JPH05256940A - Monitoring apparatus of storing tank - Google Patents

Abstract

PURPOSE:To remove influences of the change of the propagating speed of microwaves upon a measuring value. CONSTITUTION:This monitoring apparatus is so adapted as to detect the storing amount by transmitting frequency-modulated microwaves towards a stored substance in the storing tank and receiving the reflected microwaves from the storing substance. A reference reflecting body is provided inside the storing tank to reflect the frequency-modulated microwaves. After the frequency component of a difference signal corresponding to the reflected wave is analyzed by a first frequency analyzing part 15, the storing amount of the substance is operated by a first storing amount operating part 16 from the ratio of the frequencies of the frequency component indicating the position of the reference reflecting body and the frequency component indicating the position of the reflecting surface of the substance based on the analyzing result.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention determines the difference between the transmission time of an FM modulated microwave and the reception time of a reflected wave from a storage,
The present invention relates to a storage tank monitoring device that detects a storage amount of a stored item by extracting a difference between a frequency at a transmission / reception position of an FM modulated microwave that is a transmission signal and a frequency at a transmission / reception position of a reflected wave from a storage item.

[0002]

2. Description of the Related Art When heavy oil, LPG, LNG or the like is to be stored in a storage tank, it is essential to measure the storage amount for management. Therefore, conventionally, an antenna mounted near the top of the storage tank for transmitting microwaves to the storage side and receiving microwaves reflected by the storage side, and an FM-modulated microwave for this antenna A device including a transmitter for outputting and a mixer for detecting a difference in frequency between a reflected wave from the storage and an FM-modulated wave to be transmitted is used, and the frequency output from the mixer is a top surface of the storage ( In order to show the relationship proportional to the distance between the microwave reflection surface) and the antenna, the storage amount is measured based on the output frequency of the mixer.

[0003]

The antenna in the above device is not limited to the reflected wave from the uppermost surface of the stored object,
The microwaves reflected by the irregularities such as the joints on the inner wall of the storage tank, or the microwaves reflected by the uppermost surface of the storage tank and then again by the upper wall of the storage tank and reflected again by the storage object. Since unnecessary reflected waves such as multiple reflected waves are also guided at the same time, there is a problem that an error occurs in the measured value due to the influence of these unnecessary reflected waves. In addition, if the storage in the storage tank is volatile,
Since the storage tank is filled with the gas in the storage, the dielectric constant in the storage tank changes depending on the degree of gas filling. Therefore, there is a problem in that the microwave propagation speed changes in the storage tank, and the change in the propagation speed deteriorates the measurement accuracy.

The present invention was conceived to solve the above problems, and an object of the present invention is to eliminate the influence of changes in the propagation velocity of microwaves on measured values. The invention according to claim 2 aims to eliminate the influence of unnecessary reflected waves.

[0005]

In order to solve the above-mentioned problems, a storage tank monitoring device according to the invention of claim 1 transmits an FM-modulated microwave toward a stored article in the storage tank, and the FM-modulated microwave is transmitted. Detecting the storage amount of a stored object based on a difference signal indicating a difference between an FM-modulated microwave that is a transmission signal at a microwave transmission / reception position and an FM-modulated microwave that is a reflected wave reflected from a storage direction at the transmission / reception position A reference reflector that is applied to a storage tank monitoring device that performs, and that is provided in a storage tank and that reflects an FM-modulated microwave, and that analyzes the distribution of frequency components of a difference signal.
Of the frequency component analyzed by the first frequency analysis unit and the frequency component of the frequency component indicating the position of the reference reflector and the frequency component indicating the position of the reflection surface of the storage. A configuration including a first storage amount calculation unit that calculates the storage amount of the stored material on the basis of the above is used. The storage tank monitoring apparatus according to the second aspect of the present invention transmits the FM-modulated microwave toward the stored object in the storage tank, and the FM-modulated microwave that is the transmission signal at the transmission / reception position of the FM-modulated microwave. And the frequency of the difference signal when applied to a storage tank monitoring device that detects the storage amount of a stored object based on a difference signal indicating the difference between the FM-modulated microwave that is a reflected wave reflected from the storage direction at the transmitting / receiving position. A second frequency analysis section for analyzing the distribution of the components;
And a second storage amount calculation unit for calculating the storage amount of the stored material based on the frequency of the frequency component of the level indicating the reflection from the stored material among the frequency components analyzed by adopt.

