JPH10142029A - Level gauge - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a high-accuracy level gauge which is reduced in cost and size by commonly using one waveguide as both transmitter- and receiver- side waveguides and attaching hole of which can be reduced in diameter and, at the same time, which can prevent the interference of the reflected waves of leakage microwaves. SOLUTION: A level gauge is provided with a microwave transmitter 10, a microwave receiver 11, and a guide member 14 which guides microwaves transmitted from the transmitter 10 to the receiver 11 and the gauge constituted so that the gauge can detect the contact of an object to be detected with the guide member 14 by protruding the member 14 into a storage container 15. The member 14 is composed of a single waveguide 18 and the transmitter 10 and receiver 11 are coupled with one end of the waveguide 18. At the same time, a guide body 19 which is made of a dielectric substance and provided with a microwave reflecting member 20 is connected to the other end of the waveguide 18.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a level meter mounted on a storage container for various liquids and powders to detect the storage amounts of the liquids and powders.

[0002]

2. Description of the Related Art Conventionally, a container for storing various liquids and granular materials has been provided with a level meter for detecting the amount of storage. The level meter is known to have various configurations and detection principles.
No. 33041 proposes a level meter using microwaves as a detection medium. The level meter includes a microwave transmitter, a microwave receiver, and a guide member for guiding microwaves emitted from the microwave transmitter to the microwave receiver, the guide comprising: A level meter attached to the storage container by projecting the member into the storage container, wherein the guide member is made of a dielectric material, and the guide member is formed by a difference between the dielectric constant of air and the dielectric constant of the detection target. The detection principle is based on the fact that the propagation amount of the microwave propagating in the inside changes.

That is, since the dielectric constant of the object to be detected is different from the dielectric constant of air, a part of the microwave propagating through the guide member is detected by the contact or immersion of the guide member with the object to be detected. The storage level of the object to be detected is detected by reducing the amount of microwaves leaking to the body side and reaching the microwave receiver. This level meter has various advantages such as being able to cope with substances that cannot be detected by light, ultrasonic waves, or the like because the microwave propagates through the guide member.

[0004]

By the way, in the above-mentioned level meter, the guide member has a transmitter side waveguide connected to the microwave transmitter side and a receiver connected to the microwave receiver side. The waveguide-side waveguide is connected with a guide made of a dielectric material. Therefore, two waveguides are required, and the waveguides must be arranged in parallel with a certain distance therebetween, and the mounting hole of the storage container is inevitably large. Also, since the guide body is U-shaped curved,
Depending on the use environment, a part of the microwave incident on the guide may pass through the guide and leak to the outside. The leaked microwave may be reflected by the object to be detected and re-enter the guide body to cause interference with the transmission wave from the microwave transmitter, thereby lowering the detection accuracy.

[0005] Therefore, the present invention shares the advantage of the principle of detection in the above-mentioned level meter, while sharing the waveguide on the transmitter side and the waveguide on the receiver side with one waveguide. To provide a high-precision level meter by reducing the cost, reducing the diameter of the mounting hole of the container, and further reducing the size of the entire device, and preventing interference by reflected waves of microwaves leaking from the guide body. It is the purpose.

[0006]

The above object is achieved by the following level meter according to the present invention. (1) a microwave transmitter, a microwave receiver, and a guide member for guiding microwaves emitted from the microwave transmitter to the microwave receiver; A level meter protruding into a storage container and detecting contact of an object to be detected with the guide member, wherein the guide member is formed of a single waveguide, and the microwave is provided at one end of the waveguide. A level meter, wherein a transmitter and a microwave receiver are connected, and a guide made of a dielectric having a microwave reflecting member is connected to the other end. (2) a microwave transmitter, a microwave receiver, and a guide member for guiding microwaves emitted from the microwave transmitter to the microwave receiver; A level meter protruding into a storage container and detecting contact of an object to be detected with the guide member, wherein the guide member is formed of a single waveguide, and the microwave is provided at one end of the waveguide. A transmitter and a microwave receiver are connected, and a guide made of a dielectric having a reflecting member having a polarization function of changing the direction of the electric field of the microwave is connected to the other end, and the microwave is connected. A level meter, wherein the wave receiver detects a microwave parallel to an electric field direction of the microwave polarized by the reflection means. (3) The guide according to the above (1) or (1), wherein the guide body includes a reflecting member that reflects the microwave emitted from the microwave transmitter at an arbitrary angle with respect to the center axis of the guide body. Level meter according to 2). (4) The guide according to (1) or (2), wherein the guide body has a portion protruding from the waveguide bent in a substantially J-shape, and a reflection member is provided on a distal end surface thereof. Level meter.

