WO2015165554A1

WO2015165554A1 - Electromagnetic opening for a multi-phase flow meter based on rf energy

Info

Publication number: WO2015165554A1
Application number: PCT/EP2014/073785
Authority: WO
Inventors: Maksim Berezin; Ram ELBOIM; Eli Dichterman; Ben ZICKEL
Original assignee: Goji Limited
Priority date: 2014-05-02
Filing date: 2014-11-05
Publication date: 2015-11-05

Abstract

Described is an apparatus for determining a value of a property of a flowing material that flows through the apparatus. In some embodiments, the apparatus includes an RF cavity, a detector, and an electromagnetically obstructing member. The RF cavity extends between a first end and a second end and is configured to allow the flowing material to flow through the RF cavity from the first end to the second end. The detector is configured to detect electrical responses of the RF cavity to incoming RF signals of various frequencies, and generate signals indicative of the detected electrical responses; and the electromagnetically obstructing member is positioned at (at least) one of the first end and the second end of the RF cavity without obstructing flow of material through the at least one of the first end and second end of the RF cavity.

Description

ELECTROMAGNETIC OPENING FOR A MULTI-PHASE FLOW METER

BASED ON RF ENERGY

BACKGROUND OF THE INVENTION

[001] The present application is in the field of investigating materials by the use of microwave. More particularly but not exclusively, some embodiments are in the field of investigating phase composition of crude oil or other multi-phase materials.

[002] Proposals to investigate multi-phase materials using microwave have been made at least since the 1970s, but to the best of the knowledge of the inventors, such proposals never matured into a commercially available product. Accordingly, the inventors believe that the field may benefit from a new approach.

SUMMARY OF THE INVENTION

[003] An aspect of some embodiments of the invention includes an apparatus for determining a value of a property of a flowing material, which may be a multi-phase material, that flows through the apparatus. The apparatus may include: an RF opaque member (e.g., an RF cavity), a detector, and an electromagnetically obstructing member. The RF cavity may extend between a first end and a second end and is configured to allow the flowing material to flow through the RF cavity from the first end to the second end. The detector may be configured to detect electrical responses of the RF cavity to incoming RF signals of various frequencies, and generate signals indicative of the detected electrical responses; and the electromagnetically obstructing member is positioned at at least one of the first end and the second end of the RF cavity without obstructing flow of the material through said at least one of the first end and second end of the RF cavity.

[004] In some embodiments, the electromagnetically obstructing member comprises an RF transparent member sized and positioned to form an electromagnetic opening between the RF cavity and a pipe feeding the RF cavity with the flowing material.

[005] Alternatively or additionally, the electromagnetically obstructing member may comprise an RF absorbing member comprising a hollow conduit having RF absorbing wall.

[006] In some embodiments, changing the boundary conditions along a pipe feeding the RF cavity with the flowing material does not change readings of the detector by more than a predetermined degree. [007] In some embodiments, the RF cavity has at the first end an opening with an opening-dimension defining an opening cutoff frequency, and wherein said various frequencies include at least one frequency above the opening cutoff frequency.

[008] In some embodiments, the various frequencies may span a frequency range, the highest frequency thereof is at least 3 times higher than the lowest frequency thereof. In some embodiments, at least a quarter of said frequency range is above the opening cutoff frequency.

[009] In some embodiments, the apparatus may include a sensor. The sensor may include the RF cavity, the detector, and an RF transparent conduit located within the RF cavity. The RF transparent conduit may be configured to direct the flowing material through the RF cavity. In some embodiments, the RF transparent conduit has substantially the same dielectric constant as the flowing material.

[0010] In some embodiments, an inner dimension of the RF cavity is larger than the opening dimension.

[0011]

[0012] 11. An apparatus according to any one of claims 1 to 10, wherein the RF transparent conduit and the electromagnetically obstructing member are configured so that material flowing through the RF cavity continues flowing without obstruction through the RF transparent member or vice versa.

[0013] In some embodiments, the apparatus may include two electromagnetically obstructing members, one at each end of the RF cavity.

[0014] In some embodiments, the RF cavity and the electromagnetically obstructing members are so configured, that material flowing through one electromagnetically obstructing member continues flowing without obstruction through the RF cavity, and from the RF cavity through the other electromagnetically obstructing member.

[0015] In some embodiments, the sensor comprises a feed for feeding the RF cavity with RF radiation, and the feed comprises a radiating element ending outside the RF cavity.

[0016] In some embodiments, the apparatus comprises a source of RF radiation configured to supply RF radiation at the various frequencies to the RF cavity through the feed. The apparatus may further include a processor configured to determine the value of the property based on the signals generated by the detector. [0017] Thus, according to some embodiments of the invention, there may be provided an apparatus for determining a value of a property of a material flowing inside a pipe, wherein the apparatus includes:

[0018] a radio frequency (RF) resonator extending between a first end and a second end, each end having an opening to allow the material to go in and out the RF resonator, wherein said opening defines an opening cutoff frequency;

[0019] at least one feed configured to feed the resonator with RF radiation;

[0020] at least one source configured to supply to the feed RF energy at a frequency range, wherein at least 1/4 of the frequency range is above the opening cutoff frequency;

[0021] a detector, configured to detect parameters indicative of electrical response of the RF resonator to radio frequency (RF) radiation fed to the RF resonator through the at least one feed;

[0022] a processor, configured to determine the value of the property based on the parameters detected by the detector; and

[0023] an electromagnetically obstructing member, between the resonator and the pipe, electromagnetically isolating the resonator from the pipe without obstructing material flow from the pipe through the resonator.

[0024] In some embodiments, the electromagnetically obstructing member may comprise an RF transparent member sized to form an open electromagnetic boundary. Alternatively or additionally, the electromagnetically obstructing member may comprise an RF absorbing member sized to form an electromagnetic obstruction at least at those of the various frequencies that are higher than the opening cutoff frequency.

[0025] In some embodiments, during operation of the apparatus, the electric field at some surface between the resonator and the RF obstructing member is larger by at least factor 100 than between the RF obstructing member and the pipe.

[0026] There may also be provided by an aspect of some embodiments of the invention a method of determining a value of a property of a material that flows in a pipe. The method may include replacing a portion of the pipe by an apparatus as described above; and operating the apparatus to determine the property.

[0027] In some embodiments, the sensor may include a plurality of feeds, each configured to deliver RF radiation to the RF opaque member to excite multiple modes in the RF opaque member. One or more of the feeds may be inclined in respect of the RF opaque member. In some embodiments, each of the feeds includes a radiating element exterior to the RF opaque member and a waveguide configured to guide electromagnetic waves from the radiating element to the RF opaque member. The sensor may further include a detector that detects parameters indicative of an electrical response of the RF opaque member to RF radiation (e.g., in the form of RF signals) delivered to the RF opaque member at a plurality of frequencies, and a processor, that determines the value of the property of the flowing material (e.g., the flow rate of the multi-phase material) based upon the parameters detected by the detector.

[0028] The apparatus may include a pressure sensor configured to measure differential pressure of the multi-phase material and a temperature sensor configured to measure a temperature of the multi-phase material.

[0029]

[0030] In some embodiments, a feed may include a radiating element having an end, and a waveguide for guiding waves from the end of the radiating element to the RF opaque member. In some such embodiments, the end of the radiating element may be distanced from the RF opaque member by half a wavelength or more. The wavelength may be the wavelength in the waveguide of the lowest frequency of the microwave radiation exciting the modes in the RF opaque member.

[0031] In some embodiments, the material under investigation may be familiar in the sense that the material has a dielectric constant within a given range. In some such embodiments, the conduit (within which the material may flow in operation) may be made of a dielectric material having a dielectric constant within the said given range. For example, the conduit may be made of a material having a dielectric constant within a lower half of the said given range.

[0032] In some embodiments, the waveguide may have a cutoff frequency that is lower than or equal to the inner cutoff frequency of the RF opaque member.

[0033] In some embodiments, a diameter of the waveguide is half or less a diameter of the RF opaque member.

[0034] In some embodiments, the processor may be configured to determine the value of the property of the material under investigation by applying a kernel method to measurement results associating frequencies (or other excitation setups) with values of parameters indicative of the electrical response of the RF opaque member to the excitation.

[0035] In some embodiments, the parameters indicative of electrical response of the RF opaque member to the excitation of the modes in the RF opaque member include a ratio of power measured to get back from the RF opaque member at a given feed to power measured to go towards the RF opaque member at the given feed. For example, the parameters indicative of electrical response of the RF opaque member to the excitation of the modes in the RF opaque member include a scattering parameter Sn.

[0036] In some embodiments, the values of parameters indicative of the electrical response of the RF opaque member to the excitation may include values measured by the detector.

[0037] In some embodiments, the processor may be configured to combine parameters measured by the detector to obtain combined parameters. The processor may be further configured to determine the property based on the combined parameters. In some embodiments, each combined parameter is associated with one of the feeds. Examples of parameters that may be used by the processor for determining the value of the property of the object may include s parameters, Γ parameter, and dissipation ratios.

[0038] According to some embodiments of the invention, there is provided a method of determining a value of a property of a material that flows in a conduit inside an RF opaque. The method may include:

exciting multiple modes in the RF opaque member through a number of feeds;

detecting parameters indicative of electrical response of the RF opaque member to the excitation of the modes in the RF opaque member; and determining the value of the property based on the detected parameters.

[0039] In some embodiments, the method may include:

irradiating microwave radiation into the RF opaque member at a plurality of excitation setups, each defining a set of controllable parameters that affect a field pattern excited in the RF opaque member;

detecting parameters indicative of electrical response of the RF opaque member to the irradiated microwaves; and

determining the value of the property based on the detected parameters. [0040] In some embodiments, at least one of the feeds comprises a radiating element outside the RF opaque member and a waveguide configured to guide waves from the radiating element to the RF opaque member.

[0041] In some embodiments, the excitation of the multiple modes in the RF opaque member may include excitation of a number of modes that is larger than the number of feeds.

[0042] In some embodiments, the determination of the value of the property may include application of kernel methods. These methods may be applied to parameters measured by the detectors. In some embodiments, the kernel methods may be applied to combined parameters. The combined parameters may be combinations of the measured parameters. In some embodiments, these combinations may be linear. In some embodiments, these combinations may be non-linear.

[0043] Accordingly, in some embodiments, determining the value of the property comprises combining parameters measured by the detector to obtain combined parameters, and determine the property based on the combined parameters.

[0044] In some embodiments, the method may include operating an apparatus, which by itself is according to some embodiments of the present invention.

[0045] In some embodiments, exciting a number of modes is by applying to the RF opaque member RF radiation at a plurality of excitation setups. In some embodiments, each two of the excitation setups differ from one another in at least one of a frequency or a feed, through which RF radiation is fed to the RF opaque member to obtain the excitation.

[0046] In some embodiments, the flowing material is a multi-phase material, for example, crude oil or milk. In some such embodiments, the property may be a phase-composition of the material, or a volume fraction of one of the material's components, for example, the volume fraction of water in the material, the volume fraction of oil in the material, etc.

[0047] According to an aspect of the present disclosure, an apparatus is provided for determining a flow rate of a multi-phase material that flows in a conduit of an RF opaque member (e.g., a microwave cavity). The apparatus may include a multi-mode RF opaque member through which the conduit extends, a plurality of inclined parallel feeds, each of the feeds configured to deliver RF radiation to the RF opaque member to excite multiple modes in the RF opaque member, each of the feeds comprising a radiating element exterior to the RF opaque member and a waveguide configured to guide electromagnetic waves from the radiating element to the RF opaque member, a detector that detects parameters indicative of an electrical response of the RF opaque member to RF radiation delivered to the RF opaque member, and a processor, that determines the flow rate of the multi-phase material based upon the parameters detected by the detector.

[0048] The apparatus may also include an attenuator having an RF reflective attenuating conduit portion and a dielectric attenuating conduit portion. The apparatus may also include a plurality of attenuators, in which each of the plurality of attenuators has an RF reflective attenuating conduit portion and a dielectric attenuating conduit portion. In another aspect, an attenuator may have a metallic attenuating conduit portion and a dielectric attenuating conduit portion. Further, a plurality of attenuators may be provided in which each of the plurality of attenuators has a metallic attenuating conduit portion and a dielectric attenuating conduit portion.

