GB2393872A - Water leakage detector - Google Patents
Water leakage detector Download PDFInfo
- Publication number
- GB2393872A GB2393872A GB0329045A GB0329045A GB2393872A GB 2393872 A GB2393872 A GB 2393872A GB 0329045 A GB0329045 A GB 0329045A GB 0329045 A GB0329045 A GB 0329045A GB 2393872 A GB2393872 A GB 2393872A
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- water leakage
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01M—TESTING STATIC OR DYNAMIC BALANCE OF MACHINES OR STRUCTURES; TESTING OF STRUCTURES OR APPARATUS, NOT OTHERWISE PROVIDED FOR
- G01M3/00—Investigating fluid-tightness of structures
- G01M3/02—Investigating fluid-tightness of structures by using fluid or vacuum
- G01M3/04—Investigating fluid-tightness of structures by using fluid or vacuum by detecting the presence of fluid at the leakage point
- G01M3/16—Investigating fluid-tightness of structures by using fluid or vacuum by detecting the presence of fluid at the leakage point using electric detection means
- G01M3/18—Investigating fluid-tightness of structures by using fluid or vacuum by detecting the presence of fluid at the leakage point using electric detection means for pipes, cables or tubes; for pipe joints or seals; for valves; for welds; for containers, e.g. radiators
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S13/00—Systems using the reflection or reradiation of radio waves, e.g. radar systems; Analogous systems using reflection or reradiation of waves whose nature or wavelength is irrelevant or unspecified
- G01S13/02—Systems using reflection of radio waves, e.g. primary radar systems; Analogous systems
- G01S13/04—Systems determining presence of a target
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S13/00—Systems using the reflection or reradiation of radio waves, e.g. radar systems; Analogous systems using reflection or reradiation of waves whose nature or wavelength is irrelevant or unspecified
- G01S13/02—Systems using reflection of radio waves, e.g. primary radar systems; Analogous systems
- G01S13/50—Systems of measurement based on relative movement of target
- G01S13/52—Discriminating between fixed and moving objects or between objects moving at different speeds
- G01S13/56—Discriminating between fixed and moving objects or between objects moving at different speeds for presence detection
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01V—GEOPHYSICS; GRAVITATIONAL MEASUREMENTS; DETECTING MASSES OR OBJECTS; TAGS
- G01V9/00—Prospecting or detecting by methods not provided for in groups G01V1/00 - G01V8/00
- G01V9/02—Determining existence or flow of underground water
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- Engineering & Computer Science (AREA)
- Radar, Positioning & Navigation (AREA)
- Remote Sensing (AREA)
- Physics & Mathematics (AREA)
- General Physics & Mathematics (AREA)
- Computer Networks & Wireless Communication (AREA)
- Life Sciences & Earth Sciences (AREA)
- Hydrology & Water Resources (AREA)
- General Life Sciences & Earth Sciences (AREA)
- Geophysics (AREA)
- Geophysics And Detection Of Objects (AREA)
- Examining Or Testing Airtightness (AREA)
Abstract
A water leakage detector is disclosed for detecting the existence of a water leak from an underground pipe. The detector comprises a transmitting antenna 12 for radiating into the ground a signal composed of an electromagnetic wave and a receiving antenna 14 for receiving a reflected wave of the transmitted signal. The received signal is passed to a demodulator 20 along with a reference signal from a reference signal generator 24, having the same frequency as that of the transmitted signal. A demodulation signal is output from these signals according to a phase shift relative to the transmitted signal. A bandpass filter 84 passes through the component of the demodulation signal corresponding to a Doppler frequency caused by a flow in a leaking section of the pipe to an amplifier 86. An output of the amplifier 86 may be provided to a display device or a storage device which may be used to judge if a water leak exists.
Description
GB 2393872 A continuation (72) cont Hideyuki Fujita Takuya Tasaki Shunji
Tananmura Fujio Oka (74) Agent and/or Address for Service: Mewburn Ellis York House, 23 Kingsway, LONDON, WC2B 6HP, United Kingdom
DESCRIPTION
WATER LEAKAGE DETECTOR AND ANTENNA THEREOF
Technical Field
The present invention relates to a water leakage detector for detecting the existence and non-existence of water leakage from piping laid underground using an electromagnetic wave and, more particularly, is lo concerned with an antenna for a water leakage detector and a water leakage detector suitable for detecting water leakage making use of Doppler effect caused by a flow in a water leakage part.