[0006]

According to the invention of claim 1, the distance from the transmitting / receiving position to the reference reflector is indicated by d11 and the distance from the transmitting / receiving position to the storage surface is indicated by d12, and the difference corresponding to the reflected wave from the reference reflector is shown. Assuming that the frequency of the signal is Δf1 and the frequency of the difference signal corresponding to the reflected wave from the stored material is Δf2, the relationship of d11 / d12 = Δf1 / Δf2 is established. And the distance d11 is known and Δ
Since f1 and Δf2 are given as the analysis result of the first frequency analysis unit, the first storage amount calculation unit calculates the distance d12 by performing the calculation of the above equation, and the storage amount based on the calculation result. To calculate. In the invention according to claim 2, the level of the difference signal corresponding to the reflected wave from the stored material is different from the level of the difference signal corresponding to the other reflected waves (generally, it corresponds to the reflected wave from the stored material. Since the difference signal has a higher level than the difference signals corresponding to the other reflected waves), the second storage amount calculation unit outputs the difference from the stored material based on the level of the analysis result of the second frequency analysis unit. The difference signal corresponding to the reflected wave is identified, and the distance to the storage surface is calculated based on the frequency of the frequency component indicating the identified difference signal. Then, the storage amount is calculated according to the calculated distance.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

FIG. 2 is a schematic explanatory view showing the inside of a storage tank of one embodiment when the invention according to claim 1 is applied to a storage tank for storing petroleum.

In the figure, a storage tank for storing oil 36
At the center of the tank top wall 35 of 37, a cylindrical antenna housing 32, one end of which is closed by a housing top wall 322, is provided with a flange with the opening 321 facing downward.
It is fixed by 33, and on the upper part of the housing upper wall 322, a substantially rectangular parallelepiped storage box 31 in which a device for transmitting and receiving microwaves is stored is attached.

Further, an antenna 11 is attached to the lower part of the housing upper wall 322 for transmitting the FM modulated microwave 41 downward and receiving the reflected wave which is the FM modulated microwave from below. Opening of the tank upper wall 35 formed in the same shape as the lower end shape of 32
Along the bottom side around the 351 the antenna housing 32
A reference reflector 34, which is a flat ring formed so that the inner diameter thereof is smaller than the inner diameter of the opening 321, is provided.

FIG. 1 is a block diagram showing an electrical configuration of an embodiment of the invention described in claim 1.

The output from the microwave oscillator 18 for generating the FM modulated microwave is sent to the antenna 11, and the received output of the FM modulated microwave received by the antenna 11 is sent to the mixer 13. Guided to the circulator 12.

The mixer 13 to which the output 121 from the circulator 12 is guided is an FM received by the antenna 11.
This is a block that performs frequency conversion by mixing the modulation microwave and the FM modulation microwave from the microwave oscillator 18 leaking through the circulator 12, and outputs a difference signal that is the conversion result. Mixer
The difference signal 131, which is the output of 13, is introduced into the amplifier 14 whose gain is controlled by the control signal.

The output 141 of the amplifier 14 is led to a frequency analysis section 15 which is a spectrum analyzer composed of an FFT analyzer. Is sent to the storage amount calculation unit 16 which performs the calculation. The output calculated by the storage amount calculation unit 16 is led to a display unit 17 that displays the storage amount.

Further, the output from the control signal generator 19 is led to the microwave oscillator 18 as a control signal for applying FM modulation to the oscillating microwave, and the amplifier 14 has the same control signal generator. The output from 19 is introduced as a signal to control its amplification factor.

In the above structure, the frequency analysis unit 15 corresponds to the first frequency analysis unit according to claim 1, and the storage amount calculation unit 16 corresponds to the first storage amount calculation unit according to claim 1. is doing. The transmission / reception position is near the antenna 11, and more specifically, the circulator 12 position.

FIG. 3 is an explanatory diagram showing the state of signals in the main part of this embodiment, and FIG. 4 is an explanatory diagram showing the analysis result of the distribution of frequency components. In FIG. 3, the horizontal axis indicates time, the vertical axis indicates only the signal 191, and the other signals indicate frequency.

The operation of the first embodiment of the invention will be described below with reference to FIGS. 1 to 4 as necessary.

The control signal generator 19 generates a sawtooth control signal (indicated by 191 in FIG. 3) which is repeated every period t11 and whose level increases linearly in the period t12. 191 to microwave oscillator 18
, The microwave oscillator 18 oscillates an FM-modulated microwave whose frequency increases linearly in the period t12, as indicated by the alternate long and short dash line 41 in FIG.

The FM-modulated microwave 41 is transmitted downward from the antenna 11 via the circulator 12. Then, a part 51 of the transmitted FM modulated microwave 41 is reflected by the reference reflector 34 (shown by 52). Also, most of the FM modulated microwave 41 (indicated by 53) is
Reflected by oil surface 361 (shown by 54).