[0007]

Preferred embodiments of the present invention will be described below in detail with reference to the accompanying drawings. Note that common parts in the following embodiments are denoted by common reference numerals, and only different parts or functions newly added for each embodiment will be described using new reference numerals.

FIG. 1 is a partial sectional side view showing a first embodiment of the present invention. As shown, the level meter 10
Reference numeral 0 denotes a sealed housing 13 containing the microwave transmitter 10, the microwave receiver 11, and various circuit elements 12.
And a single linear guide member 14 protruding from the housing 13, and with the guide member 14 inserted through a mounting hole 15 a opened in the storage container 15, the bottom peripheral edge of the housing 13 is attached to the mounting hole 15 a. And a mounting member 16 for fixing the guide member 14 to the outer periphery of the object W. The lower end of the guide member 14 is opposed to the surface of the detection object W such as a liquid.

The microwave transmitter 10 is a device for generating microwaves, and for example, a known microwave oscillator such as a Gunn diode or an impatt diode can be used. The output of the microwave transmitter 10 does not require a large output because the microwave propagates only inside the guide member 14.

The microwave receiver 11 is a device for receiving the microwave transmitted from the microwave transmitter 10, and a known microwave receiver represented by a detection diode or the like can be used. Also, regarding its characteristics, it is not particularly necessary to have a low noise figure.

The circuit elements 12 are various electronic components mainly for driving and controlling the microwave transmitter 10 and the microwave receiver 11, mounted on a printed circuit board 17 and housed in a housing 13. . Although not shown, these circuit elements 12 are connected to an external power supply and an external control device through a cable or the like.

The guide member 14 comprises a single waveguide 18 having an upper end to which the microwave transmitter 10 and the microwave receiver 11 are connected, and a lower end connected to a guide 19 made of a dielectric material. You. The waveguide 18 is a corrosion-resistant hollow tube made of stainless steel or the like, and has a hollow interior filled with a dielectric 21 for preventing dew condensation. Also,
The waveguide 18 may be a straight tube or a tapered shape having a large diameter toward the lower end can increase the mechanical strength of the dielectric portion.

The guide body 19 has a rod shape, a part of which is exposed at a lower portion of the waveguide 18, and a reflector 20 made of metal is adhered to the tip. The tip is the guide 1
9 is a flat surface orthogonal to the axis, and the reflecting plate 20 is provided so as to cover the entire surface. Also, this guide body 19
It is preferable to use a low dielectric constant material because the range of the detectable dielectric constant of the detection target is widened. Further, it is preferable that the material has excellent chemical resistance and heat resistance. In consideration of these requirements, for example, it is preferable to be made of a fluororesin.

The reflection plate 20 preferably has corrosion resistance to the detection object W, and is preferably made of stainless steel.

FIG. 2 shows a circuit configuration including the above-described circuit elements 12 of the level meter having the above-described configuration, and FIG. 3 shows output waveforms of the respective sections. In FIG. 2, the microwave transmitter 1 is output at a predetermined period from the output stage of the oscillator driving circuit 22.
Drive 0 to generate microwaves. The transmitted microwave becomes a transmission wave M1, propagates through a waveguide (not shown), reaches a guide body 19, is reflected by a reflection plate 20, becomes a reflected wave M2, and becomes a guide body 19 and a guide member again. And reaches the microwave receiver 11. On the microwave receiver 11 side, the potential generated by the reception is output to the comparison circuit 25 via the amplification circuit 24, and the detection result is transmitted to a control device 26 connected to the comparison circuit 25 to an external control device (not shown) Transmit to device.