[0049] Still further, the apparatus may include a pressure sensor configured to measure differential pressure of the multi-phase material and a temperature sensor configured to measure a temperature of the multi-phase material. Yet further, the apparatus may include an inlet to the RF opaque member and an outlet to the RF opaque member, in which at least one of the inlet and the outlet is at least partially covered by a net. In one aspect, the net contains a metallic material.

[0050] Further, different frequencies can be applied to each of the plurality of inclined feeds at the same time. Additionally, excitation can be applied to less than all of the plurality of inclined parallel feeds at a given time. In one aspect the multi-phase material includes a wet gas and/or crude oil.

[0051] According to another aspect of the present disclosure, a method is provided for determining a flow rate of a multi-phase material that flows in a conduit of an RF opaque member. The method includes exciting multiple modes in the RF opaque member through a plurality of inclined parallel feeds, in which each of the feeds includes a radiating element exterior to the RF opaque member and a waveguide configured to guide electromagnetic waves from the radiating element to the RF opaque member. The method also includes detecting parameters indicative of an electrical response of the RF opaque member to RF radiation (e.g., RF signals) delivered to the RF opaque member. Additionally, the method includes determining the flow rate of the multi-phase material based upon the parameters detected by the detector. The method may include detecting an object flowing in the multi-phase material. The method may also include measuring reflected signals from the multi-phase material to identify a substance foreign to the multiphase material. The method may also include analyzing the reflected signals to identify a substance foreign to the multi-phase material. Still further, the method may include detecting a flow rate of a gas flowing in the multi-phase material. Yet further, the method may include measuring a differential pressure of the multi-phase material and measuring a temperature of the multi-phase material.

[0052] Further, the method may include transmitting an alarm signal upon a detection of a foreign substance in the multi-phase material. In one aspect the multi-phase material includes a wet gas and/or crude oil. Further, the method may include applying different frequencies to each of the plurality of inclined parallel feeds at the same time. Still further, the method may include applying excitation to less than all of the plurality of inclined parallel feeds at a given time.

[0053] An aspect of some embodiments of the invention relates to a method of determining a value of a property of a flowing material that flows in a conduit inside an RF opaque member. The method may include:

exciting a plurality of excitation setups in the RF opaque member through a plurality of feeds;

detecting parameters indicative of electrical response of the RF opaque member to the excitation of the excitation setups in the RF opaque member; and determining the value of the property based on the detected parameters by application of a kernel method.

[0054] In some embodiments, each two of the plurality of excitation setups differ from one another in at least one of a frequency or a feed.

[0055] In some embodiments, the parameters indicative of electrical response of the microwave RF opaque member to the excitation of the excitation setups in the microwave RF opaque member include a scattering parameter Sn.

[0056] In some embodiments, material is crude oil.

[0057] In some embodiments, the property includes a volume fraction of water in the material, a volume fraction of oil in the material and/or a volume fraction of gas in the material. [0058] Unless otherwise defined, all technical and/or scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the invention pertains. Some methods and materials that can be used in the practice or testing of embodiments of the invention are described below. Yet, other or equivalent materials and methods can be used in the practice or testing of embodiments of the invention. In addition, the materials, methods, and examples are illustrative only and are not intended to be necessarily limiting.

[0059] Implementation of the method of embodiments of the invention can involve performing or completing selected tasks automatically. Moreover, according to actual instrumentation and equipment of embodiments of methods of the invention, several selected tasks could be implemented by hardware, by software or by firmware or by a combination thereof using an operating system.

[0060] For example, hardware for performing selected tasks according to embodiments of the invention could be implemented as a chip or a circuit. As software, selected tasks according to embodiments of the invention could be implemented as a plurality of software instructions being executed by a computer using any suitable operating system. In an exemplary embodiment of the invention, one or more tasks according to exemplary embodiments described herein are performed by a data processor, such as a computing platform for executing a plurality of instructions. In some embodiments, the data processor includes a volatile memory for storing instructions and/or data. In some embodiments, the data processor may include a non-volatile storage, for example, a magnetic hard-disk and/or removable media, for storing instructions and/or data. Optionally, a network connection is provided as well. A display and/or a user input device such as a keyboard or mouse are optionally provided as well.

BRIEF DESCRIPTION OF THE DRAWINGS

[0061] The subject matter regarded as the invention is particularly pointed out and distinctly claimed in the concluding portion of the specification. The invention, however, both as to organization and method of operation, together with objects, features, and advantages thereof, may best be understood by reference to the following detailed description when read with the accompanying drawings in which: [0062] Fig. 1A is a diagrammatic representation of an exemplary apparatus according to some embodiments of the invention;

[0063] Figs. IB and 1C are isometric views of two sensors with feeds according to some embodiments of the invention;

[0064] Fig. 2A is a diagrammatic illustration of an exemplary RF opaque member with isolated feeds according to some embodiments of the invention;

[0065] Figs. 2B-2D are diagrammatic illustrations of exemplary RF opaque members according to some embodiments of the invention;

[0066] Fig. 3 is a fiowchart of a method of determining a value of a property of a flowing material according to some embodiments of the invention;

[0067] Fig. 4 is a diagrammatic presentation of an exemplary apparatus with an electromagnetically obstructing member according to some embodiments of the invention;

[0068] Fig. 5A is a diagrammatic illustration of an exemplary apparatus with two electromagnetically obstructing members according to some embodiments of the invention;

[0069] Fig. 5B is a diagrammatic illustration of an exemplary apparatus with a metallic attenuating conduit portion according to some embodiments of the invention;

[0070] Fig. 6 is an exemplary architecture within which the multi-phase flow meter is used, according to some embodiments of the present disclosure; and

[0071] Fig. 7 shows an exemplary general computer system that includes a set of instructions for the multi-phase flow meter, according to an aspect of the present disclosure;

[0072] Fig. 8 is a fiowchart of an exemplary method of using the sensor of Fig. 1 A for estimating properties of unknown samples.

[0073] It will be appreciated that for simplicity and clarity of illustration, elements shown in the figures have not necessarily been drawn to scale. For example, the dimensions of some of the elements may be exaggerated relative to other elements for clarity. Further, where considered appropriate, reference numerals may be repeated among the figures to indicate corresponding or analogous elements.

DETAILED DESCRIPTION OF THE PRESENT INVENTION [0074] In the following detailed description, numerous specific details are set forth in order to provide a thorough understanding of the invention. However, it will be understood by those skilled in the art that the present invention may be practiced without these specific details. In other instances, well-known methods, procedures, and components have not been described in detail so as not to obscure the present invention.

[0075] The present disclosure is in the field of investigating materials by the use of microwave. More particularly but not exclusively, some embodiments are in the field of investigating phase composition of crude oil or other multi-phase materials.

[0076] An aspect of some embodiments of the invention includes an apparatus for determining a value of a property of a flowing material. For example, the property may be a volume fraction of water, and the value may be 5%. The flowing material may include a plurality of phases, for example, the material may be crude oil, comprising oil and water; milk, comprising water and fat, or any other multi-phase material. Preferably, at least one of the phases has dielectric properties (e.g., a dielectric constant) distinctive from the other phases.

[0077] The material may flow in a pipe, and the apparatus may include a tubular portion that replaces a portion of the pipe. For example, the tubular portion may include an RF resonator, inside which the flowing material flows. The resonator may be comprised in a sensor configured to sense the property of the flowing material when the material flows inside the sensor. This arrangement may allow measuring properties of the flowing material without interfering with the material's flow.

[0078] A dielectric constant of a material (or of a phase in a multi-phase material) is the ratio between a dielectric permittivity of the material and the permittivity of vacuum, and is generally expressed as a complex number. The dielectric constant is a dielectric property that relates to attenuation of EM waves passing through the material. The higher the imaginary part of the dielectric constant the stronger the attenuation of the EM waves over a path of similar length. A dielectric constant may also be indicative of the tendency of a material to disperse or reflect EM waves. The dielectric constant of a material is influenced by the temperature of the material. For example, for most dielectric materials the dielectric constant decreases with the rise in temperature. Furthermore, the dielectric constant depends on the frequency, since materials interact differently with EM waves of different frequencies. Therefore, for using the present methods and apparatuses, it is preferable if at least two phases or materials have distinct dielectric constant at the temperature and frequency under which measurements are taken.

[0079] The property to be estimated based on the investigation may be any property that affects the dielectric constant of the material, for example, volume fraction of any one of the phases, temperature of the material, chemical composition of the material (e.g., salts dissolved in one of the phases), presence of metal particles or other foreign bodies, etc. For example, in some embodiments it would be desirable to detect the presence and percentages of substances in petroleum products, including crude oil, as such substances can be harmful, cause pollution, and create inefficient burning. Accordingly, the materials to be investigated may include polyaromatic hydrocarbons (PAH), sulfur containing organic materials content, hydrogen sulfide content, nitrogen containing organic materials, tars, and other carbonaceous materials.

[0080] As used herein, a flowing material may be defined as a material having flowing capabilities. The material may be in a liquid state, a gas state, a liquid containing solid or other liquid particles (e.g., crude oil that include water), a gas suspending liquid droplets (e.g., an aerosol), or a gas suspending solid particles (e.g., fume). The material may also be single phase, e.g., single-phase and multi component (e.g., a solution).

[0081] Reference is made to Figs. 1A-1C that are diagrammatic representations of various exemplary sensors 100 according to some embodiments of the invention. Sensor 100 illustrated in Fig. 1A includes an RF opaque member 102 and a conduit 104, inside which a flowing material 105 may flow in operation. Sensor 100 may further include a detector 120 configured to detect electrical responses of the RF opaque member to incoming RF signals of various frequencies and generate signal indicative of the detected electrical response. Sensor 100 may include one or more feeds 106 for feeding the RF opaque member with the RF signals, an RF source 115 for generating the RF signals, and a processor 130, for determining the property of the material based on readings of the detector.

[0082] In some embodiments, RF opaque member 102 may include any material that is configured to block, absorb and/or reflect RF radiation (e.g., RF signals). The RF reflective and or absorptive material may be included in the inner walls of RF opaque member 102 or may coat the inner walls of RF opaque member 102, such that any RF signal that is applied to an inner space within the RF opaque member may be blocked by, absorbed by and/or reflected from member 102 inner walls. For example, RF opaque member may be made of a metallic material (e.g., iron or aluminum alloys), or may be made of a dielectric material (e.g., a glass or a polymer) and may be coated (on the inner walls) with RF reflecting, absorbing or blocking coating. RF opaque member 102 may have any hollow shape, for example, it may be cylindrical, prismatic, rectangular, etc. Examples of RF opaque members include an RF resonator, for example, an RF cavity, referred to herein as a cavity. An RF resonator may be any structure that preferentially absorbs some RF frequencies more than others, so that a curve of absorption vs. frequency (at the radio frequency range) has at least one local maximum. Similarly, a curve or a reflection coefficient of a resonator (e.g., the scattering parameter Sn) against frequency has at least one local minimum.

[0083] In some embodiments, RF opaque member 102 may have a hollow shape (e.g., shaped as a cylinder or a prism) that is open at both sides to allow material flow into and out of the RF opaque member. RF opaque members of cylindrical shape are illustrated in Figures 2B and 2C. In some embodiments, RF opaque member 102 may be or may be shaped as a resonance cavity having two flow openings (e.g., as illustrated in Fig. 2D). The flow openings may allow material to flow in and out of the RF opaque member. In such cases, RF radiation that is reflected from the walls of the RF opaque member or not absorbed by the walls of the RF opaque member (e.g., when the walls do not absorbed 100% of the RF radiation applied to the RF opaque member), may escape through the flow openings. RF radiation that escaped from the RF opaque member may interact with the surrounding of the sensor, and therefore, the boundary conditions at the flow opening may depend on the surroundings, for example, on the pipe portions adjacent to the sensor. In such embodiments, the surroundings may affect the readings of the sensor and reduce its accuracy. In order to reduce or avoid such interactions with the surroundings, the RF opaque member may be electromagnetically open to allow electromagnetic radiation escaping from it to spread over short distances, and be less susceptible to the surrounding. Thus, in some embodiments, the RF opaque member may have two ends, through which the material flows in and out of the RF opaque member, and theses ends (or at least one of them) may be electromagnetically open. Such an electromagnetic opening may be in the form of an RF transparent member or an RF absorbing member (e.g., member 422 illustrated in Fig. 4), generally referred to herein as electromagnetically obstructing member. The electromagnetically obstructing member may be sized and positioned so that changing the boundary conditions outside the apparatus does not change readings of the sensor by more than a predetermined degree. The degree itself may be predetermined according to the required accuracy and sensitivity of the sensor. Generally, higher sensitivity may require smaller susceptibility to changes in boundary conditions outside the apparatus, which may require a longer electromagnetically obstructing member. In some embodiments, the electromagnetically obstructing member may form a connecting member, or may be a portion of a connecting member for connecting the apparatus to the pipe, through which the material flows. The apparatus or a portion thereof, e.g., the RF opaque member, may replace a portion of the pipe, and be connected to the pipe with connecting members adapted to allow the material to flow fluently from the pipe to the RF opaque member (and/or in the opposite direction). Each of the connecting members may include the electromagnetically obstructing member.