Background Art
15 Conventionally, when the detection of water leakage from a water pipe laid underground is performed, a sound of water leaking from the water pipe is caught by a microphone pressed on a ground surface, which amplifies the sound. As the method of catching a sound of leaking water by a microphone, however, requires skill in judging the existence or nonexistence 20 of water leakage, a noise and a vibration caused by a vehicle moving on a road become an obstacle, and so on, detection accuracy is not always high.
Herein, the applicant of the present invention developed a device (Japanese Patent Laid-open No. Hei 9-5200) for detecting the existence and non-
existence of water leakage from a water pipe in the ground by radiating an 25 electromagnetic wave of a single frequency into the ground, receiving its reflected wave, and in the received reflected wave detecting a Doppler
frequency caused by a flow in a water leakage part. FIG. 9 is a block diagram showing one example of a conventional water leakage detector utilizing an electromagnetic wave.
In FIG. 9, a water leakage detector 10 comprises a transmitting 5 antenna 12 and a receiving antenna 14. The transmitting antenna 12, which is connected to a signal generator 16 comprising an oscillator and so on, for generating a high frequency transmitted signal, radiates in the ground the transmitted signal of an electromagnetic wave outputted from the signal generator 16.
10 Meanwhile, the receiving antenna 14 receives a reflected wave of the transmitted signal radiated from the transmitting antenna 12. To the receiving antenna 14, a high frequency amplifier (RF- amplifier) 18 for amplifying a reflected signal, which is the received reflected wave, is connected. To an output side of the RF amplifier 18, a demodulator 20 for 15 inputting an output signal from the RF amplifier 18 as a received signal is connected. To the demodulator 20, a reference signal, which a reference signal generator 24 outputs via a phase shifter 22, is also inputted. The reference signal generator 24, which is connected to the signal generator 16, partially inputs the transmitted signal outputted from the signal generator 16, 20 and outputs a signal of the same frequency as that of the transmitted signal to the phase shifter 22 as a reference signal.
The demodulator 20 mixes the reflected signal (the received signal) received by the receiving antenna 14 with the reference signal inputted via the phase shifter 22, and removes a component of the transmitted signal (a 2s signal component with the same phase as that of the transmitted signal) from the received signal. The demodulator 20 then outputs to a low-pass filter 26
and an amplifier 28 a demodulation signal (an intermediate frequency (IF) signal) according to a phase shift relative to the transmitted signal. The low-
pass filter 26 passes therethrough a signal component from a fixed matter (a fixed phase shift component relative to the transmitted signal, or a direct s current component) such as a buried pipe and a cavity in the ground and outputs it to an oscilloscope 30 for displaying it. Meanwhile the amplifier 28 amplifies and outputs the demodulation signal outputted from the demodulator 20. An operator, which is not shown, then adjusts an output of the phase shifter 22 via a dial of the phase shifter 22 so that the signal 10 component in the output signal from the demodulator 20 reflected from the fixed matter such as a pipe laid underground and a cavity is made zero, in other words, an output from the low-pass filter 26 is made zero.
In short, in the detection of water leakage from a pipe laid underground by radiating an electromagnetic wave in the ground, removed 15 are a combined signal between the transmitting and receiving antennas (an electromagnetic wave 34 reflected from a ground surface 32, which directly enters the receiving antenna 14 from the transmitting antenna 12, and an electromagnetic wave 38, which enters directly to the receiving antenna 14 through an underground 36, as shown in FIG. 10) and a fixed reflected signal 20 whose phase does not change coming from an underground buried matter such as an artificial object existing in the underground 36 like piping 40 and an object existing in the nature like a cavity 42 formed in the underground 36, a rock and stone, and a transformed part of a stratum (a soil), which are not shown. As a result, the demodulator 20 outputs only a signal based on a 2s Doppler frequency caused by a flow in a water leakage part 44, and the signal is amplified by the amplifier 28.
As described above, the water leakage detector 10 detects with the use of an electromagnetic wave a Doppler frequency caused by Doppler effect from the water leakage part 44, so that it can detect if the water pipe laid underground is leaking or not without being influenced by the degree of an s operator's skill or a vehicle moving on a road.
In the conventional water leakage detector 10 using an electromagnetic wave as described above, however, since an ordinary antenna for underground buried matter probing radar is used for the transmitting antenna 12 and the receiving antenna 14, sufficient detection 10 accuracy could not be obtained. To be more concrete, the antenna for the conventional water leakage detector 10 is shown in FIG. 11.
