Fluid detector
The fluid detector addresses the complexity and cost issues of existing methods by using an electromagnetic waveguide with a substrate that changes dielectric constant upon fluid impregnation, enabling efficient and inexpensive leak detection in challenging environments.
Patent Information
- Application Number
- FR2022010119
- Authority / Receiving Office
- FR · FR
- Patent Type
- Patents
- Current Assignee / Owner
- Priority Date
- 2021-11-18
- Filing Date
- 2022-10-04
- Publication Date
- 2024-12-13
- Estimated Expiration
- 2042-10-04
AI Technical Summary
Existing leak detection methods for fluids are complex, costly, and not suitable for permanent monitoring, inducing high investment and time costs.
A fluid detector using an electromagnetic waveguide with a substrate that changes dielectric constant upon fluid impregnation, comprising conductive strips and measurement means to detect phase shifts, allowing for simple and inexpensive fluid presence detection.
Enables cost-effective and straightforward detection of fluid leaks by measuring dielectric constant variations, suitable for environments with extreme conditions, including nuclear power plants and factories.
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Abstract
Description
Title of the invention: Fluid detector Technical field of the invention
[0001] The present invention relates generally to the detection of fluids, and in particular to the detection of leaks of such fluids. Technical background
[0002] Leak detection or leak testing is one of the disciplines that is part of the control techniques implemented in a large number of industries or applications. Multiple products use leak detection, measurement and location techniques either because the fluid that we are trying to confine inside or outside an enclosure is expensive, available in limited quantity, dangerous, toxic, harmful to the environment, capable of causing damage around the leak point, or has the aim of transforming an atmosphere for the preservation of contents or the reduction of a risk. There are non-destructive methods, for example by tracer gas, and there are also invasive methods, for example by pressure attenuation or by flow measurement.
[0003] The leakage flow or leak rate is expressed in different units depending on the intended application. In refrigeration, we generally speak in grams per year to designate the loss of refrigerant liquid in one year (for example: the limit leak rate on a car air conditioner is 5 g / year). In other applications, we use the millibar liter per second or mb.l / s or even in atmosphere cubic centimeter per second or atm.cm3 / s. The unit used in the metric system is the pascal cubic meter per second or Pa.m3 / s.
[0004] All these techniques aim to detect the presence of a fluid in a given environment which could, in an example application, reveal the existence of a leak.
[0005] There are methods based on tracer gases. However, these methods are complex to implement and are not suitable for permanent monitoring of a given environment.
[0006] There are also methods based on measuring the variation of pressure over time or measuring flow rate or even detecting acoustic waves specific to the leak of the fluid being sought.
[0007] All these methods induce additional efforts which cause high costs and a relatively large investment in time. Summary of the invention
[0008] Based on these problems, the present invention therefore has the task of developing a new, inexpensive and easy-to-implement fluid detector.
[0009] As regards fluid detectors, the task on which the invention is based is solved by a novel fluid detector as described below.
[0010] According to one of its embodiments, the invention relates to a fluid detector comprising an electromagnetic waveguide comprising a substrate, said substrate comprising a material whose dielectric constant has at least a first value representative of the absence of the fluid in the material and a second value representative of the presence of the fluid in the material, the detector comprising means for measuring a parameter representative of the value of the dielectric constant of the material
[0011] According to one embodiment of the present invention, the substrate is a substrate of the type capable of being impregnated with the fluid.
[0012] According to one embodiment of the present invention, the substrate is a fabric comprising threads made of dielectric material.
[0013] According to an embodiment of the present invention, the electromagnetic waveguide is a microstrip line comprising a first electrically conductive strip secured to a first face of the substrate and a second electrically conductive strip secured to a second face of the substrate. The upper strip may be on the surface or inside the volume.
[0014] According to one embodiment of the present invention, the first and second conductive strips are sewn onto the fabric. According to one embodiment of the invention, the first and second conductive strips are affixed to the fabric by another adhesion method.
[0015] According to one embodiment of the present invention, at least one of the first and second conductive bands is a radiofrequency band.
[0016] According to one embodiment of the present invention, at least one of the first and second conductive strips comprises a fabric comprising threads made of electrically conductive material.
[0017] According to one embodiment of the present invention, at least one of the first and second conductive strips is an impedance-matched track. According to one embodiment of the present invention, at least one of the first and second conductive strips is a track that has an impedance of about 50 ohms.
[0018] According to an embodiment of the present invention, the fluid detector is a detector of the presence of a gas or a liquid in a nuclear power plant or in a factory. According to an embodiment of the present invention, the fluid detector is a water leak detector and more particularly a water leak detector for a nuclear power plant or in a factory.