[0084] An RF transparent member may function as an electromagnetic opening by allowing waves escaping from the RF opaque member to spread in all directions. An RF absorbing member may function as an electromagnetic opening by absorbing waves escaping from the RF opaque member. In both cases, there will be no significant interaction between the pipe in which the material flows to the sensor and from it, and the waves escaping from the RF opaque member. The meaning of "significant" may change in accordance with the required sensitivity and accuracy. In some embodiments, the electromagnetic opening, whether formed as an RF absorbing member, an RF transparent member, or in any other form, may cause the electric field to reduce along the electromagnetic opening by 2 orders of magnitude or more, for example by factor of 100, 200, 500, or any intermediate or higher factor. For example, the field near the connection between the electromagnetically obstructing member to the pipe (e.g., near flange 628 in Fig. 5 A), may be at least 100 times smaller than near the connection between the electromagnetically obstructing member to the RF opaque member (e.g., near flange 626 in Fig. 5A).

[0085] Returning to Fig. 1A, RF transparent conduit 104 may include an RF transparent material (e.g., a dielectric material). As used herein an RF transparent material may include any material that has a loss tangent smaller than 0.025, smaller than 0.01, or smaller than 0.005. Some examples of RF transparent materials may include galss, fiberglass, quartz, Teflon, various other polymers, and various ceramic materials.

[0086] In the following description conduit 104 is considered to be cylindrical and to have its axis of symmetry overlap with a symmetry axis (112) of a cylindrical RF opaque member 102, but other constructions are also possible. For example, the RF opaque member may have any shape, for example, it may be cylindrical, prismatic, rectangular, etc. In some embodiments, the RF opaque member may have the same symmetry as the conduit, for example, a cylindrical RF opaque member may be used with a cylindrical conduit, a rectangular RF opaque member with a rectangular conduit, etc. In some embodiments, the symmetry of the RF opaque member may differ from that of the conduit. In some embodiments, the conduit may be positioned along a longitudinal axis (e.g., symmetry axis) of the RF opaque member. In some embodiments, the conduit may run in parallel to a longitudinal axis of the RF opaque member, or it may be non-parallel to the said axis. In some embodiments, the conduit 104 has a diameter between one inch and eight inches; although, up to at least twenty-four inches is also contemplated. Smaller diameters, for example of 100 microns may also be contemplated. In some embodiments, the conduit may be adapted to handle flow rates of about lm/sec, so a one to two inch diameter conduit may fit to about 50-500 barrels of liquid (e.g., oil) per day, or an equivalent amount of gas (e.g., natural gas). Further, in some embodiments, conduit 104 may be capable of withstanding pressures of at least 50 bar, in some embodiments at least 250 bar. In some embodiments, conduit 104 may be capable of withstanding temperatures of at least 150°C, in some embodiments, at least 250°C.

[0087] In some embodiments, conduit 104 may be made of a material having a dielectric constant s_conduit that is the same as the dielectric constant of flowing material 105 under investigation s_materiai- Since s_materiai may depend on the property of the material, it is generally unknown. However, it may be known that s_materiai is expected to lie within a certain range. In some embodiments, s_conduit has a value inside that certain range. In some embodiments, it may be preferred to have a conduit with s_conduit in the lower half of the range, for example, if the range of values that the dielectric constant of the material may have is between 1.5 and 5, the conduit may be made of a material having a dielectric constant between 1.5 and 3.25, for example, 2, 2.2, 2.5, 3, etc. In a particular example, a conduit for crude oil (2 < s_materiai < 5) may be made of Teflon (s_conduit = 2.2).

[0088] In some embodiments, RF opaque member 102 may be open-ended, so material may flow freely in and out of RF opaque member 102 without requiring opening and closing doors or valves. The RF opaque member may support standing waves in the frequency range used for investigating the material. In some embodiments, the RF opaque member 102 may be a microwave cavity. It is noted, however, that the open ends may allow some of the radiation applied to RF opaque member 102 for investigating the material to escape from the RF opaque member.

[0089] In some embodiments, the sensor or an apparatus including the sensor may replace a portion of a pipe, through which the material flows. For example, the apparatus or the sensor may replace a portion of an oil pipe, through which oil flows from a well. Electromagnetic waves may exit the RF opaque member through its flow openings, and travel along the pipe. The readings of the sensor may be affected by the fate of such waves, for example, if the waves are disturbed outside the RF opaque member, this disturbance may affect the readings of the sensor. This way, the sensor may be sensitive to electromagnetic disturbances that occur away from the sensor. In some embodiments, this problem is coped with by isolating the sensor from the pipe so that electromagnetic waves going along the pipe diminish before they enter the sensor. This may be equivalent to a situation where electromagnetic waves going out of the RF opaque member diminish before they travel along the pipe. Such isolation may be obtained by introduction of an electromagnetic opening that may absorb or spread all radio frequencies to which the sensor is sensitive on their way out of or into the RF opaque member.

[0090] Detector 120 may be configured to detect electrical responses of RF opaque member 102 to incoming RF signals of various frequencies, and generate signals indicative of what it detected, so as to allow processor 130 to make use of the detected response. The range of frequencies that may be used to investigate the flowing material may be all above an inner cutoff frequency, of RF opaque member 102. The inner cutoff frequency may be defined as the lowest frequency at which RF fields may be excited in RF opaque member 102. RF radiation having frequencies lower than the inner cutoff frequency may decay in RF opaque member 102. The inner cutoff frequency depends of the inner dimension (e.g., diameter) of RF opaque member 102, and the flowing material 105 under investigation. The range of frequencies used to investigate the flowing material may be as broad as possible, since it is suggested that in some embodiments of the present invention sensitivity and/or accuracy may be improved by enlarging the number of modes excited in RF opaque member 102 during investigation. Nevertheless, frequencies below the inner cutoff may be omitted, since they are not expected to provide much information about the flowing material. In some embodiments, the frequency range used for investigating the material may be between 1.3 GHz and 4.7 GHz, between 1.8 GHz and 4.7 GHz, between 1.5GHz and 5.5. GHz, between 2GHz and 8GHz, between 500MHz and 1000 MHz, or any other portion of the microwave frequency range, that is between 300MHz and 300GHz. In some embodiments, lower frequencies (e.g., 10MHz to 300MHz) may be used, and the term "microwave" as used herein may include them too. In some embodiments, the frequency range used for investigating flowing material may span at least 1.5 octave or, in some embodiments, at least two octaves (i.e., the highest frequency is at least 2.8 times or at least four times higher than the lowest frequency). For example, in two octaves embodiments, if the lowest frequency is 1 GHz, the highest frequency is at least 4 GHz. In some embodiments, the frequency range may have a width (i.e., breadth) of at least 100% of the central frequency (i.e., the difference between the highest and central frequency is at least as large as the central frequency, and the ratio between the highest and lowest frequency is at least 3). For example, in such embodiments, if the central frequency is 2 GHz, the frequency range may be between 1 GHz and 3 GHz, or any other broader frequency range centered around 2 GHz.

[0091] The number of different frequency used for the investigation of the property of the material is usually more than 100 frequencies, and in some embodiments at least 500 frequencies, at least 1000 frequencies, or at least 1500 frequencies. The difference between two consecutive frequencies may be large enough to allow relatively fast measurements. Thus, the wish to have a lot of information may balance with the wish to get the information quickly, so in some embodiments broader frequency ranges (e.g., from 1.5 GHz to 6 GHz) are used at relatively sparse inter-frequency difference of, for example, 5 MHz, so that the total number of frequencies is about 900, and the frequency range is two octaves wide. In some embodiments, the inter-frequency difference is at least 3 MHz, at least 5 MHz, or at least 10 MHz. [0092] Detector 120 may be configured to send signal to processor 130. Detector 120 may be connected to processor 130 via wired or wireless communication. In some embodiments, processor 130 may be physically installed in proximity to detector 120 and RF opaque member 104. Alternatively, processor 130 may be remotely located and detector 120 may be configured to send the signals indicative of the detected electrical responses of the RF opaque member to incoming RF signals to processor 130, via remote communication (wired or wireless), for example, over the internet. In some embodiments, the detected signals may be partially processed by detector 120, prior to sending the signals to processor 130. For example, detector 120 may detect EM measurable parameters, such as voltage and current and may further calculate (e.g., digitally or analogically) the network parameters (e.g., s parameters, z parameters, input impedance zo) from the measured parameters. In some embodiments, the calculation may be carried out outside the detector, for example, by processor 130. Detector 120 may send the measured and/or calculated parameters to processor 130 for further analysis. Processor 130 may estimate properties of the flowing material using the signals received by processor 130 from detector 120.

[0093] The signals sent by detector 120 may be indicative of any RF signal coming from RF opaque member to feeds 106 and detected by detector 120 coupled to the feeds. The signals may include all the EM measurable parameters of an RF radiation. Such parameters may include, for example, network parameters (e.g., s parameters, z parameters, input impedance z₀), their magnitudes and/or phases, or any other parameter that may be indicative to relationships between electromagnetic waves going into the cavity and out of it, for example, Γ parameters (scalar or complex), dissipation ratios, etc.. In some embodiments, both magnitudes and phases of the parameters may be detected by detector 120. In some embodiments, investigation of the flowing material may be carried out using complex EM measureable parameters; yet, in some embodiments, magnitudes alone or phases alone are considered during the investigation. In some embodiments, the flowing material may be investigated using both phases and magnitudes of complex EM measureable parameters. In some embodiments, EM measureable parameters that are not complex (i.e., may be represented by real numbers) may be used for investigating the flowing material. Sensor 100 may include a plurality of feeds 106. In some embodiments, accuracy of the investigation may be higher with apparatuses having a larger number of feeds. For example, an apparatus with four feeds (As shown in Fig. 1A) may provide higher accuracy than a similar apparatus with 3 feeds, two feeds, or a single feed, and a sensor with a larger number of feeds, e.g., 9 feeds, may allow higher accuracy than a four- feed apparatus. The number of feeds may affect the number of modes that may be excited in the RF opaque member, and may also affect the spatial distribution of local intensity maximums of the excited modes. The local intensity maximums may be important, since the readings of the detector may be more strongly affected by properties of the material in the vicinity of such maximums than away of such maximums.

[0094] Excitation of each mode generates in the RF opaque member a typical electrical field distribution (also referred to herein as a field pattern). The field pattern may have one or more local extreme points, at which the field amplitude is at minimum or maximum, and the field intensity is at maximum. Having more feeds may allow exciting in the RF opaque member modes having their local intensity maximums more widely distributed inside the RF opaque member. For example, each mode is most easily excitable by a feed that lies at an intensity maximum of the field pattern associated with the mode. Accordingly, having feeds in many different places may facilitate exciting in the RF opaque member modes having their intensity maximums at many different places. It is suggested herein that wide spread of local intensity maximums within the investigated material may enhance the accuracy.

[0095] In some embodiments, accuracy may be optimized by exciting in the RF opaque member such modes that their local intensity maximums cover the entire volume of the material under investigation. For example, each local intensity maximum may be associated with a volume around the maximum, at which the field intensity is larger than half the intensity at the maximum. In some embodiments, the volumes associated with all the local intensity maximums of all the modes excited in the RF opaque member cover the entire volume of the material under investigation flowing inside the cavity. The volume of flowing material 105 under investigation is the volume in the void defined by the walls of RF transparent conduit 104 inside RF opaque member 102. In some embodiments, optimal locations may be determined for feeds of a given number by calculating, e.g., from a simulation, for each set of locations, the total volume of the local intensity maximums of the field patterns excitable in the RF opaque member by the feeds at the tested locations. A location set at which this volume is maximal among the tested sets may be used in practice to maximize the coverage of the material under investigation with local maximums.

