SW10 are input to the adding amplifier 43. The addition amplifier 43 adds and amplifies the received reflection signal (the reflection signal directly from the second sensor 36 and the reflection signal through "1" of the switch SW10),
Output to the arithmetic circuit 45. Therefore, the level of the reflected signal is doubled, and matching with the level of the reflected signal in the long-distance mode signal described later can be achieved.

In the arithmetic circuit 45, the summing amplifier 43
The distance to the liquid (the liquid level in the tank) is calculated based on the time difference between the output from the control circuit 55 and the short distance mode signal from the control circuit 55 (that is, the time difference t shown in FIG. 2). In this way, the level of the liquid 33 stored in the tank 40 calculated by the calculation circuit 45 is measured by the ultrasonic level meter 5.
It is output outside 0 and used for controlling the liquid supply pump and the like.

The calculation result is output from the calculation circuit 45 to the control circuit 55. Here, the calculation result is output to the control circuit 55 because the long distance mode signal and the short distance mode signal are switched according to the level of the liquid 33 calculated in the calculation circuit 45. That is,
When the calculation result (the level of the liquid 33) falls below the threshold value TH, the control circuit 55 outputs a long-distance mode signal, so that it is stronger than the ultrasonic waves in FIG. 2A (ultrasonic waves in the short-distance mode signal). This is because reliable measurement of the object to be measured is performed by outputting various ultrasonic waves.

As described above, when the calculation result exceeds the threshold value TH, the control circuit 55 continues to output the short-distance mode signal as it is, and when it falls below the threshold value TH, it outputs the long-distance mode signal.

For example, the operation when the calculation result received by the control circuit 55 is smaller than the threshold value TH and the long-distance mode signal is output will be described. The long-distance mode signal from the control circuit 55 is input to the arithmetic circuit 45, the switch SW10, and the switch SW20. When receiving the long distance mode signal, both the switch SW10 and the switch SW20 are switched to the "2" position. When the switch SW10 and the switch 20 are switched in this way, the ultrasonic waves from the ultrasonic transmission circuit 44 are input to the first amplifier 41 and the second amplifier 42.

At this time, the drive signal pulse output to the ultrasonic wave transmission circuit 44 is output by the control circuit 55 to the first sensor 3
5 and the ultrasonic waves emitted from the second sensor 36 are controlled to cause phase synthesis. The first amplifier 41 and the second amplifier 42 amplify such ultrasonic waves and output them to the first sensor 35 and the second sensor 36. First sensor 35
And the second sensor 36 emits amplified ultrasonic waves to the liquid 33. Note that the ultrasonic intensity here uses two sensors, the first sensor 35 and the second sensor 36, so that when measuring with a short-distance mode signal (FIG. 2A).
It is about twice as large as that of (see FIG. 3).

By the way, normally, the ultrasonic waves emitted from the sensor diffuse at an angle of about 12 degrees. This ultrasonic diffusion is listed in Figure 4A. Further, this ultrasonic wave is a spherical wave as shown in FIG. 4B. However, the drive signals input to the first sensor 35 and the second sensor 36 are controlled so that the ultrasonic pulses emitted from both sensors cause phase synthesis. Therefore, the ultrasonic waves (spherical waves) emitted from the first sensor 35 and the second sensor 36 are phase-combined to form a plane wave as shown in FIG. The angle of the ultrasonic beam by this phase combination is about 12 degrees for short range measurement.
It becomes narrower and has higher directivity.

Further, FIG. 5 shows a beam of ultrasonic waves when phase combination is formed. The ultrasonic beam here is about 5
Spread in degrees. Therefore, the ultrasonic wave from the sensor is diffused (because of the wide beam angle) at the time of the long distance measurement, the tank 40
It is possible to prevent erroneous measurement caused by reflection on the side wall of the. Further, when a plane wave is formed by phase synthesis, the oscillating pressure of ultrasonic waves becomes high and the ultrasonic waves become strong.