The antenna 46 is an antenna for underground probing radar, wherein an antenna element 48 is shaped to be a so-called bow-tie antenna and an antenna box 50 made of metal is provided covering one side face of the 15 antenna element 48. A width a, a length b and a height c of the antenna box 50 are usually determined based on a center frequency of a sweep frequency.
Inside the antenna box 50 an electric wave absorbent 52 made of, for example, ferrite or carbon urethane is disposed. The electric wave absorbent 52 levels an amplitude characteristic relative to a frequency as well as preventing 20 multiple reflections inside the antenna box 50. As a result, in the antenna 46 for underground buried mater probe, an antenna gain relative to a frequency (a frequency characteristic) is broadband as shown in FIG. 12.
This is because in the underground probing radar, a frequency is swept up to about several tens of MHz to about 1 GHz, a phase change of the 25 reflected signal from a fixed foreign matter in the ground (an artificial object such as piping and a natural object such as a cavity and a change of a
stratum) is artificially caused, and by analyzing the phase change, the foreign matter in the ground is detected and a distance from the foreign matter to the ground surface is obtained. Therefore, the conventional antenna 46, as shown in FIG. 12, can transmit and receive at a comparatively steady level an s electromagnetic wave superior in a broadband characteristic and of a broad frequency band. The conventional antenna 46, however, has to sacrifice a gain as it responds to a broadband electromagnetic wave. Therefore, the conventional antenna 46 is not suitable for an antenna for a water leakage detector detecting a Doppler frequency by radiating in the ground an 10 electromagnetic wave of a specific single frequency, which prevents detection accuracy from being enhanced.
Specifically, if the antenna 46 is used as the transmitting antenna 12, it cannot radiate an electromagnetic wave with sufficient strength when radiating an electromagnetic wave of a specific frequency. Meanwhile, if the 15 antenna 46 is used as the receiving antenna 14, it receives various kinds of noises of frequencies other than a specific frequency since it receives a broadband electromagnetic wave, so that extracting a faint reflected signal from the water leakage part is not easy.
In addition, in the conventional water leakage detector 10 for 20 detecting a Doppler frequency, an operator adjusts the dial of the phase shifter 22 to remove the fixed reflected signal (the direct-current signal component) from the IF signal outputted from the demodulator 20 as described above. As a result, the following disadvantages exist.
(1) A voltage comparator and the phase shifter 22 are required, which 25 complicates its circuit. (2) The phase shifter 22 needs to be adjusted each time the installation condition of the antenna changes. (3) As the
characteristics of an oscillation frequency (a frequency of the transmitted signal) and the phase shifter 22 drift depending on temperature, fine adjustment is required according to the time lapse. (4) Thereby, the combined signal between the antennas and a strong directcurrent signal s component, such as the reflected signal and so on from a fixed matter such as an underground buried matter cannot be removed sufficiently. In addition, an output of the amplifier 28 is saturated if an amplification factor of the amplifier 28 is magnified in order to catch a faint water leakage signal, therefore the amplification factor cannot be magnified and an S/N ratio 10 cannot be increased.
Disclosure of the Invention
The present invention is made to solve the above-mentioned disadvantages of a conventional art, and its object is to facilitate the detection 15 of a faint Doppler frequency caused in a water leakage part and to enhance the accuracy of detecting water leakage.
In addition, another object of the present invention is to simplify its circuit and to improve opera/ability.
In order to achieve the above-mentioned objects, an antenna for a 20 water leakage detector according to the present invention is an antenna for a water leakage detector for detecting the existence and non- existence of water leakage from a pipe laid in the ground by radiating an electromagnetic wave in the ground, receiving a reflected wave thereof and detecting a Doppler frequency, and it is so structured to have a planar dipole antenna element 2s with its width and length formed to be one half a wavelength of the above-
mentioned electromagnetic wave radiated in the ground, and a frame box
covering one side face of the antenna element to form a resonant cavity.
The antenna for the water leakage detector according to the present invention structured as above is a so-called half-wave antenna with the dimensions of the length and the width of the planar dipole antenna element s made to be one half a wavelength ( A) of the electromagnetic wave radiated in the ground, and the frame box is formed to be a cavity resonance type. As a result, the antenna of the present invention can obtain a big resonance characteristic and increase a gain for a frequency f corresponding to a specific wavelength A. Therefore, the antenna according to the present 10 invention, when used as a transmitting antenna, can radiate a strong electromagnetic wave of a specific frequency and, when used as a receiving antenna, can receive a reflected wave with small amount of noise, and as a result, the antenna of the present invention can facilitate the detection of a Doppler frequency and improve the detection accuracy of water leakage from 15 a water pipe laid underground.