[0096] In some embodiments, one or more of the feeds 106 comprises a radiating element 108, outside RF opaque member 102 and a waveguide 110 configured to guide waves from radiating element 108 to the RF opaque member. Having radiating elements 108 outside RF opaque member 102 may reduce direct coupling between the feeds 106. In some embodiments, radiating element 108 ends outside RF transparent conduit 104, to protect the radiating element form the material flowing inside the conduit. In some embodiments, radiating element 108 may have an end 108', through which microwave radiation may emanate. It is noted that the term radiating element refers to an element that radiates RF radiation into the RF opaque member. A radiating element may be an antenna, or a radiating part of an antenna. In some embodiments, each radiating element is connected to a detector. In some embodiments, each radiating element is connected to its own detector, and in some embodiments wo or more radiating elemenets are connected to the same detector. The detector is configured to detect RF radiation received by the radiating element from the RF opaque member through the radiating element. At least one of the radiating elements is also connected, or at least connectable, to an RF source, that supplies RF energy to the radiating element. This RF energy may cause the radiating element to radiate into the RF opaque member. The at least one radiating element may be connected to the RF source through a switch that may disconnect between the source and the radiating element. In such embodiments, when the switch disconnects the radiating element from the source, they may be said to be disconnected, but still connectable. In some embodiments, the wall of RF opaque member 102 may have a feed opening 102' for receiving radiation from feed 106. Feed opening 102' may fit the outer shape of waveguide 110. In some embodiments, the distance between end 108' and feed opening 102' may be λ/2, wherein λ is the wavelength, inside waveguide 110, of the lowest frequency used for investigating the material (i.e., the lowest frequency of the RF radiation exciting modes in the RF opaque member). Waveguide 110 may be filled with a dielectric material having a dielectric constant s_waveguide. In some embodiments, the filling of waveguide 110 may be chosen to ensure that the cutoff frequency of waveguide 110 is not higher than the inner cutoff frequency of RF opaque member 102. In some embodiments, the physical dimensions of waveguide 110, e.g., its diameter, and the dielectric constant Swaveguide are such that the diameter of the waveguide is about half that of the inner diameter of RF opaque member 102, or less, for example, the ratio between the diameters may be between 0.25 and 0.5. Some values of dielectric constants for the filler of the waveguide may be, for example, 6, 9, or 12.

[0097] In some embodiments, feeds 106 may be isolated from each other. It was found by the inventors that better isolation may bring about higher accuracy. The inter-feed isolation may vary across frequencies, and in some embodiments, frequencies at which the isolation is below a threshold may be discarded, for example, they may be disregarded by processor 130 when the property is determined. Minimizing inter-feed coupling may be another way to improve accuracy of the apparatus. Thus, in some embodiments, the isolation between the feeds is such that less than 10% of power entering the RF opaque member through one feed exits the RF opaque member through another feed. In some embodiments, the isolation between the feeds is such that less than 10% of power entering the cavity through one feed exits the RF opaque member through all the other feeds together. In some embodiments, these levels of isolation may be kept only across some of the frequencies, for example, across half or more, 75% or more or 80% or more of the frequencies used for determining the value of the property. In some embodiments, 'frequencies used' may include only frequencies used by processor 130 for determining the property. In some embodiments, 'frequency used' may include all the frequencies at which radiation is fed into cavity 102 for the investigation.

[0098] In some embodiments, inter-feed isolation may be enhanced by properly spacing and/or orienting the feeds. For example, in some embodiments, at least one of the feeds is inclined in respect of a symmetry axis of the RF opaque member. This may be exemplified in Fig. 1 A by feeds 106 being inclined in respect of symmetry axis 112. One way of optimizing inter-feed isolation according to some embodiments is discussed below with reference to Fig. 2A in the context of inclined feeds. The inclination angle a may be, for example, between 20° and 70°, for example, 30°, 40°, 45°, 50°, 60°, or any other intermediate angle. One or more of the feeds may be perpendicular to the axis (e.g., a may be 90°, optionally 90°±10°). Inclined feeds may be advantageous over perpendicular feeds in that they may allow exciting, by a single feed, modes of different types, for example, TE, TM, and quasi-TEM. [0099] In some embodiments, the feeds may include one or more pairs of parallel feeds. Parallel feeds may be feeds, each having a symmetry axis, wherein the symmetry axes of the feeds are substantially parallel to each other. For example, the angle between them may be smaller than 10°, preferably around 0°. In some embodiments, feeds with parallel symmetry axes may be positioned such that their symmetry axes overlap. However, to improve decoupling between the feeds it may be preferable to have the parallel feeds with non-overlapping symmetry axes, e.g., inclined parallel feeds that do not overlap. Such two pairs of parallel feeds with non-overlapping symmetry axes are illustrated in Fig. 1A, where feeds that lie diagonally to each other are parallel to each other. In some exemplary embodiments, two of the feeds are equally inclined with respect to the axis of symmetry of the RF opaque member, (e.g., one extends at 40° to the symmetry axis, and the other extends at 140° to the symmetry axis) and are spaced apart from one another such that electromagnetic radiation propagating along an axis of symmetry of one feed and reflected from an inner face of the RF opaque member propagates out of the RF opaque member through the other of the two feeds. The equally inclined feeds may lie on a line parallel to the symmetry axis of the RF opaque member. In some embodiments, the equally inclined feeds may lie off set from one another, for example, on a line non parallel to the symmetry axis of the RF opaque member.

[00100] Fig. IB is an isometric view of an exemplary sensor 100 according to some embodiments of the invention. Fig. IB shows an RF opaque member 102 with four feeds 106. The feeds shown in Fig. IB are all on the same plane. Each feed 106 is shown to include a radiating element 108 and waveguide 110. Radiating element 108 may penetrate into waveguide 110, but this is not seen in the present view. Also shown in the figured are the flowing material to be investigated (105) and a dielectric conduit 104, within which material 105 may flow. In some embodiments, the dielectric conduit fills the entire RF opaque member 102, other than space left for the material to be investigated, as shown diagrammatically in Fig. 1 A.

[00101] Fig. 1C is an isometric view of an exemplary sensor 100 according to some embodiments of the invention. In Fig. 1C RF opaque member 102 with nine feeds (106) is shown. The feeds are arranged in groups of three. The group in the middle comprises feeds that are on a plane perpendicular to the symmetry axis of conduit 104. The groups at the edge, each comprises three pairs of feeds, and each pair is on a plane inclined to the symmetry axis of conduit 104 and non-parallel to any of the other two planes. Orienting the feeds on such non-parallel planes may increase inter-feed isolation, and thus, in some embodiments, may enhance accuracy.

[00102] Some embodiments, such as those depicted in Figures 1A-1C may include a pair of inclined parallel feeds. The parallel feeds may be coplanar, for example, the central symmetry axis of the feeds may lie on the same plane. In some embodiments, the central symmetry axis of the feeds may be parallel or substantially parallel (e.g., be inclined one in respect of the other by 10° or less, 5° or less, or 2° or less. In some embodiments, the parallel axes do not overlap, so that despite of the feeds being parallel, a ray going in straight line along the symmetry axis of one of the feeds will not enter the other feed.

[00103] In some embodiments, measurement of a property of the flowing material using sensor 100 may include generating a model useful to identify one or more properties of a material flowing in the sensor. Generating the model may include flowing materials of known properties (e.g., known composition) in the sensor at a controlled flow velocity and temperature. During the flow of each of the materials in the sensor, RF spectrums may be from the sensor, and each such spectrum may be associated with the properties of the material and conditions (e.g., flow rate and temperature), under which each spectrum was collected. This association may then be mathematically analyzed to find spectral features that correlate with the known properties and/or conditions. This way, a model that tells the material properties and flow conditions based on the measured RF spectrums may be generated. The estimation ability of the model may be tested on samples of known properties, and once found satisfactory, the model may be used to estimate material properties and flow conditions of other samples, in which the properties and conditions are not known (also referred to herein as unknown samples). To tell the properties of an unknown sample, RF spectrums of the unknown sample may be collected, e.g., by inputting an input RF signal (e.g., a CW signal) from source 120 through one of feeds 106 into RF opaque member 102. In response, some RF signals (which may be referred to as feedback signals) may be received at feeds 106 and detected by detector 120. Detector 120 may send to processor 130 signals indicative of some values representing the received feedback signals (e.g., the feedback signal's amplitude, phase, the relation between the amplitude of the feedback signal and the amplitude of the input signal, the square of that ratio, a phase of the feedback signal, a phase difference between the input signal and the input signal, etc.). Processor 130 may store the values received from detector 120, associated with the frequency of the input signal, at which each feedback signal was received. Such association may be referred to as an RF spectrum. Processor 130 may also store the model obtained with the known samples, and apply the model to the recently collected spectrums to provide estimates of the properties of the material that flowed in the sensor when the spectrums were taken. Thus, according to some embodiments, a method of estimating properties of a flowing material may include the following steps, summarized in the flowchart of Fig. 8. In step S2, samples of known compositions are prepared and flowed through sensor 100 at controlled flow conditions, e.g., controlled flow rate and temperature. During the flow, spectrums indicative of the dielectric constant of the flowing material at various frequencies may be measured, and saved.

[00104] In step S4, a model is generated, correlating features of the spectrums with the properties of the materials that flowed in the sensor when these spectrums were taken.

[00105] In step S6, the model is stored in a memory accessible to processor 130 of sensor 100. For example, the model may be stored on a memory residing in sensor 100 (e.g., in processor 130), or on a memory remote from sensor 100, with which sensor 100 may communicate, for example, through a communication network. Sensor 100 used in steps 802 and 804 and sensor 100 used in steps S6 forward may be two different duplicates of the same sensor.

[00106] In step S8, sensor 100 storing the model may be taken to the field, at which unknown samples are to be measured. For example, if the model is for estimating fat content in milk the sensor may be taken to a dairy, and if the model is for estimating gas fraction in crude oil, the sensor may be taken to an oil field.

The sensor may be then installed in the field, for example, it may be used to replace a portion of an oil-duct in an oil field, a milk pipe in a dairy, etc.

[00107] In step S10, sensor 100 may be used to collect spectrums from unknown samples.

[00108] In step SI 2, the model may be applied to the spectrum collected in step

S10, to estimate the properties of the unknown samples.

[00109] In some embodiments, when sensor 100 (or an apparatus that includes sensor 100) replaces a portion of a pipe which carries the flowing material under investigation, sensor 100 may be placed such that the material flowing in the pipe flows fluently through the sensor and the sensor may be operated to determine the property. For example, sensor 100 may replace a portion of a pipe carrying crude oil from an oil well, or a portion of a milk pipe in a dairy. In absence of an electromagnetic opening, the readings of the sensor may be sensitive to its surrounding, so that at different installations the same sensor might provide different readings when the same material flows therein. This may result in reduced reliability of the sensor's readings. The electromagnetic opening may improve the reliability in the sensor by making the sensor insensitive to the surrounding in which it operates, but only to the material flowing therein.

[00110] In some embodiments, the sensor may be located before or after a bend in the pipe. The bend may change the boundary conditions outside the apparatus, in comparison to the boundary conditions under which the model was generated. For example, if the model was generated based on spectrums collected when there was no bend, the estimations of the properties of the material may be inaccurate or even wrong because of the difference in boundary conditions considered in generating the model and in using the model to estimate the properties in the field

[00111] Similarly, a valve near the sensor may cause the sensor to estimate composition of a material differently when the valve is open or close, because the valve position may affect the boundary conditions outside the apparatus. These problems may be coped with, in some embodiments, by adding to the sensor an electromagnetic opening, for example, in the form of an electromagnetically obstructing member, as described below in connection with Fig. 4.

[00112] In some embodiments, the inclination angle a (see Fig. 1A) and the distance X between two inclined feeds may be such that there is high coupling between the feeds at one particular mode, and low coupling at all other modes. One way to achieve this effect is illustrated in Fig. 2A.