In such a configuration, the detected object W is not raised to the lower end of the guide member 19 (level L
In 0), the reflected wave M2 reaches the microwave receiver 11 without being attenuated. Therefore, the transmitted wave M1 and the reflected wave M2
"" Means a waveform having substantially the same amplitude and frequency as shown in FIGS. 3 (a) and 3 (b). However, if the level of the detection object W rises before the guide body 19 is immersed (level L
1) A part of the transmission wave M1 leaks to the detection target W side, and further leaks to the detection target W side after being reflected by the reflection plate 20. As a result, the reflected wave becomes a wave having a small amplitude as shown in FIG.
1 is received.

Here, in the guide member 14, the transmission wave M
Since both 1 and the reflected wave M2 (or M3) propagate, the microwave receiver 11 receives these mixed waves. Further, since the transmitted wave M1 and the reflected wave M2 (or M3) have the same frequency (phase), they interfere with each other and cause a so-called Doppler shift. Therefore, when the level of the detection target W is L0, the amplitude becomes the maximum value (P0) as a composite wave of the transmission wave M1 and the reflected wave M2 as shown in FIG. in case of,
The minimum value (P1) is obtained as shown in FIG. The comparison circuit 25 detects such a potential difference corresponding to the difference in the level of the detection target W, and generates an alarm output to the outside through the output circuit 26 based on the detection result.

In the above level detection, when the detection object W and the guide body 19 are not in contact (level L0),
The guide body 19 is rod-shaped, that is, a straight tube, and the transmission wave M
Since 1 is incident parallel to the axis of the guide 19, the leakage of the transmission wave M1 from the guide 19 is substantially zero.
Further, since the reflection plate 20 is formed on a flat surface orthogonal to the axis of the guide member 19, the transmission wave M 1 is inverted in the incident direction by the reflection plate 20 and propagates again parallel to the axis of the guide member 19. As described above, since both the transmission wave M1 and the reflected wave M1 propagate through the guide member 19 without leaking, the detection accuracy does not decrease due to the leaked microwave entering the guide member 19 again. Furthermore, even if there is a leak, the reflected wave from the detection target W can be blocked by the reflection plate 20, and the influence of the reflected wave by the leaked microwave can be minimized. When the guide body 19 is immersed in the detected object W (level L1), both the transmission wave M1 and the reflected wave M2 leak into the detected object W, and when the level L0 is set. And the difference in the leakage ratio increases. As a result, S / N is improved and detection accuracy is improved. The same can be said for the level meter described in Japanese Patent Application Laid-Open No. 7-33041 by the present applicant. That is, since the level meter has a configuration in which only the transmission wave propagates in the guide, only the transmission wave leaks when the guide is immersed in the detection target. On the other hand, in the present invention, since both the transmission wave M1 and the reflected wave M2 leak, the amount of leakage as a whole increases, which is advantageous in S / N and detection accuracy.

In the above description, the guide member 1
Assuming that the length of the tube 4 (the length of the waveguide 18 + the length of the protrusion of the guide body 19) is m and the wavelength of the microwave is λ, (2 m
/ Λ = n), and it is known that interference occurs most effectively when the value of n is a positive integer. However, actually, the pipe length m of the guide member 14 is predetermined according to the detection level of the detection target W in the storage container 15, and the frequency λ of the microwave also changes according to the ambient temperature. N is not always an integer. Therefore, in FIG. 2, the output of the oscillator driving circuit 22 is periodically changed by the varactor diode 23 to change the applied voltage V, as shown in FIG. The microwave receiver 11 can sample a composite wave indicating the peak voltage P from the composite waves continuously received, and can perform level detection using the frequency f _{0 of the} composite wave according to the principle described above.