As described above, the ultrasonic waves emitted from the first sensor 35 and the second sensor 36 are reflected by the liquid 33 while forming a plane wave by phase synthesis. Here, the intensity of the ultrasonic wave is approximately doubled because it is a signal from two sensors (see FIG. 3), and the oscillating pressure is increased by the phase synthesis, so that the ultrasonic wave becomes even stronger. That is, even if there is a suspended matter in the air in the tank 40, the ultrasonic waves reliably reach the liquid 33. Therefore, reliable and accurate measurement can be performed. From this, if the object to be measured in the tank 40 is a substance that absorbs some ultrasonic waves,
In addition, even if a suspended object is present in the air in the tank 40 due to stirring of the measured object (for example, powder or fluid), the ultrasonic waves can reach the measured object without fail and perform reliable and accurate measurement. It is possible.

FIG. 6 shows a first sensor 35 and a second sensor 36.
An example of a beam in the case where the ultrasonic wave emitted from is reflected on the liquid 33 and is input to the first sensor 35 and the second sensor 36 at the same time will be described. Since the angle of the ultrasonic wave (plane wave) beam from the liquid 33 is about 5 degrees, the reflected ultrasonic wave (plane wave) is input to the first sensor 35 and the second sensor 36 without being diffused. In addition, the area for receiving the reflected ultrasonic waves is about twice as large as the measurement based on the short-range mode signal because two sensors are used. Therefore, reliable measurement can be performed.

The first sensor 35 and the second sensor 36 convert the reflected ultrasonic waves received in a wide area as described above into reflected signals (electrical signals) and output them to the summing amplifier circuit 43 (FIG. 1).

At this time, the reflected signal from the first sensor 35 is input to the summing amplifier 43 directly through the switch SW10 "2" and the reflected signal from the second sensor 36. The summing amplifier 43 sums and amplifies the received reflected signal and outputs the amplified reflected signal to the arithmetic circuit 45. The arithmetic circuit 45 determines up to the liquid 33 based on the time difference (time difference t2 shown in FIG. 3) from the long distance mode signal from the control circuit 55. Calculate the distance of (the liquid level in the tank).

The liquid level in the tank calculated by the calculation circuit 45 is output to a liquid supply pump or the like (not shown) and used for controlling the liquid level and the like. Also here, the arithmetic circuit 45 outputs the arithmetic result to the control circuit 55, and detects whether the arithmetic result falls below the threshold value TH. Here, before the arithmetic operation by the arithmetic circuit 45, amplification is performed by using the addition amplification circuit 43. As a result, a reflection signal with a delayed phase (a reflected ultrasonic wave from an oblique direction with respect to the sensor) is not amplified. Therefore, accurate measurement can be performed.

As described above, when the ultrasonic level meter 50 according to the present invention is used, it is possible to perform a reliable and accurate level measurement according to the increase or decrease of the object to be measured in the tank 40. This is efficient because ultrasonic waves are simultaneously transmitted and received using the sensor. Therefore, since it is not necessary to use a large-sized and high-performance sensor, the size and cost of the device can be reduced. Moreover, since the emitted ultrasonic waves are phase-synthesized, efficient measurement can be performed.

In the above embodiment, the threshold value TH for switching between the short-distance mode signal and the long-distance mode signal is a value corresponding to the distance at which the sensor does not cause linking. For example, the distance from the sensor. Is a value corresponding to about 50 cm to 1 m. Therefore, the ultrasonic wave shown in FIG. 2A as shown in FIG. 7 may be provided with hysteresis to switch between the short distance mode signal and the long distance mode signal. That is, two predetermined values (TH1 and T
H2) is set and switching from the short-distance mode signal to the long-distance mode signal is performed at a predetermined value TH2, and if the value is more than that, the long-distance mode signal is continuously output. On the other hand, switching from the long-distance mode signal to the short-distance mode signal is
In order to avoid frequent switching at the predetermined value TH2, the predetermined value T
It is not performed at H2, but is performed at a predetermined value TH1.

In the above embodiment, the case where the liquid level of the object to be measured stored in the tank 40 is measured has been described. However, it may be used for level measurement for other purposes (for example, fluid flowing through a flow path). Further, although the case where the liquid 33 is used as the measured object has been described as an example, the liquid 33 may be used for measurement of another measured object (for example, powder, granules, fine powder, lump, etc.).