Note that it is preferable that the antenna has a dielectric resonator provided to a transmission path of the planar dipole antenna element. By having the dielectric resonator made of, for example, ceramics provided to the transmission path, which is connected to the antenna element, the antenna 20 can increase a Q value showing the sharpness of resonance. Therefore, the antenna having the dielectric resonator can make a transmitted signal narrow band since the resonance characteristic in a desired frequency is improved, and can further lower the influence of a coming noise while improving a gain of transmitting and receiving.
25 In the water leakage detector comprising a transmitting antenna for radiating in the ground a transmitted signal composed of an electromagnetic
wave, and a receiving antenna for receiving a reflected wave of the transmitted signal radiated from the transmitting antenna, for detecting the existence and non-existence of water leakage from an underground buried pipe based on the reflected wave received by the receiving antenna, the s water leakage detector according to the present invention is so structured to have a demodulator which inputs from a reference signal generator a reference signal of the same frequency as that of the transmitted signal radiated from the transmitting antenna while inputting a received signal from the receiving antenna, for outputting a demodulation signal from these lo signals according to a phase shift relative to the transmitted signal; and a bandpass filter for passing therethrough a component in the demodulation signal corresponding to a Doppler frequency caused by a flow in a water leakage part.
The water leakage detector according to the present invention 5 structured as above can perform the detection of a Doppler frequency easily and without mistake by having the bandpass filter provided to an output side of the demodulator for passing therethrough a component in the demodulation signal outputted from the demodulator corresponding to a Doppler frequency caused by Doppler effect due to a flow in a water leakage 20 part. Furthermore, the water leakage detector of the present invention does not require a phase of the reference signal given to the demodulator to be adjusted by a phase shifter as conventionally required to simplify its circuit since a voltage comparator and a phase shifter are not needed. As the water leakage detector according to the present invention, in addition, does not 2s require the adjustment of the phase of the reference signal, water leakage detecting operation can be performed immediately in a place in which the
device is carried even when the installation condition of the antenna is changed and a transmission frequency drifts due to a temperature change, so that it becomes maintenance-free to thereby improve operatability drastically.
In addition, the water leakage detector of the present invention can increase s an amplification factor at the final stage of amplifying the signal passing through the bandpass filter, thereby enabling an S/N ratio to be increased.
Incidentally, the bandpass filter with a band frequency of 0.5 Hz to 1 kHz can be used. As the attenuation of the electromagnetic wave in the ground is big when the detection of water leakage from piping existing in the 10 ground is performed, a frequency used (a frequency of the transmitted signal) is usually lower than that of radar for aerial probe. Since a velocity of water and soil and movement in the water leakage part is also low, a Doppler frequency also becomes low. Therefore, a band frequency of the bandpass filter may be 0.5 Hz or more and 1 kHz or less, preferably from 0.5 Hz to 100 15 Hz. Brief Description of Drawings
FIG. 1 is an explanatory view of an antenna for a water leakage detector according to an embodiment of the present invention; 20 FIG. 2 is a plan view of an antenna element according to the embodiment; FIG. 3 is a frequency characteristic chart of a gain of the antenna according to the embodiment; FIG. 4 is an explanatory view of a principal portion of an antenna 2s according to another embodiment; FIG. S is a frequency characteristic chart of a gain of the antenna
according to another embodiment; FIG. 6 is a block diagram of the water leakage detector according to the embodiment of the present invention; FIG. 7 is a chart showing a result of analyzing a frequency of a 5 reflected signal from a water leakage part detected by the water leakage detector according to the embodiment; FIG. 8 is a chart showing the correlation of a Doppler frequency to an operating frequency of the water leakage detector; FIG. 9 is a block diagram of a conventional water leakage detector.
lo FIG. 10 is an explanatory view of a principle for detecting a water leakage utilizing an electromagnetic wave; FIG. 11 is a perspective view of an antenna used for the conventional water leakage detector; and FIG. 12 is a frequency characteristic chart of a gain of the antenna for 15 the conventional water leakage detector.
Best Mode for Carrying out the Invention
Preferred embodiments of an antenna for a water leakage detector and a water leakage detector according to the present invention will be described 20 in detail referring to the attached drawings. Note that the same reference numerals will be used to designate the components corresponding to those described in the above-mentioned conventional art and the description
thereof will be omitted.