[0019] According to one embodiment of the present invention, the fluid detector also includes a synchronized two-channel synthesizer, a wave mixer, and a multimeter. According to one embodiment of the present invention, the fluid detector also includes a comparator. According to one embodiment of the present invention, the fluid detector also includes a synchronized two-channel synthesizer, a comparator, and a multimeter.
[0020] The invention further relates to a method for manufacturing a fluid detector, in particular a fluid detector of the type according to the invention indicated above. Brief description of the figures
[0021] Other characteristics and advantages of the invention will appear during the reading of the detailed description which follows for the understanding of which reference will be made to the appended drawings in which:
[0022] [Fig.l] shows schematically and in an isometric view, an exemplary embodiment of a fluid detector 1 according to the invention;
[0023] [Fig.2] schematically shows an example of a test device for the detector of [Fig.l];
[0024] [Fig.3] shows schematically an example of a substrate in the form of a fabric for the detector of [Fig.l];
[0025] [Fig.4] shows schematically an example of a substrate in the form of a fabric for the detector of [Fig.l];
[0026] [Fig.5] illustrates the effect of humidifying or drying the detector according to the invention of [Fig.l] on an oscilloscope. Detailed description of the invention
[0027] Various aspects of various embodiments of fluid detectors according to the invention are described in more detail below, with reference to the accompanying drawings.
[0028] In devices for transmitting electromagnetic waves, the basic principle is to allow the propagation of a wave with the best possible integrity and the least possible power loss by using, for example, guided propagation modes. Among these waveguide devices, there are single-conductor guides such as rectangular guides and circular guides and two-conductor guides such as coaxial cords and microstrip lines.
[0029] These guides have in common the guided propagation of the wave by means of a substrate or a propagation medium having a dielectric constant or permittivity which is complex, that is to say that it has a real part and an imaginary part.
[0030] The imaginary part corresponds to an attenuation and the real part corresponds to the change in speed of the wave when it crosses the dielectric medium. We speak also tangent delta to characterize the absorption which amounts to the same thing.
[0031] Conventionally, a microstrip line comprises a propagation track made of an electrically conductive material, a substrate and a ground plane which is also electrically conductive.
[0032] The relative dimensions and distances of the line components make it possible to optimize the device as a function of the frequency with impedance matching. The tracks can be on the surface or in the substrate.
[0033] In such a device and in the classic case, a dielectric material is used for the substrate in the range of "epoxy" or low-loss materials depending on the desired frequency or frequency band.
[0034] It should be noted that the propagation speed of the wave is directly linked to the value of the real part of the dielectric constant. When the electromagnetic wave travels a certain distance in the line, it will travel a certain electrical length associated with a propagation time.
[0035] This propagation time, often measured in nanoseconds, can be measured by analyzing an echo propagating in the line and analyzing its travel time. Between the start and the end of the line, the wave therefore takes a time expressed in nanoseconds. This more expensive method can obviously be used using conventional hyperfrequency measurement techniques.
[0036] When this wave is a sinusoidal wave in particular, the time and distance traveled correspond to a phase difference between the start and the end of the line.
[0037] The devices for measuring the phase at the output of such a line can take into account a reference phase, for example measured on a reference line whose permittivity is constant over time. The distance traveled in the line to be measured and the reference line are identical.
[0038] For example, an electromagnetic signal may be divided into a first signal (hereinafter the reference signal) and a second signal (hereinafter the signal to be measured) before they are introduced into lines. The reference signal then passes over a first line (hereinafter the reference line) whose dielectric constant remains constant over time and the second signal passes over a second line (hereinafter the line to be measured) whose dielectric constant varies over time. For example, the two lines have the same length. After passing through the first and second lines, the phase shift between the first signal and the second signal reflects any change in the dielectric permittivity on the second line.
[0039] The phase shift measurement can be carried out in several ways. It can be carried out with a component comparing the phase of the two signals and which generates an electrical voltage at the output. It can also be carried out using a passive mixer circuit which compares the same frequency on the RF (radio frequency) and OL channels. (local oscillator) and generates a voltage depending on the phase difference and the frequency (and resulting from the electronic mixing from the 2 compared channels).
[0040] Since the dielectric constant remains constant on the second line (the first being constant or known and serving as a reference), the distance traveled and the phase resulting from the comparison are also constant. Thus, the measured voltage also remains constant.
[0041] On the other hand, if the dielectric constant changes on the second line, then the output voltage of the device will change accordingly.