Further, in the above embodiments, the case where the short distance mode signal and the long distance mode signal are automatically switched has been described. However, if the level of the liquid 33 does not change significantly, the SW10
Alternatively, a changeover switch for directly controlling the SW 20 may be provided so that the short distance mode signal or the long distance mode signal can be manually selected arbitrarily.

In the above embodiment, the two sensors, the first sensor 35 and the second sensor 36, are switched according to the distance to the object to be measured, and ultrasonic waves are emitted and reflected ultrasonic waves are received. It has become possible to perform reliable and accurate distance measurement. However, the number of sensors used is 2
Not only one, but by switching three or more sensors and operating as described above, it is possible to perform more reliable and accurate distance measurement, especially when measuring a long distance to the object to be measured. Become.

Further, when the distance is measured by using three or more sensors, it is not necessary to provide the sensors at a predetermined interval from each other as in the above-mentioned embodiment, and the sensors are provided at a predetermined interval from the adjacent sensors. Select the sensors with spacing,
Distance measurement can be performed.

[0046]

The distance measuring method and the distance measuring device according to the first and second aspects are provided with the first electric-vibration converting element and the second electric-vibration converting element, and in the short-distance mode. Vibration is emitted from the first electric-vibration conversion element to the object to be measured, and the second electric-vibration conversion element receives reflected vibration from the object to be measured to calculate the distance to the object to be measured. In the long-distance mode, vibration is emitted from both the first electric-vibration conversion element and the second electric-vibration conversion element, and the first electric-vibration conversion element and the second electric-vibration conversion element are emitted. The reflected vibration from the measured object is received by both of the above, and the distance to the measured object is calculated. That is, linking does not occur in the short-distance mode, and distance measurement can be performed in the long-distance mode.
Therefore, accurate and reliable distance measurement can be performed regardless of the distance of the object to be measured. In the distance measuring device according to claim 3, in the distance measuring device according to claim 2, when the calculation result from the calculating means is smaller than a predetermined value, the control means outputs a long distance mode signal to the switch means, and calculates. When the result is larger than the predetermined value, the control means outputs the short range mode signal to the switch means. That is, the mode can be switched according to the distance to the object to be measured. Therefore, regardless of the distance to the DUT,
It is possible to perform reliable measurement.

A distance measuring device according to a fourth aspect is the distance measuring device according to the second aspect, wherein the first electric-vibration converting means and the second electric-vibration are provided when the control means outputs the long-distance mode signal. The drive signal pulse applied to both electric-vibration converting means is controlled so that the vibration wave emitted from the converting means causes phase synthesis. That is, in the long-distance mode, the vibration waves cause phase synthesis, the vibration pressure is strengthened, and the directivity is increased. Therefore, long-distance measurement is possible.

In the distance measuring device according to the fifth aspect, a first electric-vibration converting element group and a second electric-vibration converting element group each composed of a plurality of electric-vibration converting elements are provided, and a short distance In the mode, vibration is emitted from the first electric-vibration conversion element group to the object to be measured, and the first electric-vibration conversion element group receives reflected vibration from the object to be measured to calculate the distance to the object to be measured. In the long-distance mode, vibration is emitted from the first electric-vibration conversion element group and the second electric-vibration conversion element group, and the vibration is emitted by the first electric-vibration conversion element group and the second electric-vibration conversion element group. The reflected vibration from the measurement object is received and the distance to the measurement object is calculated. That is, it becomes possible to emit a stronger vibration to the object to be measured and receive the reflected wave in a wider area. Therefore, more accurate and reliable distance measurement can be performed.

[Brief description of drawings]

FIG. 1 is a configuration circuit diagram of an ultrasonic level meter according to the present invention.

FIG. 2 is a diagram showing ultrasonic waves emitted from a first sensor and reflected ultrasonic waves input to a second sensor during measurement with a short-distance mode signal.

FIG. 3 is a diagram showing ultrasonic waves emitted and received from a first sensor and a second sensor during measurement with a long-distance mode signal.

FIG. 4 is a diagram showing ultrasonic wave diffusion and waveform during measurement with a long-distance mode signal.

FIG. 5 is a diagram showing a plane wave and an ultrasonic beam formed by phase combination of ultrasonic waves during measurement with a long-distance mode signal.

6 is a diagram showing an example of the ultrasonic beam shown in FIG.