FIG. 1 is an explanatory view of the antenna for the water leakage 25 detector according to the embodiment of the present invention, and FIG. 2 is a plan view of an antenna element according to the embodiment.
In these drawings, an antenna 60 has an antenna box 62, which is frame box made of metal, wherein an antenna element 64 is provided on a bottom face of the antenna box 62. The antenna 60 is a so-called bow-tie antenna, wherein the antenna element 64 is a planar dipole antenna element s with one of the apex portions of a pair of triangle-shaped element chips 64a and 64b disposed to face with each other as shown in FIG. 2. Furthermore, the antenna element 64 constitutes a so-called half-wave dipole antenna with a dimension of a width d in a vertical direction in FIG. 2 and a dimension of a length e in a direction from the element chip 64a to 64b being-A /2, one half 10 wavelength A of an electromagnetic wave radiated in the ground.
Meanwhile, the antenna box 62 is so structured that the dimensions of two sides I and m of the bottom face are made to be (A /2) + lo, the value obtained by adding a fixing margin for fixing the antenna element 64 to A /2, or one half a wavelength A. The antenna box 62 is also so structured that Is a height h is made to be A /4, A /2 or A, its integral and multiple. Therefore, the antenna box 62 is formed to be a so-called cavity resonance type with A /2 as its basic dimension, and has a resonant cavity formed therein.
The antenna 60 as structured above is resonant at a predetermined Frequency f0 = c/ A O (c is a velocity of light), and a Frequency characteristic, 20 or an antenna gain for a frequency, as shown in FIG. 3, depicts a Gaussian curve of a resonant frequency fO as its center. Therefore, radiating a transmitted signal of the resonant frequency fO from a transmitting antenna composed of the antenna 60 enables a big antenna gain to be obtained so that a strong electromagnetic wave can be radiated in the ground. Furthermore, a 25 receiving antenna composed of the antenna 60 selectively receives a reflected signal of the resonant frequency fO so that it can receive a reflected signal
with less noise. Consequently, the water leakage detector using the antenna 60 as its transmitting antenna and receiving antenna can detect a Doppler frequency caused by water leakage from a water pipe laid underground without mistake and can improve detection accuracy of water leakage. In 5 addition, since the antenna 60 according to the embodiment does not require an amplitude characteristic to be leveled and does not require an electric wave absorbent to be provided inside the antenna box 62, it can reduce cost.
FIG. 4 is an explanatory view of a principal portion of an antenna according to another embodiment. In FIG. 4, a dielectric resonator 68 made 10 of, for example, ceramics is provided to a coaxial cable 66, which is a transmission path, inside an antenna box 62, which is not shown in the drawing. And to a tip of the coaxial cable 66 a baton 70, which is a transformer for performing impedance conversion, is connected. Each end of the balun 70 is connected to each of element chips 64a and 64b of an antenna 15 element 64.
In the antenna in the embodiment as structured above, since the dielectric resonator 68 is provided to the coaxial cable 66, a Q value showing the sharpness of resonance can be increased as in FIG. 5 showing a frequency characteristic. Therefore, the antenna in the embodiment can be resonant at a 20 desired frequency to make a transmitted signal narrow- band, so that the influence by a noise such as an electric wave of television and an electric wave of a portable telephone reaching the receiving antenna can be reduced, and a gain of transmitting and receiving can be improved, thereby further enhancing detection accuracy of water leakage.
2s FIG. 6 is a block diagram of the water leakage detector according to the embodiment of the present invention. In FIG. 6, the water leakage
detector 80 does not have a phase shifter and a reference signal generator 24 is connected directly to a demodulator 20. Thus, in the water leakage detector 80 a reference signal of the same frequency as that of the transmitted signal outputted from a signal generator 16 is inputted directly to the s demodulator 20 from the reference signal generator 24 without undergoing phase adjustment. To an output side of the demodulator 20 a low-noise preamplifier 82 is connected. To an output side of the preamplifier 82 a bandpass filter 84 is provided. The bandpass filter 84 in the embodiment is a so-called active filter using an operational amplifier. The bandpass filter 84 lo passes therethrough a component in a demodulation signal (IF signal) outputted from the demodulator 20, which corresponds to a Doppler frequency caused by a movement of water or a mixture of water and soil in a water leakage part in the ground. A band frequency of the bandpass filter 84 in the embodiment is *om 0.5 kHz to 1 kHz. To an output side of the 15 bandpass filter 84, in addition, an amplifier 86 is connected to amplify the signal which passes through the bandpass filter 84. An output of the amplifier 86 is outputted to a water leakage discriminator, a display device, a display instrument such as a meter, a recording device, which are not shown, and so on, and is used to judge if water leakage exists or not.