[0042] Such a voltage measurement which can be digitized and possibly calibrated makes it possible to follow the phase variation reflecting the variation of permittivity in the second line.
[0043] A fluid detector according to a first embodiment of the invention is presented in relation to [Fig. 1].
[0044] Advantageously, the detector 1 comprises an electromagnetic waveguide 2 comprising a substrate 3.
[0045] Preferably, the detector comprises means for measuring a parameter representative of the value of the dielectric constant of the material. For example, these measuring means are those described above.
[0046] For example, the electromagnetic waveguide 2 is a microstrip line comprising a first electrically conductive strip 4 secured to a first face of the substrate 3 and a second electrically conductive strip 5 secured to a second face of the substrate 3. Of course, in accordance with the invention, the waveguide 2 may be any other electromagnetic waveguide with one conductor such as a rectangular waveguide or a circular waveguide or any other electromagnetic waveguide with two conductors such as the coaxial waveguide, coplanar waveguides, parallel plates, etc.
[0047] Advantageously, the substrate 3 comprises a material whose dielectric constant has at least a first value representative of the absence of the fluid in the material and a second value representative of the presence of the fluid in the material.
[0048] For example, the substrate comprises a dielectric material. For example, the substrate 3 is a substrate of the type that can be impregnated with the fluid. Advantageously, the substrate 3 is a fabric comprising threads made of dielectric material. For example, these threads are made of cotton, plastic (for example PVC), a synthetic material (for example polyimide, resin, polymer, elastomer or composite or any other synthetic material), epoxy, ceramic, glass (for example glass fibers), ceramic, mica or any other material or even any combination of two or more of the aforementioned materials. For example, the fabric can be a High Temperature Fabric marketed by the industry as standard or according to specific specifications.
[0049] Advantageously, the first and second conductive strips are sewn onto the fabric, for example with conductive sewing threads.
[0050] It may be advantageous to apply such a detector according to the invention to detect the presence of a fluid (gas or liquid) in an environment, for example to detect a leak of a liquid, for example a water leak (or a leak of any other liquid) in an environment for example in a nuclear power plant (or any other environment). Of course, any other application of the detector according to the invention is possible. For example, the detector may be a detector of the presence of a gas or a liquid in a nuclear power plant.
[0051] In particular, the detector can be used as a movement and / or presence sensor, or detector of the mechanical modification of a structure and / or of the physicochemical modification of a structure since the variation of the electromagnetic parameters can be detected at the level of the variation analysis device.
[0052] In a particular case, we can use a substrate which can be impregnated with the fluid to be detected, the impregnation of the substrate modifying its dielectric constant.
[0053] Thus, taking into account the laws of propagation described above, the water impregnation of the fabric of the substrate 3 of the microstrip line of the detector 1 modifies the propagation speed of Fonde and thus the value of the phase shift and the propagation time of the wave.
[0054] For example, the measuring means of the detector 1 comprise one or more of the following devices: a frequency synthesizer or any other generation mode, a directional divider or coupler, a track under test, a reference track, a combiner or coupler, a mixer or a phase comparator, and a digitizing or voltage measuring device.
[0055] Thus, in accordance with the invention, the variation of the phase after propagation in the waveguide can be measured. It is also possible to measure the propagation speed or a directly related quantity, and therefore to deduce the variation in permittivity due to the water impregnation of the fabric and therefore to deduce the presence of water in the fabric and therefore in the environment of the detector 1. This makes it possible, for example, to detect a water leak.
[0056] This detector 1 can also be associated with embedded software detecting and alerting on the variation in measured voltage, this detector being able to be simply connected to a monitoring or alarm system.
[0057] For example, at least one of the first and second conductive bands is a radio frequency band.
[0058] For example, the first conductive strip (or track) and the second strip conductive (or mass plane) are radiofrequency (or RF) strips. For example, they are sewn to the fabric of the substrate 3. Of course, the strips can be secured to the substrate by any other means. For example, at least one of the first and second conductive strips is a 50 ohm track (for example, copper). For example, the first strip 4 is a 50 ohm track. For example, this first strip 4 comprises a conductive textile. It can be solid or perforated depending on the wavelength to be propagated in the guide. The width w of the first strip 4 influences the impedance matching.
[0059] For example, at least one of the first and second conductive strips comprises a fabric comprising wires of electrically conductive material, for example copper or steel wires.
[0060] For example, the second conductive strip 5 (ground plane) comprises a conductive textile (fabric comprising wires made of electrically conductive material). Of course, any other conductive material may be suitable for producing the second strip 5. The width of the second strip 5 is W in [Fig.l].