The reflected wave 52 from the reference reflector 34 and the reflected wave 54 from the oil surface 361 are both received by the antenna 11 and guided to the mixer 13 via the circulator 12.
The distance d11 from the antenna 11 to the reference reflector 34 and the antenna
Since it is different from the distance d12 from the oil surface 361 to the oil surface 361, the reflected wave 52 from the reference reflector 34 is guided to the mixer 13 with a delay time t13 corresponding to the distance d11 as shown by a broken line 42, and The reflected wave 54 from the surface 361 is guided to the mixer 13 with a delay time t14 corresponding to the distance d12, as shown by the solid line 43.

Therefore, at the output 131 of the mixer 13, the reflected wave
As the signal corresponding to 52, the difference signal (shown by the broken line 421) whose frequency is Δf1 is output in the period t15, and as the signal corresponding to the reflected wave 54, the period t16
At, the difference signal whose frequency is Δf2 (shown by the solid line 431) is output.

The amplifier 14 to which these difference signals 421 and 431 are guided, follows the output from the control signal generator 19 and has a period t1.
Since the amplification is stopped at 7, the frequency analysis unit 15
, The signal level thereof is 0 in the period t17, and the difference signals 422 and 432 equal to the difference signals 421 and 431 are introduced in the other periods.

The difference signals 422 and 432 are A / D-converted by the frequency analysis unit 15 according to the already established technique, and then FFT-converted, and the converted output showing the distribution of frequency components is obtained as the frequency component analysis result. It is sent to the storage amount calculation unit 16.

This converted output is, as shown in FIG.
Low frequency component 61 showing t11, frequency component 62 showing reflected wave 52 from the reference reflector 34, reflected wave 54 from petroleum surface 361
Is a signal in which a frequency component 63 indicating the, and a minute frequency component 64 indicating the unnecessary reflected wave and a frequency component 65 indicating the multiple reflected wave appear (for the frequency change parts 423 and 433 of the signals 422 and 432, Since their frequency components are dispersive, these components 423 and 433 will be buried as a noise floor).

Regarding the frequency component 62 corresponding to the reflected wave 52 from the reference reflector 34, the position of the reference reflector 34 is fixed, and the propagation velocity of the microwaves in the storage tank 37 is within a range expected in advance. Since the center value of the frequency component is limited in advance, the range can be limited in advance. Therefore, the storage amount calculation unit 16 determines that the frequency component with a large level (62 in this case) in the limited frequency range (frequency range near Δf1) is limited in advance.
Is applicable), and the center frequency Δf1 is detected.

Next, the storage amount calculation unit 16 detects a frequency component having a high level in the range higher in frequency than Δf1, so that the frequency component 63 is the object of detection and its center frequency Δf2 is detected. ..

Since these frequencies Δf1 and Δf2 have a relationship of Δf1 / Δf2 = d11 / d12, and the distance d11 is known, the storage amount calculation unit 16 uses the above formula to calculate the storage amount from the antenna 11 to the oil surface.
The distance d12 to 361 is calculated, and the storage amount of oil 36 is calculated based on the calculation result. Then, the calculation result is displayed on the display 17
To display and display.

An embodiment of the invention described in claim 2 will be described below with reference to the drawings.

The electrical configuration of this embodiment is very similar to the block diagram shown in FIG. 1, so that the configuration will be described with reference to FIG.

Antenna 11, circulator 12, mixer 1
3, amplifier 14, frequency analysis unit 15, microwave oscillator 18,
The control signal generator 19 and the indicator 17 have the same configuration, and the only difference is the storage amount calculation unit 16, and the storage amount calculation unit 16 is a level that indicates the reflected wave from the surface of the stored material. The storage amount is calculated based on the frequency of the frequency component of.

Further, in the block diagram shown in FIG. 1, the frequency analysis unit 15 corresponds to the second frequency analysis unit described in claim 2, and the storage amount calculation unit 16 calculates the second storage amount calculated in claim 2. It corresponds to the department.

Regarding the reference reflector 34 shown in FIG.
In the invention of claim 1, the reflection is positively used as a reflector for indicating the reference position, but in the configuration of the invention of claim 2, the reference reflector 34 is not necessary. ..

However, in the following description, in order to make the description easy to understand, the reference reflector 34 will be described as follows.
It is indispensable as a part of the structure due to the strength of the oil tank, and it is impossible to remove it, and it corresponds to a part of the structure that causes unnecessary reflection.

From the above, the waveform of the frequency distribution shown in FIG. 4 is guided to the storage amount calculation unit 16, but at this time, the frequency component 62 indicating the reflected wave 52 from the reference reflector 34 is It becomes a frequency component showing unnecessary reflection.

On the other hand, the storage amount calculation unit 16 has a configuration in which the detection range of the frequency component is limited, and the detection range of the frequency component is the surface of the petroleum when the storage amount of the petroleum 36 is the maximum (see FIG. 2).
(Represented by 362) is limited to a frequency range higher than the frequency f3 corresponding to The frequency component below the frequency f3 is regarded as unnecessary reflection, and the frequency component is not detected.

