Flow sensors

Abstract

Disclosed are devices, systems, and techniques for providing improved flow measurement. In some embodiments, a flow sensor may be provided. The sensor may include a substrate having an upstream-oriented surfaces and a downstream-oriented surface. The substrate may be configured to generate an upstream stagnation region extending upstream from the upstream-oriented surface and a downstream stagnation region extending downstream from the downstream-oriented surface. At least one conductive wire may be disposed within the upstream stagnation region, the downstream stagnation region, or both. The wire(s) may be a distance d from the closest surface of the substrate, where d > 0, the at least one conductive wire being operably coupled to circuitry on the first substrate.

Description

[0001] FLOW SENSORS

[0002] TECHNICAL FIELD

[0003] The present application is drawn to flow sensors, such as volumetric or mass flow rate sensors, systems, and techniques.

[0004] BACKGROUND

[0005] This section is intended to introduce the reader to various aspects of art, which may be related to various aspects of the present invention that are described and / or claimed below. This discussion is believed to be helpful in providing the reader with background information to facilitate a beter understanding of the various aspects of the present invention. Accordingly, it should be understood that these statements are to be read in this light, and not as admissions of prior art.

[0006] Flow sensors are critical in modem day life. They are needed, for example, in industries ranging from oil and gas, water and wastewater, agriculture, paper and pulp, chemical, power generation, and food and beverage. Conventional sensor designs must make tradeoffs between accuracy, sensitivity, cost, and reliability .

[0007] BRIEF SUMMARY

[0008] Various deficiencies in the prior art are addressed below by the disclosed devices, systems, and techniques.

[0009] In various aspects, a flow sensor may be provided. The flow sensor may include a first substrate. The first substrate may have two opposing surfaces, such as a first surface and a second surface opposite the first surface. The first surface may be configured to generally face an upstream direction in a flow of a fluid, the second surface being configured to generally face a downstream direction in the flow of the fluid. The first substrate may be configured to generate an upstream stagnation region extending upstream from the first surface and a downstream stagnation region extending downstream from the second surface.

[0010] The flow sensor may include at least one conductive wire disposed within the upstream stagnation region, the downstream stagnation region, or both. The at least one conductive wire may be located a distance d from the first substrate, where d > 0.

[0011] The at least one conductive wire may be operably coupled to circuitry' on the first substrate. The circuitry may include only conductive leads. The circuitry may include various other components, such as a processor. In some embodiments, an I / O port may be coupled to the circuitry.

[0012] The at least one conductive wire may be disposed within at least one sensor subcomponent. The at least one sensor subcomponent may include a second substrate having opposing surfaces (e.g., a third surface and a fourth surface opposite the third surface). The third surface may face the first substrate. Each second substrate may have an opening extending from the third surface to the fourth surface. The at least one conductive wire may extend across the opening in a direction parallel to the third surface. The at least one conductive wire may include a plurality of conductive wires.

[0013] In some embodiments, a distance separating each wire of the plurality of conductive wires from an adjacent wire may be 0.1-25 times a width dimension of the wire. In some embodiments, a width dimension of each conductive wire may be 0.5 pm-40 pm, and the distance separating each conductive wire from an adjacent conductive wire may be 1 pm-60 pm.

[0014] Each conductive wire may have at least one dimension that is less than 1 pm. Each conductive wire may have at least one dimension that is less than 200 nm. A length-to-width aspect ratio of each conductive wire may be 1 - 500. Each conductive wire may have a rectangular cross-section. One or more of the at least one conductive wire may include a pure metal or a metal alloy. Each conductive wire may be composed of platinum. One or more of the at least one conductive wire may include an electrically conductive polymer. One or more of the at least one conductive wire may include a semiconductor material. One or more of the at least one conductive wire may include two or more materials. Each conductive wire may be composed of platinum and titanium. The at least one conductive wire may be coated with a non-conductive material. The non-conductive material can serve as a passivation layer. The non-conductive material may be a non-conductive polymer, such as parylene.

[0015] The sensor may be configured such that each conductive wire may have a temperature between 50°C and 500°C. The sensor may be configured such that each conductive wire may have a temperature that changes with flow rate of the fluid and is configured to be maintained more than 5°C warmer than a temperature of the fluid.

[0016] The at least one sensor subcomponent may include a Wheatstone bridge. The at least one sensor subcomponent may include at least one additional wire, beyond the at least one conductive wire. The additional wire may be configured to measure temperature. The at least one sensor subcomponent may include at least two conductor elements configured to contact the fluid. In some embodiments, the at least two conductor elements are configured to measure the resistivity of the fluid. In some embodiments, all sensor subcomponents may be disposed at fixed distance(s) dl > 0 in a direction normal to the first surface of the first substrate. In some embodiments, all sensor subcomponents may be disposed at fixed distance(s) d2 > 0 in a direction normal to the second surface of the first substrate. In some embodiments, at least one sensor subcomponent may be disposed at a fixed distance dl > 0 in a direction normal to the first surface of the first substrate, and at least one sensor subcomponent may be disposed at a fixed distance d2 > 0 in a direction normal to the second surface of the first substrate.