[00113] Fig. 2A is a diagrammatic illustration of an RF opaque member 202 with two feeds 206a and 206b. For simplicity, a conduit for the material is not shown. Similarly, additional feeds are not shown for the sake of simplicity. The diameter of RF opaque member 202 is marked as D. To improve isolation between the feeds it may be useful to ensure that electromagnetic radiation propagating in feed 206a and reflected from the inner wall of RF opaque member 202 (e.g., ray 240) finds its way towards the other feed 206b. A mode having a local intensity maximum at the meeting point of ray 240 with the inner wall may suffer from strong coupling between the feeds, but other modes may enjoy improved inter-feed isolation. To estimate a proper distance X between the feeds, one may use Snell's low, according to which: wherein θ = 90°— a ; and θ₂ is defined in Fig. 2.

Using basic trigonometry it is easily verified that tan θ₂ = -^;

and after using Snell's law and rearranging, it may be shown that

Wherein

[00114] Thus, in some embodiments, the distance between the feeds X and the inclination angle a obey the above relationship. Some RF opaque members according to the present invention may have an inner opening-dimension defining an opening cutoff frequency, as discussed in more detail in reference to Figs. 2B, 2C, and 2D. In some embodiments, source 115 is configured to supply RF energy at frequencies higher than the opening cutoff frequency. For example, the range of frequencies used for investigating the material may be from 1.3 GHz and 5 GHz, and the opening cutoff frequency may be 2.25 MHz. In some embodiments, in operation, the controller controls the source to supply to the RF opaque member through the feeds various frequencies . These various frequencies may be used for investigating the properties of the flowing material.

[00115] Some RF opaque members according to the present invention may have two flow openings, one at each side of the RF opaque member. Each of the flow openings may have an opening-dimension. The opening's dimension and the material flowing in the RF opaque member, may define an opening (e.g., end) cutoff frequency, such that the various frequencies include at least one frequency higher than the opening cutoff frequency. It is noted, that while the cross-section available for material flow in and out the RF opaque member may be smaller than the flow opening, for example, if the inner diameter of the RF transparent conduit is smaller than the opening's dimension. Electromagnetic (EM) waves having frequencies higher than the opening cutoff frequency may either enter the RF opaque member or exit the RF opaque member via the opening. EM waves entering the RF opaque member may affect or change the boundary conditions at the opening, thus may change the modes excited in the RF opaque member. Changing the boundary conditions at the opening may alter the response of the RF opaque member and may change the readings of the sensor.

[00116] Reference is made to Figs. 2B-2D that are diagrammatic illustrations of exemplary RF opaque members according to some embodiments of the invention. One example of an RF opaque member is illustrated in Fig. 2B. An RF transparent conduit 214 may be located within RF opaque member 210. Conduit 214 may be configured to direct flowing material 105 through RF opaque member 210. Conduit 214 may have substantially the same dielectric constant as flowing material 105. For example, a conduit for crude oil (2 < s_materiai < 5) may be made of Teflon (s_conduit = 2.2). RF opaque member 210 may have a flow opening 216 having an opening dimension d that may define an opening cutoff frequency. The opening cutoff frequency may also depend on the dielectric constant of dielectric conduit 214 and that of flowing material 105. Radiation at frequencies higher than the opening cutoff frequency defined by opening 216 may propagate in and out the opening. Radiation at frequencies below the opening cutoff frequency defined by opening 216 may decay on their way in or out the RF opaque member through the opening. Thus, measurements made at frequencies higher than the cutoff may be sensitive to boundary conditions farther from the opening of the RF opaque member than measurements made at frequencies lower than the opening cutoff frequencies.

[00117] The frequencies used for analyzing the flowing material may include at least one frequency, and at times a significant amount of the frequencies (e.g., 10%, 25%, 50%>, or more of the frequencies) are above the opening cutoff frequency, and thus may be sensitive to electromagnetic disturbances away from the opening. Frequencies below the opening cutoff frequency may be sensitive to electromagnetic disturbances only at shorter distances from the opening, because they tend to decay. One way to make the sensor relatively insensitive to electromagnetic conditions outside the RF opaque member (e.g., along the pipe feeding the RF opaque member with the flowing material) is to use only frequencies below the opening cutoff frequency. However, enlarging the number of frequencies may facilitate accuracy and sensitivity of the sensor.

[00118] The dimension d of opening 216 may be substantially similar to the inner dimension of RF opaque member 220. Alternatively, the dimension of the opening may be smaller than the inner dimension of the RF opaque member. In an exemplary RF opaque member having a cylindrical shape, the inner dimension may be the inner diameter of RF opaque member 220 and the opening dimension may be the opening diameter of opening 216.

[00119] Each of exemplary RF opaque members 220 and 230 illustrated in Figs. 2C and 2D has at least one opening having an opening dimension D (e.g., a diameter) smaller than the inner dimension d (e.g., a diameter) of the RF opaque member. The inner dimension d of RF opaque member 220 is larger than the opening dimension D of an opening 226. The dimension of opening 227, on the other hand, is the same as the opening dimension D. The inner dimension d of RF opaque member 230 is larger than opening dimension D of openings 236 and 237. Opening dimension d may be at least as large as the inner dimension of conduit 214 to avoid any disturbances to the flow of flowing material 105, or may be larger than the inner dimension of conduit 214, as illustrated, for example, in Fig. 2B. Opening dimension D may be between the inner dimension of the RF opaque member d and the inner dimension of the RF transparent conduit.

[00120] In some embodiments, if EM radiation travels in a pipe connected to the apparatus such EM radiation may reach the sensor (e.g., sensor 109) and change its readings. To minimize such influence on the readings of the sensor, it may be useful to design the RF opaque member with the smallest possible opening, so that the cutoff frequency is as high as possible. Nevertheless, some embodiments described herein allow working with frequencies higher than the cutoff frequency for analyzing the properties of the flowing material. This may be achieved without compromising the electromagnetic isolation between the sensor and the pipe connected to it, for example, by adding to the sensor an electromagnetically obstructing member that obstructs the RF flow between the pipe and the sensor without obstructing the material flow between them.

[00121] Fig. 3 is a flow chart of a method 300 of determining a value of a property of a flowing material that flows in a conduit inside an RF opaque member (e.g., a microwave cavity) according to some embodiments of the invention. Method 300 may include a step a number of feeds, as discussed above. For example, one (or more) of the feeds may include a radiating element outside the RF opaque member and a waveguide configured to guide waves from the radiating element to the RF opaque member. Exciting the multiple modes may include, for example, transmitting into the RF opaque member microwave radiation (e.g., in the form of microwave signals) at various frequencies. If multiple feeds are provided, exciting the multiple modes may include transmitting the waves through different ones of the feeds. Generally, it may be said that the different modes may be excited by transmitting to the RF opaque member RF radiation at different excitation setups, wherein each excitation setup is defined by the transmitting feed and by the transmitted frequency. In some embodiments, when waves are transmitted simultaneously through a plurality of feeds, at a common frequency, and at controlled phase differences between the feeds, the excitation setup may be further defined by the phase differences. If other parameters that may affect the field pattern excited in the RF opaque member are also controllable by apparatus 100, the excitation setups may be further defined by them.

[00122] In exemplary embodiments of the disclosure, exciting a number of modes is by applying to the RF opaque member RF radiation at a plurality of excitation setups. In some embodiments, each two of the excitation setups differ from one another in at least one of a frequency or a feed, through which RF radiation is fed to the RF opaque member to obtain the excitation. By applying excitation to different feeds, through their respective ports, and at different frequencies, excitation of various modes can be achieved.

[00123] In some embodiments, excitation of the modes includes exciting a number of modes that is larger than the number of the feeds. For example, if the feeds are inclined as described above, and each feed excites in the RF opaque member one mode of each type (e.g., TE, TM, and quasi-TEM), the number of modes may sometimes be three times larger than the number of feeds.

[00124] Method 300 may further include step 304 of detecting parameters indicative of electrical response of the RF opaque member to the excitation of the modes in the RF opaque member. As discussed above, such parameters may include network parameters (e.g., s parameters), gamma parameters, or any other electrical response indicator. It is noted that in some embodiments, for example, where the various feeds are decoupled, parameters indicative of radiation transfer from one feed to another (e.g., Sij, ijj) may be less informative than parameters indicative of reflections back to the emitting feeds (e.g., Sii or Γ parameters also known as gamma parameters). Accordingly, in some embodiments, the parameters indicative of electrical response of the RF opaque member to RF radiation fed to the RF opaque member may include a ratio between power measured to go towards the RF opaque member at a given feed, and power measured to get back from the RF opaque member towards the given feed. If the feeds emit each at a time, this ratio may be a diagonal s parameter; if the feeds emit at overlapping time periods, this ratio may be a Γ parameter. In some embodiments, only magnitudes of the S or gamma parameters are considered, while in other embodiments, the phases of the parameters are also considered.

[00125] Finally, method 300 may include step 306 of determining the value of the property based on the detected parameters. This may include, in some embodiments, comparing electrical response indicators (either as measured, or after further processing, e.g., combination as discussed above) with values obtained from reference materials during a training state. In some embodiments, the comparison may include usage of a kernel method, for example, as support vector machine.

[00126] Some embodiments of the invention may include RF-based flow rate measurements. The measured flow rate may be of a foreign body (e.g., gas bubble) flowing within a material. The material itself may be flowing or stationary. In the latter case, the foreign body may be moved in the stationary material, for example, by ultrasonic waves. The foreign body may have a dielectric constant different from that of the material, so it reflects RF radiation to a different extent. Some examples of foreign bodies may include gas bubbles in a liquid material, oil droplets in water, solids in liquids, etc. In some embodiments, measuring the flow rate may include comparing frequencies of signals transmitted at one point along the flow path to frequencies received at another point down the flow path. Due to the Doppler Effect, the frequency of the received signal may be shifted in respect to the frequency of the transmitted signal by a degree indicative of the flow rate.

[00127] In some embodiments, the measurements may take place inside a microwave cavity. The microwave cavity may include metallic walls encasing a dielectric conduit, along which the material may flow. Since tangential electric field components tend to vanish in the vicinity of the opaque (e.g., metallic walls), such as walls of microwave cavities, foreign bodies moving near the walls of the cavity may be hard to detect. The dielectric conduit may limit the flow of the flowing material to regions where the distance from the wall is large enough to ensure that the electrical field does not vanish within the material due to closeness to the metallic wall. Thus, in some embodiments, the thickness of the conduit is at least 1/4 a wavelength of the RF radiation used for measuring the flow rate. The said wavelength may be a wavelength inside the dielectric material constituting the conduit

[00128] In some embodiments, the signals are transmitted through a single radiating element at a time. In some embodiments, the signals (e.g., RF signals) are transmitted through multiple radiating elements at overlapping time periods and at the same frequency. The multiple transmitting radiating elements may be positioned at different points along a perimeter of the microwave cavity, and at a common distance from an end of the flow path of the foreign body within the conduit. In some embodiments, the signals may be received by two or more radiating elements.

[00129] The comparison may be of the signal, or of the electrical response of the cavity to the signal. The dielectric response may be expressed, for example, by the network parameters of the cavity with the material and foreign body flowing therein. In some embodiments, values of network parameters may be used for the measurements. For example, the above-mentioned frequency shift may be detected as a time varying phase shift in a transfer parameter (Sij, ijj). More generally, when a foreign body is moving (e.g., flowing), the electrical response of the cavity with the moving foreign body will vary over time, and this variation may be used to estimate the flow rate.

[00130] In some embodiments, measurements may be taken at a plurality of frequencies. This may be advantageous in that different frequencies may excite in the flowing material different modes. The sensitivity of the measurement may depend on the field intensity at the immediate location of the foreign body. Since different modes may have field maximums at different locations, different frequencies may allow sensitive measurements of bodies that flow at different portions of the conduit. Thus measurements taken at a plurality of frequencies may be sensitive to foreign body motion at many different portions of the conduit, and in some embodiments, practically everywhere within the conduit between the transmitter and the receiver. In some embodiments, differing modes or differing field patterns may be excited with a single frequency. For example, the same frequency may be emitted through differing radiating elements, resulting in the excitation of differing field patterns in the conduit. In another example, two or more of the radiating elements may concurrently radiate at the same frequency and at differing phase differences between them, resulting in excitation of a plurality of field patterns, and thus increase the sensitivity of the measurement method. The field patterns may include two or more field patterns that are significantly different from each other. In some embodiments, two field patterns may be considered significantly different from each other if a position with a low electric field (e.g., smaller than 20% of the maximal electric field) of the first field pattern has a high electric field (e.g., larger than 50% of the maximal electric field) within the second field pattern.