20 In the water leakage detector 80 in the embodiment as structured above, the signal generator 16 generates and outputs the transmitted signal, which is partially radiated in the ground via the transmission antenna 12 and partially given to the reference signal generator 24. The transmitted signal radiated from the transmitting antenna 12 is reflected from a foreign matter 25 such as piping and a cavity existing in the ground and a water leakage part of underground piping to reach the receiving antenna 14 as a reflected signal.
The reflected signal (a reflected wave) received by the receiving antenna 14 is amplified approximately 104 times by an RF amplifier 18 and inputted to the demodulator 20 as a received signal.
Meanwhile, the reference signal generator 24 inputs the signal 5 inputted from the signal generator 16 as the reference signal, that is, a reference signal of the same frequency as that of the transmitted signal, to the demodulator 20. The demodulator 20 mixes the inputted received signal with the reference signal and removes a signal component with the same phase as that of the transmitted signal. Then the demodulator 20 inputs to the 10 bandpass filter 84 via the preamplifier 82 an IF signal with a different phase from that of the transmitted signal as a demodulation signal. The bandpass filter 84 removes a direct-current signal component and various kinds of high-frequency noises caused by the reflection from piping, a cavity and so on in the ground. Then, the bandpass filter 84 passes theretrough a frequency 5 showing a phenomenon peculiar to water leakage. Specifically, the bandpass filter 84 passes therethrough and outputs only a signal component from 0.5 Hz to 1 kHz corresponding to a frequency corresponding to a Doppler frequency caused by a flow of water (or a mixture of water and soil) in a water leakage part. Then, the signal passing through the bandpass filter 84 is 20 amplified approximately 104 times by the amplifier 86, and transmitted to the display instrument after being changed to a voltage at a display level (several volts). In the embodiment, as described above, the reference signal is given to the demodulator 20 with the phase of the reference signal not adjusted by a 2s phase shifter. Also, the water leakage detector 80 has the bandpass filter 84 provided to the output side of the demodulator 20 to pass therethrough a
component in the demodulation signal outputted from the demodulator 2O, which corresponds to a Doppler frequency caused by water leakage. Thus, the water leakage detector 80 can detect a Doppler frequency caused by water leakage easily and without mistake, and judge with high accuracy if there is s water leakage or not from a water pipe laid underground.
In addition, as the water leakage detector 80 does not require a phase of the reference signal given to the demodulator 20 to be adjusted by a phase shifter, as is conventionally required, it does not need a voltage comparator and a phase shifter, thereby simplifying its circuit. As the water leakage 10 detector 80, furthermore, does not require the phase of the reference signal to be adjusted, it can immediately perform water leakage detecting operation in a place which the water leakage detector 80 is carried in, even when the installation condition of the antennas 12 and 14 is changed and a transmission frequency of the transmitted signal outputted from the signal 15 generator 16 drifts due to temperature change, so that it becomes maintenance-free, thereby improving operatability drastically. Furthermore, the water leakage detector 80 in the embodiment can increase an amplitude factor of the amplifier 86 for amplifying a signal which passes through the bandpass filter 84, so that an S/N ratio can be increased.
20 Incidentally, by using the above-mentioned antenna 64 in the embodiment as the transmitting antenna 12 and the receiving antenna 14, the water leakage detector 80 can enhance the accuracy of detecting water leakage. 2s Examples of Carrying out the Invention A water pipe was laid 1.2 m deep in the ground at a test place, which
was filled back again according to construction specifications for specified
asphalt paving. Then, after asphalt paving was performed, an experiment for detecting water leakage, which was made to cause five liters per minute from the water pipe laid underground, was carried out using a water leakage s detector 80 according to the embodiment. When water leakage detection was performed with an operating frequency of the water leakage detector 80, that is, a frequency of a transmitted- signal outputted from a reference signal generator 16, set at 400 MHz, water leakage could be detected with ease.
FIG. 7 shows the result of analyzing a frequency of a reflected signal 10 from a water leakage part at this time. In FIG. 7, a horizontal axis shows a frequency (a Doppler frequency) (Hz as its unit) of a signal passing through a bandpass filter 84, and a vertical axis shows signal amplitude (mV as its unit) of a gauge. As seen apparent from the chart, 10 Hz or less is a main component in a Doppler frequency included in the reflected signal from the 15 water leakage part, when an operating frequency is 400 MHz. In a Doppler frequency in the embodiment, it is apparent that a component from 2 Hz to 5 Hz is especially distinguished. It is also apparent from the result that a velocity of a movement (a flow) of water (or a mixture of water and soil) in the water leakage part is approximately from 0.1 m to 0.2 rids.