FIG. 5 shows a second embodiment of the present invention. In addition, the left side of the figure shows the cross section of the main part of the guide body 19 in the first embodiment, and the right side shows the cross section of the main part of the guide body 30 in the second embodiment for comparison. . That is, in the first embodiment, the guide body 19
Has a flat surface that intersects with the central axis by 90 °, and a reflecting plate 20 is provided on this surface. On the other hand, the distal end surface of the guide body 30 in the second embodiment has a shape that reflects the transmission wave M1 at an arbitrary angle with respect to the center axis of the guide body 30. For example, as shown in the figure, an inclined surface intersecting at an angle (θ) with the central axis of the guide body 30 may be provided, and the reflecting plate 20 may be provided on this surface. Although not shown, the microwave transmitter 1
The reflecting plate 20 may be provided on a hemispherical surface or a pyramid surface having the zero side as a vertex.

In such a configuration, when the medium surrounding the guide members 19 and 30 is air, that is, when the medium surrounding the guide members 19 and 30 is not in contact with the detection target W (level L0), as shown in FIG. The attenuation ratio of the reflected wave M2 to the transmitted wave M1 is substantially the same for both the guides 19 and 30. However, as shown in FIG. 3B, when the level of the detected object W rises so as to surround the guide members 19 and 30 (L1),
In both cases, the microwave leaks to the detection target W side, but the leakage amount (r2) from the guide body 30 including the inclined reflector 20 is smaller than the leakage amount (r1) from the guide body 19 including the flat reflector 20. ) Increases. As a result, the ratio between the transmitted wave M1 and the reflected wave M3 increases, and thus the S / N ratio increases and the detection sensitivity increases. The amount of leakage can be adjusted by the inclination angle (θ).

FIG. 6 shows a guide body 40 according to the third embodiment. As shown, the guide body 40
Is formed such that a protruding portion from the waveguide 18 is bent into a substantially J shape,
The reflective member 20 is provided on the tip surface.
As a result, the level of the detection target W increases, and the guide 4
When 0 is immersed, the contact area with the detection target W becomes larger than that of the rod-shaped guides 19 and 30, and the amount of microwave leakage increases, so that the S / N ratio can be increased.

FIG. 7 shows a circuit configuration according to a fourth embodiment of the present invention. As shown, a circulator 50 is interposed between the microwave transmitter 10 and the microwave receiver 11. The circulator 50 regulates the direction of propagation of the microwave, and thereby only the reflected wave M2 (or M3) is transmitted to the microwave receiver 1
1 can be sent. Therefore, there is no interference between the transmission wave M1 and the reflection wave M2 as in the first embodiment,
It is not necessary to adjust the wavelength of the microwave. The configuration of the guide body and the principle of detecting the detection target W are as described above.

FIG. 8 shows a fifth embodiment of the present invention. As shown in the figure, a microwave A1 having an electric field direction (for example, x direction) parallel to the applied current direction is transmitted from the wave transmitting surface 60a of the microwave transmitter 60. The microwave A1 propagates through a waveguide (not shown) as a transmission wave, reaches the guide body 19, and is reflected by the reflection member 62. Here, a plurality of conducting wires 62a are arranged on the reflecting member 62 at predetermined intervals so as to intersect with the electric field direction (x) of the microwave A1 at a predetermined angle.
When the microwave A1 is reflected by the reflecting member 62, its electric field direction (x) is deflected by 90 °. Then, the reflected wave becomes a microwave A2 having an electric field direction (y) orthogonal to the electric field direction (x) of the microwave A1, and the guide body 1
9. The light propagates through the waveguide to the microwave receiver 61.