[0061] In certain cases if the waveguide 2 is placed on a metal support the ground plane (or second strip 4) may not be necessary.
[0062] The dimensions of the first and second bands as well as of the substrate are preferably chosen as a function of the wavelength used for the wave to be propagated in the detector. Preferably, W is significantly greater than w.
[0063] The frequencies used are, for example, between 500 MHz and 1.5 GHz.
[0064] For example, the detector 1 comprises in particular: a waveguide 2 based on high-temperature textile (for example more than 600°C), a synchronized two-way synthesizer, a wave mixer, coaxial cords to the reference line and to the waveguide 2 and a multimeter for measuring the voltage. For example, the microwave frequency used is 1.5 GHz and the power is of the order of 1 mW.
[0065] Figures 2 to 4 illustrate the detector 1 according to one embodiment of the invention.
[0066] [Fig.2] illustrates an example of a test device for the detector 1. For example, such a test device includes an oscilloscope 21 and a multimeter 22.
[0067] [Fig. 3] illustrates an example of a substrate 3 capable of being impregnated with the fluid in the form of a fabric 31 comprising wires made of dielectric material for the detector 1.
[0068] [Fig.4] also illustrates an example of a substrate 3 capable of being impregnated with the fluid. in the form of a fabric 31 comprising wires made of dielectric material for the detector 1. In [Fig.4], the detector is placed in situation.
[0069] [Fig. 5] illustrates the effect of humidification or drying of the detector 1 on an oscilloscope 50. The screen of the oscilloscope makes it possible to detect variations in the measured voltage. Curve 51 is an event capture by piezo-sensor electrical diagram showing the effect of water droplets being projected onto the detector.
[0070] Thus, due to the existence of synthetic fabrics with extreme performance, thanks to the invention, it is possible to produce such detectors adapted to extreme environments or conditions, for example environments with very high or very low temperatures or pressure, environments comprising strong radiation emitters, very polluted environments, etc. Standard detectors are not adapted to these environments / conditions.
[0071] In the case of textile materials it is possible to produce a detector as described above using:
[0072] - A conductive thread sewn in order to make the track and the ground plane, the track and the ground that can be either soldered or sewn to a coaxial type connector for example;
[0073] - A substrate made of textile material capable of being impregnated with the fluid and having a ca dielectric characteristic.
[0074] Another advantage of such a detector or sensor is that the active part of the phase measurement can be moved away from the area or environment with extreme conditions.
[0075] The invention relates in particular also to a method for manufacturing and / or mounting a corresponding fluid detector. List of reference signs
[0076] 1 fluid detector
[0077] 2 electromagnetic waveguide
[0078] 3 substrate
[0079] 31 fabric
[0080] 4 first electrically conductive strip
[0081] 5 second electrically conductive strip
[0082] 21 oscilloscope
[0083] 22 multimeter
[0084] 50 oscilloscope
[0085] 51 yellow curve
Claims
Claims
1. Fluid detector (1) characterized in that it comprises an electromagnetic waveguide (2) comprising a substrate (3), said substrate comprising a material whose dielectric constant has at least a first value representative of the absence of the fluid in the material and a second value representative of the presence of the fluid in the material, and in that it comprises means for measuring a parameter representative of the value of the dielectric constant of the material, and in that the electromagnetic waveguide (2) is a microstrip line comprising a first electrically conductive strip (4) secured to a first face of the substrate and a second electrically conductive strip (5) secured to a second face of the substrate.
2. Fluid detector (1) according to claim 1, characterized in that the substrate (3) is a substrate of the type capable of being impregnated with the fluid.
3. Fluid detector (1) according to any one of claims 1 and 2, characterized in that the substrate (3) is a fabric comprising wires made of dielectric material.
4. Fluid detector (1) according to claim 3, characterized in that the first and second conductive strips are sewn onto the fabric.
5. Fluid detector (1) according to any one of claims 1 to 4, characterized in that at least one of the first and second conductive strips is a radiofrequency strip.
6. Fluid detector (1) according to any one of claims 3 to 5, characterized in that at least one of the first and second conductive strips comprises a fabric comprising threads of electrically conductive material.
7. A fluid detector (1) according to any one of claims 1 to 6, characterized in that at least one of the first and second conductive strips is a track which has an impedance of approximately 50 ohms.
8. Fluid detector (1) according to any one of the preceding claims, characterized in that it is a detector of the presence of a gas or a liquid in a nuclear power plant or in a factory.
9. Fluid detector (1) according to any one of the preceding claims, characterized in that it also comprises a synchronized two-channel synthesizer, a wave mixer, and a multimeter.