20 Therefore, a Doppler frequency fir can be obtained by the followingformulas as is already known.
(Numerical formula 1) fit = {(2 X vr)/(C/ ú 2/2)} X f 25 In the numerical formula 1, vr is a velocity of water (or a mixture of water and soil), C a transmission velocity of an electromagnetic wave in a
1, vacuum, 2 a relative dielectric constant in the ground, and f a frequency of a transmitted signal.
Here, supposing a water velocity vr = 0.1 m/s, letting a velocity of an electromagnetic wave C = 3 X 108 m/s, 2 = 81, f = 400 MHz when a s dielectric constant of the atmosphere is supposed to be 1 which equals to that of a vacuum, a Doppler frequency fd is obtained as follows: (Numerical formula 2) fit = {(2 X 0.1)/(3 X 108/81/2)} X 400 X 106 = 0.2 X 9 X 400 X 106/3 X 108
10 =2.4 Hz Here, when a water velocity is supposed to be 0.2 m/s, fd = 4. 8 Hz.
FIG. 8 shows a value of a Doppler frequency relative to an operating frequency obtained according to the numerical formula 1 described above. In FIG. 8 a horizontal axis shows an operating frequency with its unit being 15 MHz, and a vertical axis shows a Doppler frequency with its unit being Hz.
A sign in the chart is a value when a water velocity is supposed to be 0. 1 rn/s, when a water velocity is supposed to be 0.2 rn/s, X when a water velocity is supposed to be 0.4 m/s, O when a water velocity is supposed to be 0.5 m/s. Note that a relative dielectric constant in the ground saturated with 20 water is supposed to be 81.
From FIG. 8, a Doppler frequency calculated when an operating frequency is 400 MHz is 12 Hz even when a velocity of water leaking from a water pipe is O.S m/s. Therefore, taking FIG. 7 into consideration, a band frequency of the bandpass filter 84 may be set to be *tom about 0.5 Hz to 50 2s Hz. It is also apparent that when an operating frequency is supposed to be 600 MHz, a band frequency of the bandpass filter 84 may be set to be
approximately from 0.5 Hz to 100 Hz.
Industrial Availability As described above, an antenna according to the present invention is a s so-called half-wave antenna with the dimensions of a length and a width of a planar dipole antenna element made to be one half a wavelength A of an electromagnetic wave radiated in the ground, and as it has a frame box formed to be a cavity resonance type, it can obtain a big resonance characteristic and increase a gain for a frequency corresponding to a specific 10 wavelength A. Therefore, the antenna according to the present invention can radiate a strong electromagnetic wave of a specific frequency when used as a transmitting antenna, and can receive a reflected wave with less noise when used as a receiving antenna. Thus, the antenna of the present invention can easily perform the detection of a Doppler frequency and improve the 15 accuracy of detecting water leakage from a water pipe laid underground.
Furthermore, the present invention has a dielectric resonator, which is composed of, for example, ceramics, disposed to a transmission path connected to an antenna element, thereby can increase a Q value which shows the sharpness of resonance. Therefore, the antenna according to the 20 present invention can improve a resonance characteristic in a desired frequency to allow a transmitted signal to be narrow-band and can reduce the influence of a coming noise as well as improving a gain of transmitting and . recelvlng. The water leakage detector according to the present invention also has 2s a bandpass filter provided to an output side of an demodulator, and it passes therethrough a component in a demodulation signal outputted from the
demodulator corresponding to a Doppler frequency caused by Doppler effect due to a flow in a water leakage, so that the detection of a Doppler frequency can be performed easily and without mistake. In addition, as the water leakage detector of the present invention does not require a phase of a s reference signal given to the demodulator to be adjusted by a phase shifter as is conventionally required, it does not need a voltage comparator and a phase shifter, thereby simplifying its circuit. Thus, as the water leakage detector of the present invention does not require the phase of the reference signal to be adjusted, it can immediately perform the operation of detecting water leakage 10 even when the installation condition of the antenna is changed and a transmission frequency drifts due to temperature change, so that it becomes maintenance-free to improve operatability drastically. Furthermore, as the water leakage detector according to the present invention can increase an amplitude factor at the final stage of amplifying a signal which passes 5 through the bandpass filter, it can increase an SIN ratio.