FIG. 7 is a diagram showing hysteresis for switching between a short distance mode signal and a long distance mode signal.

FIG. 8 is a diagram showing a configuration of a conventional ultrasonic level meter.

FIG. 9 is a diagram showing a principle of a conventional ultrasonic level meter.

[Explanation of symbols]

 35-First sensor 36-Second sensor 41-First amplification circuit 43-Adding amplifier 44-Ultrasonic transmission circuit 45- ..Arithmetic circuit 55 ... Control circuit SW10 ... First switch SW20 ... Second switch

Claims (5)

[Claims] 1. In the short-distance mode, a drive signal is applied to the first electric-vibration conversion element to emit vibration to the object to be measured, and reflected vibration from the object to be measured is converted to the second electric-vibration conversion element. To obtain the reflection signal, calculate the distance to the DUT based on the time difference between the drive signal and the reflection signal, and in the long-distance mode, the first electric-vibration conversion element and the second electric-vibration element A drive signal is applied to the conversion element to oscillate vibration to the DUT, and the reflected vibration from the DUT is received by the first electric-vibration conversion element and the second electric-vibration conversion element to obtain a reflected signal. Then, the distance to the object to be measured is calculated based on the time difference between the drive signal and the reflected signal. 2. A drive signal is applied to an electric-vibration conversion element to emit a vibration wave to an object to be measured, and a reflected wave from the object to be measured is received by the electric-vibration conversion element to obtain a reflected wave. A distance measuring device for calculating a distance to an object to be measured based on an oscillating wave and a reflected wave, the drive source outputting a drive signal, a first electric-vibration conversion element connected to the drive source, a first electric A second electric-vibration conversion element provided at a predetermined distance from the vibration conversion element, a second input connected to the second electric-vibration conversion element and connected to the first electric-vibration conversion element Has a first input, and receives the long-distance mode signal, calculates the distance to the DUT based on the vibration wave and the reflected wave obtained by mixing the signal from the first input and the signal from the second input. , When receiving the short range mode signal, the vibration wave from the first input and the reaction wave from the second input are received. Computation means for computing the distance to the object to be measured based on the wave, between the first electric-vibration conversion element and the second electric-vibration conversion element and between the first electric-vibration conversion element and the calculation means A distance measuring device comprising: switch means provided between the control means and control means for controlling opening / closing of the switch means and outputting a long-distance mode signal and a short-distance mode signal to a computing means. 3. The distance measuring device according to claim 2, wherein when the calculation result from the calculation means is smaller than the predetermined value, the control means outputs a long distance mode signal to the switch means and the calculation result is the predetermined value. The distance measuring device, wherein the control means outputs a short-range mode signal to the switch means when the value is larger. 4. The distance measuring device according to claim 2, wherein the control means outputs the vibrations emitted from the first electric-vibration converting means and the second electric-vibration converting means when outputting the long-distance mode signal. So that the waves cause phase synthesis-
A distance measuring device characterized by controlling a drive signal pulse applied to the vibration converting means. 5. An electric-vibration conversion element is provided with a drive signal to emit a vibration wave to an object to be measured, and a reflected wave from the object to be measured is received by the electric-vibration conversion element to obtain a reflected wave. A distance measuring device for calculating a distance to an object to be measured based on an oscillating wave and a reflected wave, comprising: a drive source that outputs a drive signal; and a first electric-vibration conversion element connected to the drive source. An electric-vibration conversion element group and a second electric-vibration conversion element group, a first input connected to the first electric-vibration conversion element group and a second input connected to the second electric-vibration conversion element group. In addition to receiving the long distance mode signal, the distance from the DUT is calculated based on the vibration wave and the reflected wave obtained by mixing the signal from the first input and the signal from the second input, and the short distance mode signal is calculated. In response to the vibration wave from the first input and the reflected wave from the second input. Calculating means for calculating the distance to the object to be measured, receiving the short-distance mode signal, selecting the first electric-vibration conversion element group as transmission elements, and receiving the long-distance mode signal, the first electric-vibration conversion A switch means for selecting the element group and the second electric-vibration conversion element group as a transmitting / receiving element, and a control means for outputting a long-distance mode signal and a short-distance mode signal to the switch means and the arithmetic means. And a distance measuring device.