Further, the storage amount calculation unit 16 performs an operation of determining that the frequency component having the maximum level is the reflected wave from the petroleum surface 361 in the frequency range of f3 or higher. ..

The electrical construction of one embodiment of the storage tank monitoring device according to the second aspect of the present invention is as described above, and its operation will be described below.

The storage amount calculation unit 16 to which the analysis result shown in FIG. 4 is given searches for the frequency component having the maximum level within the frequency range f3 or higher. It is determined that the frequency component 63 having the maximum level indicates the reflected wave from the oil surface 361, and the central frequency Δf2 of the frequency component 63 is detected by the storage amount calculation unit 16. And the detected frequency Δ
The distance d12 is calculated based on f2, and the storage amount of the oil 36 is calculated based on the calculation result.

The result of this calculation is guided to the display 17 and displayed. The value displayed at this time is the frequency component 62 of the reflected wave 52 from the reference reflector 34 that causes unnecessary reflection.
Despite its extremely high level, the storage volume corresponds exactly to the position of the oil surface 361.

The present invention is not limited to the above-mentioned embodiment, and the stored matter is applied to petroleum 36, but the present invention is also applied to other stored materials such as LPG and LNG. It is also possible to apply the same to a stored material such as powder.

The reference reflector 34 has been described as a flat ring provided in the vicinity of the end of the opening 321 of the antenna housing 32, but other shapes, such as a projection shape, may be used. In addition, a part of the structure (such as a beam) may be shared with the reference reflector.

The frequency analysis unit 15 has been described using the FFT analyzer. However, it is possible to use another spectrum analyzer or the like.

[0044]

According to the first aspect of the present invention, the reference reflector for reflecting the FM modulated microwave is provided in the storage tank, and the frequency component of the difference signal corresponding to the reflected wave is analyzed by the first frequency analysis unit. After that, based on the analysis result, the first storage amount calculation unit calculates the storage contents of the stored material by using the ratio of the frequencies of both the frequency component indicating the position of the reference reflector and the frequency component indicating the position of the reflection surface of the storage object. Since the storage amount is calculated, the parameter indicating the microwave propagation velocity is deleted in the calculation of the storage amount, so it is possible to eliminate the influence of changes in the microwave propagation velocity on the measured values. ing. In the invention according to claim 2, among the frequency components analyzed by the second frequency analysis unit, the second storage amount calculation unit identifies the frequency component indicating the reflection from the stored object based on the level, Since the storage amount of the stored material is calculated based on the frequency of the identified frequency component,
Since the unnecessary reflection is excluded from the calculation process, it is possible to remove the influence of the unnecessary reflected wave.

[Brief description of drawings]

FIG. 1 is a block diagram showing an electrical configuration of an embodiment of the present invention.

FIG. 2 is a schematic explanatory view showing the inside of an oil tank of one embodiment when the present invention is applied to a storage tank for storing oil.

FIG. 3 is an explanatory diagram showing a state of signals of a main part of the embodiment shown in FIG.

FIG. 4 is an explanatory diagram showing analysis results of frequency component distribution.

[Explanation of symbols]

 15 First or second frequency analysis unit 16 First or second storage amount calculation unit 37 Storage tank 41 FM modulated microwave 52, 54 Reflected wave 131 Difference signal

Claims (2)

[Claims] 1. F toward the stored material in the storage tank
The M modulated microwave is transmitted, and this FM modulated microwave
FM modulated microwave that is a transmission signal at a transmission / reception position
And reflected from the storage direction at the transmitting and receiving position
Difference showing difference from FM modulated microwave which is reflected wave
A storage device for detecting the storage amount of the storage product based on a signal
And a FM modulation microwave provided in the storage tank.
And a first reflector for analyzing the distribution of frequency components of the difference signal.
The wave number analysis unit and the frequency component analyzed by the first frequency analysis unit
The frequency component indicating the position of the reference reflector and the storage
Of both the frequency component and the frequency component indicating the position of the reflecting surface of the object
A first storage for calculating a storage amount of the storage based on a ratio.
Storage tank monitoring characterized by having a storage amount calculation unit
apparatus. 2. F toward the stored material in the storage tank
The M-modulated microwave is transmitted, and the difference between the FM-modulated microwave that is the transmission signal at the transmission / reception position of the FM-modulated microwave and the FM-modulation microwave that is the reflected wave reflected from the storage direction at the transmission / reception position is determined. In the storage tank monitoring device that detects the storage amount of the stored material based on the difference signal shown, the second frequency analysis unit that analyzes the distribution of the frequency components of the difference signal, and the second frequency analysis unit analyzes the distribution. A second storage amount calculation unit that calculates a storage amount of the stored material based on a frequency of a frequency component of a level indicating reflection from the stored material among the frequency components. Monitoring equipment.