Incidentally, the water leakage detector can reduce a noise by setting a band frequency of the bandpass filter to be 0.5 Hz or more and 1 kHz or less at which a direct-current component is removed.
An embodiment of the present invention provides: an antenna for a water leakage detector for detecting the existence and non existence of water leakage from a pipe laid underground by radiating an electromagnetic wave in the ground, receiving a reflected wave thereof, and detecting a Doppler frequency, comprising: -.
a planar dipole antenna element with its width and length made to be one half a wavelength of said electromagnetic wave radiated in the ground; and a frame box covering one side face of said antenna element to form a resonant cavity.
A dielectric resonator may be is provided to a transmission path connected to said planar dipole antenna element.
Claims (3)
1. A water leakage detector, having a transmitting antenna for radiating in the ground a transmitted signal composed of an electromagnetic wave and a receiving antenna for receiving a reflective wave of said transmitted signal radiated from said transmitting antenna, for detecting the existence or non-
existence of water leakage from an underground buried pipe based on said reflective wave received by said receiving antenna, said water leakage detector comprlsmg: a demodulator, inputting from a reference signal generator a reference signal of the same frequency as that of said transmitted signal radiated from said transmitting antenna while inputting a received signal from said receiving antenna, for outputting a demodulation signal from these signals, according to a phase shift relative to said transmitted signal; and a bandpass filter, inputting said demodulation signal outputted from said demodulator, for passing therethrough a component in said demodulation signal corresponding to a Doppler frequency caused by a flow in a water leakage part.
2. The water leakage detector according to claim 1, wherein a pass band of said bandpass filter is from O.5Hz to 1 kHz.
3. A water leakage detector substantially as herein described.
Priority Applications (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB0329045A GB2393872B (en) | 1999-12-03 | 1999-12-03 | Water leakage detector |
| GB0419228A GB2406294B (en) | 1999-12-03 | 2004-08-31 | Natural gas liquids |
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB0329045A GB2393872B (en) | 1999-12-03 | 1999-12-03 | Water leakage detector |
| GB0116258A GB2362529B (en) | 1999-12-03 | 1999-12-03 | Water leakage detector and antenna thereof |
Publications (3)
| Publication Number | Publication Date |
|---|---|
| GB0329045D0 GB0329045D0 (en) | 2004-01-14 |
| GB2393872A true GB2393872A (en) | 2004-04-07 |
| GB2393872B GB2393872B (en) | 2004-05-26 |
Family
ID=31971109
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB0329045A Expired - Fee Related GB2393872B (en) | 1999-12-03 | 1999-12-03 | Water leakage detector |
Country Status (1)
| Country | Link |
|---|---|
| GB (1) | GB2393872B (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2011046480A1 (en) * | 2009-10-15 | 2011-04-21 | Totalförsvarets Forskningsinstitut FOI | Device and method for detection of water flow in ground |
| US9594161B2 (en) | 2011-03-11 | 2017-03-14 | Totalforsvarets Forskningsinstitut | Method and device for searching through collapsed ground |
Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH11352001A (en) * | 1998-06-04 | 1999-12-24 | Mitsui Eng & Shipbuild Co Ltd | Water leakage detector |
-
1999
- 1999-12-03 GB GB0329045A patent/GB2393872B/en not_active Expired - Fee Related
Patent Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH11352001A (en) * | 1998-06-04 | 1999-12-24 | Mitsui Eng & Shipbuild Co Ltd | Water leakage detector |
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2011046480A1 (en) * | 2009-10-15 | 2011-04-21 | Totalförsvarets Forskningsinstitut FOI | Device and method for detection of water flow in ground |
| US9057792B2 (en) | 2009-10-15 | 2015-06-16 | Totalforsvarets Forskningsinstitut | Device and method for detection of water flow in ground |
| EP2488845A4 (en) * | 2009-10-15 | 2016-10-19 | Totalförsvarets Forskningsinstitut FOI | Device and method for detection of water flow in ground |
| US9594161B2 (en) | 2011-03-11 | 2017-03-14 | Totalforsvarets Forskningsinstitut | Method and device for searching through collapsed ground |
Also Published As
| Publication number | Publication date |
|---|---|
| GB0329045D0 (en) | 2004-01-14 |
| GB2393872B (en) | 2004-05-26 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PCNP | Patent ceased through non-payment of renewal fee |
Effective date: 20051203 |