On the other hand, the receiving surface 61 of the microwave receiver 61
For a, the detection plane is adjusted in a direction orthogonal to the direction of the current applied to the wave transmitting surface 60a of the microwave transmitter 60, that is, in a direction parallel to the electric field direction (y) of the microwave A2.
Therefore, the microwave receiver 61 is configured to detect only the microwave A2, so that the transmitted wave and the received wave can be distinguished in the direction of the electric field. According to this embodiment, only the received wave is received by the microwave receiving surface 60a of the microwave transmitter 60, the receiving surface 61a of the microwave receiver 61, and the conductor 62a of the reflecting member 62 only. Since the circulator 50 is detected by the wave device 61, the circulator 50 is not required, and the circuit configuration is simplified. Incidentally, the reflecting means 62 is provided with the inclined guide body 3 as shown in FIG.
0, or a J-shaped guide body 40 as shown in FIG. 6, and a conductive wire 62a may be provided on each surface. The detection principle of the detection target W is as described above.

[0026]

As is apparent from the above description, in the level meter according to the present invention, the number of components can be reduced by sharing the guide member between the microwave transmitter side and the receiver side. Thus, the diameter of the mounting hole can be reduced. Further, it is possible to prevent the detection accuracy from being lowered due to the reflected microwave from the guide body being reflected by the detection body.

[Brief description of the drawings]

FIG. 1 is a partial cross-sectional side view of a level meter according to a first embodiment of the present invention.

FIG. 2 is a block diagram showing a circuit configuration of the level meter shown in FIG.

FIG. 3 is a waveform diagram of a transmission wave, a reception wave, and a composite wave in the level meter shown in FIG.

FIG. 4 is a waveform chart showing peak voltages of an output waveform and a composite waveform when a varactor diode is used in the level meter according to the first embodiment of the present invention.

FIG. 5 is an enlarged sectional view of a main part showing a second embodiment of the present invention in comparison with the first embodiment.

FIG. 6 is an enlarged sectional view of a main part of a guide body according to a third embodiment of the present invention.

FIG. 7 is a block diagram showing a circuit configuration according to a fourth embodiment of the present invention.

FIG. 8 is an explanatory diagram of a geometric arrangement structure according to a fifth embodiment of the present invention.

[Explanation of symbols]

 100 Level meter 10, 60 Microwave transmitter 11, 61 Microwave receiver 12 Circuit element 13 Hermetic housing 14 Guide member 15 Storage container 15a Mounting hole 18 Waveguide 19, 30, 40 Guide body 20, 62 Reflection Plate 22 Oscillator amplifier circuit 23 Varactor diode 25 Comparison circuit 50 Circulator

Claims (4)

[Claims] A microwave transmitter; a microwave receiver; and a guide member for guiding microwaves emitted from the microwave transmitter to the microwave receiver. A level meter for projecting a member into a storage container and detecting contact of the detection target with the guide member, wherein the guide member is formed of a single waveguide, and the guide member is provided at one end of the waveguide. A level meter, wherein a microwave transmitter and a microwave receiver are connected, and a guide made of a dielectric having a microwave reflecting member is connected to the other end. 2. The apparatus according to claim 1, further comprising: a microwave transmitter, a microwave receiver, and a guide member for guiding microwaves emitted from the microwave transmitter to the microwave receiver. A level meter for projecting a member into a storage container and detecting contact of the detection target with the guide member, wherein the guide member is formed of a single waveguide, and the guide member is provided at one end of the waveguide. A microwave transmitter and a microwave receiver are connected, and a guide body made of a dielectric material having a reflection member having a polarization function of changing the electric field direction of the microwave is connected to the other end, and The said microwave receiver detects the microwave parallel to the electric field direction of the microwave polarized by the said reflection means, The level meter characterized by the above-mentioned. 3. The guide member according to claim 1, wherein the guide member includes a reflecting member that reflects the microwave emitted from the microwave transmitter at an arbitrary angle with respect to a center axis of the guide member. 2. The level meter according to 2. 4. The level according to claim 1, wherein the guide body has a portion protruding from the waveguide bent substantially in a J-shape, and a reflection member is provided on a tip end surface of the guide body. Total.