[00131] In some embodiments, measurements may be carried out based only on signals having intensity above a threshold. The threshold may be set based on the noise known to exist in the system. For example, in some embodiments, only signals having a signal to noise ratio of at least 2, at least 3, at least 4, etc., may be taken into consideration. In some embodiments, the noise level may be detected during operation, and the threshold may be adjusted online to noise existing in the system at every instance. For example, the noise may change from time to time and the threshold may be automatically adjusted accordingly. Such automatic threshold adjustment may be facilitated by receiving RF radiation from a region within the conduit, which is not accessible to foreign bodies, or much less accessible than most other portions of the conduit. Thus, every signal received from such a region may be treated as noise, and the threshold may be automatically adjusted based on readings from such a non-accessible region. Such automatic threshold may also be determined according to noise level within a Doppler frequency (up to 2v/ λ) in which there are no signals from foreign bodies due, for example, to the limit present on the maximal flow speed of the foreign body which is typically the flow rate of the material in which the foreign body flows. This may be possible since the flow rate is proportional to the maximal Doppler frequency induced by the foreign body.

[00132] In some embodiments, the maximal size and the minimal flow velocity of the foreign body may be expected to have are known, and, automated threshold adjustments may be set by comparing Doppler signal reflections at times before or after the foreign object has passed through the conduit, and during the passing of the foreign object between the radiating elements. The signal to noise ratio to be crossed by a signal may be set before measurements begin. This ratio may be, for example between 2 and 4. In general, the larger is the ratio - smaller number of signals is taken into account, and more false negative and less false positive readings may be expected.

[00133] In some embodiments, the amount and volume of the foreign objects may be estimated by measuring the strength of a Doppler signal. The Doppler signal may be correlated to the amount and volume by a proportionality-constant. In case the foreign object is to be detected on the background of a non-homogenous flow, the Doppler signal from each location in space may be calculated separately thereby providing the ability to perform detection by comparing the Doppler signal from each small spatial volume to the Doppler signal from its neighboring volumes. Calculation of signals and their origin in space may be accomplished by coherently summing reflections from different frequencies and radiating elements with appropriate weights, such that each weight set emphasizes contributions to the Doppler signals from a different location in space.

[00134] In some embodiments, an apparatus (e.g., apparatus 100) for detecting phase- composition of a multi-phase material (e.g., crude oil) may include RF-based flow rate detection (e.g., by measuring Doppler signals). In some embodiments, it may be assumed that the different phases of the multi-phase material (e.g., water, gas and oil of a crude oil) are flowing in unison and thus the flow rate of the multi-phase material is identical or similar to the flow rate of the gas. The flow rate of the multi-phase material may be detected by detecting a flow rate of a gas flowing within the multi-phase material (e.g., crude oil). In some embodiments, the gas may be treated as the foreign object to be detected (e.g., by Doppler means as discussed above).

[00135] In some embodiments, Doppler detection (for example: as discussed above) may be used for detecting foreign object in a flowing material: e.g., for detecting undesired objects flowing in the material - for example: in food industry - it may be desired to detect foreign objects in a food being processed (e.g., flowing milk, juices, creme etc.). In some embodiments, the size of the detected foreign object may be in the range of: mm3 (e.g., metal balls or glass/plastic beads having diameter of 2-6mm, e.g., 3mm). In some embodiments, once the foreign object is detected - an alert may be sent to the operator at the factory such that the foreign object may be removed.

[00136] In some embodiments, in order to improve the accuracy of the reading of the senor, the sensor may include an electromagnetic opening at one end of the sensor, or at both ends of the sensor. The electromagnetic opening may be formed as an electromagnetically obstructing member, for example, an RF transparent member or an RF absorbing member. For example, an electromagnetically obstructing member may be attached and/or connected to a flow opening of the RF opaque member, so that sensitivity of the sensor to changes in the boundary conditions away from the sensor along the pipe feeding it with the flowing material is reduced. In some embodiments, reduction in sensitivity of the sensor to changes in boundary conditions away from the sensor may be achieved by introducing an electromagnetic opening at the edge of the sensor. Such electromagnetic opening may let any RF radiation propagating towards the sensor to spread out before reaching the sensor. The electromagnetic opening may similarly let any RF radiation propagating from the sensor out, to spread out before being significantly affected by the boundary conditions outside the sensor. The electromagnetic opening may take a form of an RF transparent member. The RF transparent member may be sized and positioned so that changing the boundary conditions outside the apparatus or at an end thereof does not change the readings of the sensor by more than a predetermined degree. The end of the apparatus may be defined as the side of the RF transparent member (or any other electromagnetic opening) that is not connected to the sensor (e.g., the side that connects to a pipe supplying the flowing material). EM radiation traveling in the pipe that supplies the flowing material may "spread out" before reaching the sensor. Similarly, EM radiation that escapes from the RF opaque member may spread out before being affected by boundary conditions outside the apparatus. EM radiation traveling to the sensor or away from the sensor may include EM waves at frequencies higher than the opening cutoff frequency (e.g., openings, 216, 226, 236) and may travel long distances if not stopped. One way of stopping this radiation at the footstep of the sensor is letting it spread out, e.g., by an RF transparent member or an RF absorbing member. The RF transparent/absorbing member may provide an electromagnetic obstruction between the pipe and the sensor.

[00137] Without being bound to theory or to the following explanation, one may understand the effect of the opening as if it prevents the electromagnetic radiation escaping from the sensor from being reflected back from the pipe (e.g., if the pipe is made from RF reflective material) towards the sensor by allowing it to spread around in all directions, so the portion spreading back into the sensor is negligible. Still without being bound to theory, the effect of an RF absorbing member may be explained as if it absorbs much of the RF radiation going out of and into the sensor, so the portion that finds it way back to the sensor is negligible.

[00138] Another source for EM radiation that may have to be obstructed to isolate the sensor from uncontrolled disturbances may be an external electronic device that is attached or assembled in the pipe, for example, when the sensor is used in food and beverage industry, and additional sensors may be installed near sensor 100. Such an external electronic device may radiate EM energy that if includes frequencies higher than the opening cutoff frequency, may affect the readings of the sensor.

[00139] Reference is made to Fig. 4 that illustrates an exemplary apparatus (420) for determining a value of a property of a flowing material that flows through the apparatus. Apparatus 420 may include a sensor 100 and an electromagnetically obstructing member 422. Sensor 100 may include an RF opaque member configured to allow the flowing material to flow through the RF opaque member (e.g., RF opaque member 102, 210, 220 and 230). Apparatus 420 may also include a detector (not illustrated) such as detector 120 configured to detect electrical responses of the RF opaque member to incoming RF signals of various frequencies, and generate signals indicative of the detected electrical responses.

[00140] Electromagnetically obstructing member 422 may take the form of an RF transparent member, which may provide open boundary conditions at the end of the RF opaque member. RF transparent member 422 may be sized and positioned so that changing the boundary conditions outside apparatus 420 does not change the readings of sensor 100 by more than a predetermined degree. RF transparent member 422 may be positioned adjacent to the opening (e.g., opening 216, 266, 236) of the RF opaque member that allows the material to flow into and out of the RF opaque member. The size (e.g., length, diameter, etc.) of RF transparent member 422 may be such that most of the RF energy going into and away of the RF opaque member may escape through RF transparent member 422 to the surrounding of the apparatus. This way, readings of the sensor will be insensitive to electromagnetic disturbances outside the apparatus (e.g., along the pipe) even at frequencies higher than the opening cutoff frequency. Frequencies below the opening cutoff may decay upon escape from the RF opaque member even in the absence of an electromagnetic opening such as RF transparent member 422, and therefore, at such frequencies, the sensitivity to electromagnetic disturbances far away from the apparatus may be small even in absence of the RF transparent member. For example, to limit the effect of electromagnetic disturbances away from the apparatus to no more than 1% of the sensor's precision at frequencies higher than the opening cutoff, the length of the RF transparent member may be at least 10 times larger than the inner radius of the dielectric conduit. More generally, the effect of the EM disturbances on the accuracy of the sensor's reading is inversely proportional to the square of the ratio R/r, where R is the length of the RF transparent member, and r is the radius of the dielectric conduit, inside which the material flows inside the RF opaque member.

[00141] In some embodiments, electromagnetically obstructing member 422 may take the form of an RF absorbing member. RF absorbing member 422 may be sized and positioned so that changing the boundary conditions outside apparatus 420 does not change the readings of sensor 100 by more than a predetermined degree. RF absorbing member 422 may be positioned adjacent to the opening (e.g., opening 216, 266, 236) of the RF opaque member that allows the material to flow into and out of the RF opaque member. The size (e.g., length, diameter, etc.) of RF absorbing member 422 may be such that most of the RF energy going into and away of the RF opaque member may be absorbed in a wall of RF absorbing member 422. This may be achieved, for example, by using as an RF absorbing material a hollow tube, the inner surface thereof being coated with RF absorbing coating that absorbs the frequencies used by the apparatus for investigating the property of the material. This way, readings of the sensor will be insensitive to electromagnetic disturbances outside the apparatus (e.g., along the pipe) even at frequencies higher than the opening cutoff frequency.

[00142] RF transparent member 422 may include any material that is transparent in the RF range, for example, glass, ceramics, fiberglass, or Polytetrafluoroethylene. RF absorbing member 422 may include an RF absorptive coating, e.g., a microwave absorbing coating manufactured by MWT materials Inc.

[00143] Electromagnetically obstructing member 422 and the RF opaque member (e.g., RF opaque member 102, 210, 22 and 230) may be configured so that material flowing through the RF opaque member continues flowing through the electromagnetically obstructing member or vice versa. In some embodiments, the electromagnetically obstructing member and the RF transparent conduit located within the RF opaque member may have substantially the same inner dimension (e.g., diameter) and may be coaxially placed with respect to each other, such that the flowing material may flow unobstructed from the RF opaque member to the electromagnetically obstructing member or vice versa, through the apparatus.

[00144] In some embodiments, the apparatus may include two electromagnetically obstructing members 422, one at each side of the RF opaque. In some embodiments, the two electromagnetically obstructing members may include two RF transparent members, two RF absorbing members, or one RF absorbing member and one RF transparent member. In some embodiments, the RF opaque member and electromagnetically obstructing members 422 are so configured, that material flowing through one electromagnetically obstructing member continues flowing through the RF opaque member, and from the RF opaque member through the other electromagnetically obstructing member. The electromagnetically obstructing members and the RF transparent conduit located within the RF opaque member may have substantially the same inner dimension (e.g., diameter) and may be coaxially placed with respect to each other, such that the flowing material may flow unobstructed along the pipe that includes the apparatus.

[00145] In some embodiments, apparatus 420 may be installed to replace a portion of a pipe carrying the flowing material under investigation, so that material flowing in the pipe flows fluently through the apparatus. Apparatus 420 replacing a portion of the pipe may be operated to measure a property of the material flowing in the pipe, using for example, sensor 100 included in the apparatus. For example, apparatus 420 may replace a section of a milk pipe in a diary, or a section of an oil pipe in an oil well, or a section of a waste water pipe in a sewage pipe, or the like.

[00146] An exemplary apparatus for determining a value of a property of a flowing material, having two electromagnetically obstructing members according to some embodiments of the invention, is illustrated in Fig. 5 A. An apparatus 500 may include a sensor 510 that includes an RF opaque member 502 and an RF transparent conduit 504 (i.e., dielectric conduit) located within RF opaque member 504. Sensor 510 may further include a detector (not shown) such as detector 120. Apparatus 500 may include two RF obstructing members 522 each located at one end of sensor 510. Sensor 510 may be connected to RF transparent members 522 via flanges 626. In some embodiments, the inner diameter of RF transparent conduit 504 and the inner diameter of RF transparent members 522 are substantially the same, to avoid influencing the flow of the flowing material to be investigated. Also shown in Fig. 5 are portions of pipe 624, in which the material flows, for example, an oil pipe in an oil well. In Fig. 5 apparatus 500 is shown to be connected to pipe 624 by flanges 628. In some embodiments, the connection between the pipe and the apparatus may be by Grayloc™/DF interface connectors.

[00147] In some embodiments, for example, in an embodiment schematically depicted in Fig. 5B, apparatus 500B may include a metallic attenuating conduit portion 522B, and further, a dielectric attenuating conduit portion 624B, also referred to herein as an RF transparent member. Metallic attenuating conduit portion 522B may be attached to cavity 502, for example, with flange 626B. At its other end, metallic attenuating conduit portion 522B may be attached to dielectric attenuating conduit portion 624B, for example, with flange 628B. In some embodiments, the inner diameter of metallic attenuating conduit portion 522B and the inner diameter of dielectric attenuating conduit portion 624 are substantially the same, to avoid influencing the flow of the material to be investigated, and so may be the inner diameters of dielectric conduit 504 and attenuating conduit portion 522B. Accordingly, in some embodiments, the flow of material through conduit 504 and conduit portions 522 and 624 is smooth. Metallic attenuating conduit portion 522B may facilitate the decay of RF signals having frequencies below the opening cutoff frequency. While these frequencies decay when going out of RF opaque member 502 with or without metallic attenuating conduit portion 522B, they decay more rapidly with portion 522B in place, and thus, the RF transparent member 624B should deal with a narrower range of frequencies. In addition, it is expected that at least in some cases the sensor may show improved sensitivity with the metallic attenuating portion than without it, because more modes may be excitable in RF cavity 502 with the metallic attenuating portion than without it. Sensor 500B may replace a portion of the pipe (not shown in Fig. 5B) in which the material to be investigated flows.

[00148] Fig. 6 is an exemplary architecture within which an apparatus for determining a value of a property of a flowing material may be used, according to some embodiments of the present disclosure. In the example, the apparatus for determining the value of the property of the flowing material is a multi-phase flow meter working at an oil field. The multi-phase flow meter 800 is connected to a server 802 by network 850. Server 802 may be internal to network 850 (as illustrated), or external to network 850. In some embodiments, the network 850 is a cellular network. In other embodiments, the network 850 is a wireless local area network (WLAN), a global area network (GAN), local area network (LAN), wide area network (WAN), metropolitan area network (MAN), global system for mobile (GSM) network, code division multiple access network (CDMA), public switched telephone network (PSTN), packet switched network, mobile network, Bluetooth compatible network, near field communication (NFC), a hard wired network, a wireless network, a landline network, Zigbee, or a Wi-Fi network. Of course, it is understood that any network known by one of ordinary skill in the art may be employed.

[00149] The server 802 may be accessed through network 850 by, for example, SCADA (supervisory control and data acquisition) 804, analysts and operators 806, and field control 808.

[00150] SCADA 804 may be, for example, the data acquisition and control system of an oil well, to which multiphase flow meter (MPFM) 800 may send through network 850 some of the data it acquired, optionally, in real time. In some embodiments, communication between MPFM 800 and SCADA 804, as well as between any other two of SCADA 804, Analyst 806, Field Control 808 and MPFM 800, goes through the server. Communication to and from the server may be through network 850. In some embodiments, network 850 may include server 802. The data sent to the SCADA may include, for example, flow rate data, data relating to composition of the flowing material, etc. The SCADA may accordingly control, optionally through network 850, field control 808. In some embodiments, MPFM 800 may send instructions to field control 808 via network 850, without involving the SCADA in the process. The field control may be operable to control, for example oil pumping from the well, routing pumping products in the oil fields, etc. For example, if MPFM 800 finds out that the water content in the material is above a threshold, MPFM 800 may instruct intermitting the pumping, for example, for a predetermined period, to allow the water to settle. This may be done via the SCADA or directly via network 850.

[00151] Server 802 may receive from MPFM 800 on-line data on properties of the materials flowing through MPFM 800. In some embodiments, there may be several MPFM 800 units (e.g., if a field includes more than one well), and server 802 may receive data from all of them. In some embodiments, server 802 may receive samples of raw data, e.g., of measured s parameters at the different frequencies. Such data may be used for further analysis and study. Raw data not sent to server 802 may be stored on MPFM 800 for a short while, and then deleted to free space for new data coming in in real time. Sending all the raw data to the server may provide the possibility of further control and analysis, but may be omitted, for example, if communication lines are not available or too expensive to carry all that data.

[00152] Analyst/Operator 806 may provide data to the SCADA and/or to MPFM 800. For example, Analyst/Operator 806 may determine the threshold of water content mentioned above. In some embodiments, analyst/operator 806 may receive data samples from MPFM 800 (e.g., via server 802), to allow further analysis of the field production, for example, to estimate the overall production of the field, how the production is distributed over time, different productivities of different wells in the field, etc.

[00153] Each of SCADA 804, analysts and operators 806, and field control 808 can include stationary computer, a mobile computer, a personal computer (PC), a laptop computer, a tablet computer, a wireless smart phone, a personal digital assistant (PDA), a control system, or any other machine capable of executing a set of instructions (sequential or otherwise) that specify actions to be taken by that machine.

[00154] The server 802 may be connected to a database or other storage and/or memory devices with which data can be stored for later retrieval. The server 802, database, and or other components of the systems with which the system interacts may be implemented in a cloud-based environment. For example, the cloud-based environment may include a network of servers and web servers that provide processing and storage resources.

[00155] In this regard, the aforementioned components may possess the necessary hardware and software communications facilities necessary for bidirectional communications between the various components discussed. In this fashion, data measured and observed via the multi-phase flow meter 800 or any of its components can be transmitted in real-time to the server 802 via a cellular communications module or other wireless communications module, or any combination of hardware and/or software requirements known to one of ordinary skill in the art to facilitate the transmission and reception of data. Thus, the multi-phase flow meter 800 can transmit measured and observed data to the server 802, and/or can transmit an audio and/or visual alarm signal indicative of a foreign substance in conduit 104 (see Fig. 1A), e.g., deposits of wax on conduit walls,. The specific alarm signal to be sent can be dependent upon the particular foreign substance detected. For example, upon detection of a foreign substance, a lookup in a table or a query in a database, for example, could be performed to determine which foreign substance is associated with what alarm signal. In this regard, operators of the system can decide what substances are associated with what alarm signals, and store these preferences using an appropriate interface, for example via customers 804, operators 806 and/or field control 808. Alarm signals can also be sent for other conditions as high flow rate (e.g., higher than a predetermined high flow threshold), low flow rate (e.g., lower than a predetermined low flow threshold), and conditions associated with pressure differential, temperature, etc. For example, an alarm signal can be transmitted if a low flow rate is detected, which could be the result of an obstruction in the multi-phase flow meter, an obstruction elsewhere in the well or supply lines. Additionally, a high flow rate alarm signal can be provided to warn of a potential lack of capacity situation. Similarly, alarm signals associated with pressure differential can warn of potentially undesirable situations before becoming critical. The alarm signals can also be specific to the type of condition observed as discussed, i.e., high flow rate, low flow rate, etc.

[00156] Additionally or alternatively, field personnel and/or customers can transmit any operational instructions to the multi-phase flow meter 800 via software or Internet applications, for example. For example, field personnel can transmit instructions to the multi-phase flow meter 800 that instruct excitation to be applied through different feeds and different frequencies, in order to obtain the desired modes of excitation. Of course, other instructions can be sent as would be known by one of ordinary skill in the art.

[00157] The customers 804 are able to view the data from the server by an appropriate interface or portal accessible from suitable devices, as appreciated by one of skill in the art, associated with the customers.

[00158] An algorithm may be employed to support the identification of flow speeds and/or compositions of the flowing material. In some embodiments, the algorithm is a Python™ based program. The algorithm includes an estimation module, as will be discussed below.

[00159] In order to estimate the property of the material, e.g., the flow rate QL of a liquid through a sensor or a flow rate of gas through the sensor QA, the RF feeds in the sensor may provide samples of the scattering parameters Su, measuring the reflection coefficient to feed i when voltage is applied to the same feed i. In some embodiments, the RF feeds may also provide samples of the scattering parameters Sy measuring the transmission coefficient to feed i, when voltage is applied at feed j. An S parameter at frequency w is denoted by Sij(w) where i and j may be the same, to provide reflection coefficients, or different, to provide transmission coefficients. In some embodiments, wide band signatures may be analyzed to provide properties of the flowing material, such as flow rate and composition. In some embodiments, time variation may be used to provide the material properties. In some embodiments, both time variation and broad band signatures may be used.

[00160] The wide-band signature RF measurement may be used to find both composition of the material and flow rate of the material. The time variation measurement may also be used to determine composition and/or flow rate of the material.

[00161] With respect to wide-band signature measurement, N evenly spaced frequencies in the range [L;H], where [L; H] is wide and N is large may be used. Exemplary values may be N = 104, L= 1.0 GHz, and H = 6.5 GHz. For such a set of frequencies, W, and for a set of feeds P = { 1 ;2; ... ; K} , a wide-band signature x may be defined by:

[00162] x = {Si_j (w) I w £ W; i, j £ P)

[00163] A wide-band signature is a complex vector of size | W | | P | 2. In some embodiments, the dimensionality of the input space X may be reduced using supervised on unsupervised learning to obtain a reduced input space Z.

[00164] Given X (or Z) and the associated values of the properties (e.g., the flow rates and/or the compositions), Support Vector Regression may be used to find suitable mapping between the input space and the properties.

[00165] Machine learning techniques (for example, support vector regression) may be used to generate an estimator configured to estimate material properties based on the input vectors. For example, the input vectors, measured with materials of known properties, may be stored in a database in association with the corresponding material properties. This database may be used to generate the estimator. To use the estimator, spectra may be measured from materials having unknown properties (e.g., S parameters of the cavity when a material of unknown composition flows in the cavity at unknown flow rate). The estimator may then operate on these spectra (optionally, on these spectra in reduced form) to estimate the properties of the materials. In one embodiment (referred to herein as time variation embodiment), the input for the machine learning techniques and to the estimators they generate may include the degree by which the measured S parameter values vary over time. In such embodiments, the number of frequencies (or, more generally, excitation setups) used may be limited by the number of measurements that may be taken during a single time period. The single time period may be short enough so that the distance that the material flows within the single time period is small in comparison to the distance between the feeds along the material flow path.

[00166] Time-variation measures may use a smaller set of frequencies F, (e.g., | F | = 100), where each frequency is sampled several times along a given time interval T. Thus, dSi_j(w)/dt is evaluated for every frequency w, so that the dynamics of Sij can be correlated with flow rate.

[00167] Fig. 7 is an illustrative block diagram of a general computer system 900, on which a method for determining a value of a property of a material according to some embodiments of the present disclosure can be implemented. The computer system 900 can include a set of instructions that can be executed to cause the computer system 900 to perform any one or more of the methods or computer based functions disclosed herein. The computer system 900 may operate as a standalone device or may be connected, for example, using a network 901, to other computer systems or peripheral devices.

[00168] The computer system 900 can also be implemented as or incorporated into various devices, such as a stationary computer, a mobile computer, a personal computer (PC), a laptop computer, a tablet computer, a wireless smart phone, a personal digital assistant (PDA), a control system, or any other machine capable of executing a set of instructions (sequential or otherwise) that specify actions to be taken by that machine. The computer system 900 can be incorporated as or in a particular device that in turn is in an integrated system that includes additional devices. In a particular embodiment, the computer system 900 can be implemented using electronic devices that provide voice, video or data communication. Further, while a single computer system 900 is illustrated, the term "system" shall also be taken to include any collection of systems or sub-systems that individually or jointly execute a set, or multiple sets, of instructions to perform one or more computer functions.

[00169] As illustrated in Fig. 7, the computer system 900 includes a processor 910. A processor for a computer system 900 is tangible and non-transitory. As used herein, the term "non-transitory" is to be interpreted not as an eternal characteristic of a state, but as a characteristic of a state that will last for a period of time. The term "non-transitory" specifically disavows fleeting characteristics such as characteristics of a particular carrier wave or signal or other forms that exist only transitorily in any place at any time. A processor is an article of manufacture and/or a machine component. A processor for a computer system 900 is configured to execute software instructions in order to perform functions as described in the various embodiments herein. A processor for a computer system 900 may be a general purpose processor or may be part of an application specific integrated circuit (ASIC). A processor for a computer system 900 may also be a microprocessor, a microcomputer, a processor chip, a controller, a microcontroller, a digital signal processor (DSP), a state machine, or a programmable logic device. A processor for a computer system 900 may also be a logical circuit, including a programmable gate array (PGA) such as a field programmable gate array (FPGA), or another type of circuit that includes discrete gate and/or transistor logic. A processor for a computer system 900 may be a central processing unit (CPU), a graphics processing unit (GPU), or both. Additionally, any processor described herein may include multiple processors, parallel processors, or both. Multiple processors may be included in, or coupled to, a single device or multiple devices.

[00170] Moreover, the computer system 900 may include a main memory 920 and a static memory 930 that can communicate with each other via a bus 908. Memories described herein are tangible storage mediums that can store data and executable instructions, and are non-transitory during the time instructions are stored therein. A memory described herein is an article of manufacture and/or machine component. Memories described herein may include computer-readable mediums from which data and executable instructions can be read by a computer. Memories as described herein may be random access memory (RAM), read only memory (ROM), flash memory, electrically programmable read only memory (EPROM), electrically erasable programmable readonly memory (EEPROM), registers, a hard disk, a removable disk, tape, compact disk read only memory (CD-ROM), digital versatile disk (DVD), floppy disk, blu-ray disk, or any other form of storage medium known in the art. Memories may be volatile or nonvolatile, secure and/or encrypted, unsecure and/or unencrypted.

[00171] As shown, the computer system 900 may further include a display unit (e.g., video display unit 950), such as a liquid crystal display (LCD), an organic light emitting diode (OLED), a flat panel display, a solid state display, or a cathode ray tube (CRT). Additionally, the computer system 900 may include an input device 960, such as a keyboard/virtual keyboard or touch-sensitive input screen or speech input with speech recognition, and a cursor control device 970, such as a mouse or touch-sensitive input screen or pad. The computer system 900 can also include a disk drive unit 980, a signal generation device 990, such as a speaker or remote control, and a network interface device 940.

[00172] In a particular embodiment, as depicted in Fig. 7, the disk drive unit 980 may include a computer-readable medium 982 in which one or more sets of instructions 984, e.g. software, can be embedded. Sets of instructions 984 can be read from the computer- readable medium 982. Further, the instructions 984, when executed by a processor, can be used to perform one or more of the methods and processes as described herein. In a particular embodiment, the instructions 984 may reside completely, or at least partially, within the main memory 920, the static memory 930, and/or within the processor 910 during execution by the computer system 900.

[00173] In some embodiments, dedicated hardware implementations, such as application-specific integrated circuits (ASICs), programmable logic arrays and other hardware components, can be constructed to implement one or more of the methods described herein. One or more embodiments described herein may implement functions using two or more specific interconnected hardware modules or devices with related control and data signals that can be communicated between and through the modules. Accordingly, the present disclosure encompasses software, firmware, and hardware implementations. Everything in the present application should be interpreted as being implemented or implementable with software, hardware, or a combination of software and hardware. .

[00174] In accordance with various embodiments of the present disclosure, the methods described herein may be implemented using a hardware computer system that executes software programs. Further, in an exemplary, non-limited embodiment, implementations can include distributed processing, component/object distributed processing, and parallel processing. Virtual computer system processing can be constructed to implement one or more of the methods or functionality as described herein, and a processor described herein may be used to support a virtual processing environment. [00175] The present disclosure contemplates a computer-readable medium 982 that includes instructions 984 or receives and executes instructions 984 responsive to a propagated signal. Accordingly, the present disclosure enables a method and apparatus for determining a value of a property of a material that flows in a conduit inside a microwave cavity. For example, the processes contemplated herein include the determination of the water cut of crude oil, water liquid ratio (WLR), and/or gas volume fraction (GVF). The methods and apparatuses discussed herein may be employed, for example, in the oil and gas industries. As one example, in a well that produces oil and water, or gas and water, the individual flows of each of the substances can be measured. Additionally, the individual flows of oil, water, and gas may be measured. In another example, in Steam Assisted Gravity Drainage (SAGD) systems, embodiments of the present disclosure may be used for determining, for example, steam to oil ratio.

[00176] Exemplary applications may include processing crude and gas flows, monitoring and detecting fluid or gas loss, monitoring the flow of cooling liquids, measuring discharge. In the wet gas industry, metering and measuring may be performed at the well head prior to the mixing of multiple gas streams, or thereafter. In diaries, the apparatus and methods of the present disclosure may be used, for example, to obtain estimates of fat, sugar, and protein content of milk.

[00177] Another environment in which this is applicable to is underwater oil exploration and production. For example, in addition to monitoring the flow of crude and gas, the flow of foam or corrosion inhibitors or other chemicals injected into the stream may be metered and/or measured.

[00178] Additionally, another environment to which this is applicable is oil extraction such as hydraulic fracturing, commonly known as tracking. In addition to metering and measuring activities, identifying the composition of substances can also be performed. In this regard, chemicals used in hydraulic fracturing may be damaging to pipelines and storage vessels, and further, could lead to pollution during burning. To cope with such hazards, the method and apparatus described herein may be adapted to detect chemicals used during the hydraulic fracturing, including acids, salts, polyacrylamide, ethylene glycol, potassium carbonate, sodium carbonate, isopropanol, glutaraldehyde, lubricants, methanol, radionuclides, radioactive tracers, radioactive contaminants, etc. [00179] It is noted that the term Doppler signal refers to any variation over time of the measured system response function.

[00180] As used herein, the singular form "a", "an" and "the" include plural references unless the context clearly dictates otherwise. The use of the terms "at least one", "one or more", or the like in some places is not to be construed as an indication to the reference to singular only in other places where singular form is used.

[00181] As used herein the term "about" refers to + 10 %.

[00182] The terms "comprises", "comprising", "includes", "including", "having" and their conjugates mean "including but not limited to"; and encompass the terms "consisting of and "consisting essentially of .

[00183] It is appreciated that certain features of the invention, which are, for clarity, described in the context of separate embodiments, may also be provided in combination in a single embodiment. Conversely, various features of the invention, which are, for brevity, described in the context of a single embodiment, may also be provided separately or in any suitable sub-combination or as suitable in any other described embodiment of the invention. Certain features described in the context of various embodiments are not to be considered essential features of those embodiments, unless the embodiment is inoperative without those elements.

[00184] Although the invention has been described in conjunction with specific embodiments thereof, it is evident that many alternatives, modifications and variations will be apparent to those skilled in the art. Accordingly, it is intended to embrace all such alternatives, modifications, enhancements, and variations that fall within the spirit and broad scope of the appended claims. Thus, to the maximum extent allowed by law, the scope of the present disclosure is to be determined by the broadest permissible interpretation of the following claims and their equivalents, and shall not be restricted or limited by the foregoing detailed description.

[00185] The method and apparatus of the present disclosure, and aspects thereof, are capable of being distributed with a computer readable medium having instructions thereon. The term computer readable medium includes a single medium or multiple media, such as a centralized or distributed database, and/or associated caches and servers that store one or more sets of instructions. The term computer readable medium shall also include any medium that is capable of storing, encoding, or carrying a set of instructions for execution by a processor or that cause a computer system to perform any one or more of the methods or operations disclosed herein.

[00186] In a non-limiting exemplary embodiment, the computer readable medium can include a solid-state memory such as a memory card or other package that houses one or more non-volatile read-only memories. Further, the computer readable medium can be a random access memory or other volatile re-writable memory. Additionally, the computer readable medium can include a magneto-optical or optical medium, such as a disk or tapes or other storage device to capture carrier wave signals such as a signal communicated over a transmission medium. Accordingly, the disclosure is considered to include any computer readable medium or other equivalents and successor media, in which data or instructions may be stored.

[00187] While certain features of the invention have been illustrated and described herein, many modifications, substitutions, changes, and equivalents will now occur to those of ordinary skill in the art. It is, therefore, to be understood that the appended claims are intended to cover all such modifications and changes as fall within the true spirit of the invention.

Claims

CLAIMS [00188] What is claimed is:

1. An apparatus for determining a value of a property of a flowing material that flows through the apparatus, the apparatus comprising:

an RF cavity extending between a first end and a second end and being configured to allow the flowing material to flow through the RF cavity from the first end to the second end;

a detector configured to detect electrical responses of the RF cavity to incoming RF signals of various frequencies, and generate signals indicative of the detected electrical responses; and

an electromagnetically obstructing member positioned at at least one of the first end and the second end of the RF cavity without obstructing flow of material through said at least one of the first end and second end of the RF cavity.

2. An apparatus according to claim 1, wherein the electromagnetically obstructing member comprises an RF transparent member sized and positioned to form an electromagnetic opening between the RF cavity and a pipe feeding the RF cavity with the flowing material.

3. An apparatus according to claim 1 or 2, wherein the electromagnetically obstructing member comprises an RF absorbing member comprising a hollow conduit having RF absorbing wall.

4. An apparatus according to any one of claims 1 to 3, wherein changing the boundary conditions along a pipe feeding the RF cavity with the flowing material does not change readings of the detector by more than a predetermined degree.

5. An apparatus according to any one of claims 1 to 4, wherein the RF cavity has at the first end an opening with an opening-dimension defining an opening cutoff frequency, and wherein said various frequencies include at least one frequency above the opening cutoff frequency,

6. An apparatus according to claim 5, wherein the various frequencies span a frequency range, the highest frequency thereof is at least 3 times higher than the lowest frequency thereof.

7. An apparatus according to claim 6, wherein at least a quarter of said frequency range is above the opening cutoff frequency.

8. An apparatus according to any one of claims 1 to 7, comprising a sensor, the sensor comprising the RF cavity, the detector, and an RF transparent conduit located within the RF cavity, the RF transparent conduit being configured to direct the flowing material through the RF cavity.

9. An apparatus according to claim 8, wherein the RF transparent conduit has substantially the same dielectric constant as the flowing material.

10. An apparatus according to any one of claims 1 to 9, wherein the RF transparent conduit and the electromagnetically obstructing member are configured so that material flowing through the RF cavity continues flowing without obstruction through the RF transparent member or vice versa.

11. An apparatus according to any one of claims 1 to 9, comprising two

electromagnetically obstructing members, one at each end of the RF cavity.

12. An apparatus according to claim 11 , wherein the RF cavity and the

electromagnetically obstructing members are so configured, that material flowing through one electromagnetically obstructing member continues flowing without obstruction through the RF cavity, and from the RF cavity through the other electromagnetically obstructing member.

13. An apparatus according to any one of claims 8 to 12, wherein the sensor comprises a feed for feeding the RF cavity with RF radiation, and the feed comprises a radiating element ending outside the RF cavity.

14. An apparatus according to claim 13, comprising a source of RF radiation configured to supply RF radiation at the various frequencies to the RF cavity through the feed.

15. An apparatus according to claim 14, comprising a processor configured to determine the value of the property based on the signals generated by the detector.

16. An apparatus for determining a value of a property of a material flowing inside a pipe, the apparatus comprising:

a radio frequency (RF) resonator extending between a first end and a second end, each end having an opening to allow the material to go in and out the RF resonator, wherein said opening defines an opening cutoff frequency;

at least one feed configured to feed the resonator with RF radiation;

at least one source configured to supply to the feed RF energy at a frequency range, wherein at least 1/4 of the frequency range is above the opening cutoff frequency;

a detector, configured to detect parameters indicative of electrical response of the RF resonator to radio frequency (RF) radiation fed to the RF resonator through the at least one feed;

a processor, configured to determine the value of the property based on the parameters detected by the detector; and

an electromagnetically obstructing member, between the resonator and the pipe, electromagnetically isolating the resonator from the pipe without obstructing material flow from the pipe through the resonator.

17. An apparatus according to claim 16, wherein the electromagnetically obstructing member comprises an RF transparent member sized to form an open electromagnetic boundary.

18. An apparatus according to claim 16 or 17, wherein the electromagnetically obstructing member comprises an RF absorbing member sized to form an

electromagnetic obstruction at least at those of the various frequencies that are higher than the opening cutoff frequency.

19. An apparatus according to any one of claims 16 to 18, wherein in operation the electric field between the resonator and the RF obstructing member is larger by at least factor 100 than between the RF obstructing member and the pipe.

20. A method of determining a value of a property of a material that flows in a pipe, the method comprising: replacing a portion of the pipe by an apparatus according to any one of the preceding claims; and operating the apparatus to determine the property.