[0017] The sensor may include at least one opening extending from the first surface to the second surface of the first substrate. The first substrate may include a plurality of openings, each opening extending from the first surface to the second surface. The sensor may include at least one communications interface coupled to the circuitry.

[0018] In various aspects, a flow sensor system may be provided. The flow sensor system may include at least one housing through which a fluid may be configured to flow. The system may include a flow sensor as disclosed herein. The sensor may be operably coupled to the at least one housing, such that fluid is configured to flow around the first substrate or through an opening in the first substrate of the flow sensor. The at least one housing may include at least a first housing and a second housing. The first and second housing may be coupled together. The first housing may be operably coupled to an upstream surface of the flow sensor. The second housing may be operably coupled to a downstream surface of the flow sensor.

[0019] The system may include a first o-ring between the first housing and the flow sensor. The system may include a second o-ring between the second housing and the flow sensor. In some embodiments, at least a portion of the flow sensor may be disposed within the at least one housing, and at least a portion of the flow sensor may be disposed external to the at least one housing. In some embodiments, the flow sensor may be disposed within the at least one housing.

[0020] The system may include a measuring circuit operably coupled to the at least one conductive wire configured to measure at least one of a voltage or a current. The system may include a power circuit operably coupled to the at least one conductive wire configured to ensure each wire operates with an overheat ratio a of between 1.01 and 5. In some embodiments the power circuit is connected to the at least one conductive wire through a Wheatstone bridge.

[0021] The system may include at least one processor operably coupled to the measuring circuit. The at least one processor may be configured to, collectively, receive first information from the measuring circuit, the first information comprising a voltage and / or a current. The at least one processor may be configured to, collectively, transmit the first information or representations of the first information to one or more remote processors. The at least one processor may be configured to, collectively, calculate a mass and / or volumetric flow rate based on the first information. The mass and / or volumetric flow rate may be integrated over time to measure cumulative mass or volume past the substrate. The at least one processor may be configured to, collectively, transmit a rate of mass and / or volumetric flow and / or a cumulative mass or volume to one or more remote processors.

[0022] In various aspects, a method for determining cumulative flow of a fluid may be provided. The method may include allowing the fluid to flow around or through a substrate, where at least one conductive wire is disposed within a stagnation region of the substrate. The method may include passing a current through the at least one conductive wire such that it is heated up. The method may include measuring a voltage or current across the at least one conductive wire. The method may include determining a flow rate from the voltage or current.

[0023] The method may include determining a cumulative mass and / or volume of fluid through the at least one conductive wire by integrating the flow rate overtime. The method may include adjusting at least one valve based on the flow rate or cumulative mass and / or volume of fluid. The method may include determining a temperature within the fluid based on a current or voltage across at least one additional wire in the stagnation region. The method may include determining a conductivity or resistivity of the fluid based on a current or voltage across at least at least two conductor elements in contact with the fluid. The sensitivity of the at least one conductive wire may be controlled by reducing or increasing a size of the stagnation region. The more sensitive one wants the sensor to be to the flow rate, the smaller the stagnation region should be controlled to be. The size of the stagnation region may be controlled by adjusting an angle of the substrate relative to a direction of fluid flow past the substrate. The size of the stagnation region may be controlled by adjusting a location and / or size of an opening extending through the substrate. The size of the stagnation region may be controlled by a shape of the substrate. The size of the stagnation region may be controlled by the location and size of openings in the substrate. The size of the stagnation region may be controlled by the shape of a structure housing the substrate.

[0024] BRIEF DESCRIPTION OF FIGURES

[0025] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the present invention and, together with a general description of the invention given above, and the detailed description of the embodiments given below, serve to explain the principles of the present invention.

[0026] Figure 1 is an illustration of an embodiments of a flow sensor.

[0027] Figure 2A is an illustration of a cross-section of an embodiment of a sensor subcomponent.

[0028] Figure 2B is an illustration showing an embodiment of circuitry on a second substrate, including a conductive wire over an opening in the second substrate.

[0029] Figures 3 A and 3B are illustrations of embodiments of flow sensors.

[0030] Figures 4A-4F are illustration of cross-sections of embodiments of flow sensor devices.

[0031] Figure 5 is an illustration of an embodiment of a system.

[0032] Figures 6 and 7 are illustrations of cross-sections of embodiments of systems.

[0033] Figure 8 is an illustration of an embodiment of a system.

[0034] Figures 9A and 9B are illustrations of cross-sections of embodiments of housings.

[0035] Figure 10 is a block diagram of an embodiment of a system.

[0036] Figure 11 is a flowchart of an embodiment of a method.

[0037] Figure 12A and 12B are illustrations of cross-sections of embodiments, showing the impact on stagnation regions when a sensor in a first configuration (12A) is placed in a second configuration (12B).

[0038] Figure 13 is a graph showing an example of voltages measured by a sensor in real time.

[0039] Figure 14 is a graph showing an example of a conversion of the voltages to flow rates. The sensor signal shown is determined as - ([voltage] - [voltage at zero flow]).

[0040] Figure 15 is an illustration showing an embodiment of a system.

[0041] It should be understood that the appended drawings are not necessarily to scale, presenting a somewhat simplified representation of various features illustrative of the basic principles of the invention. The specific design features of the sequence of operations as disclosed herein, including, for example, specific dimensions, orientations, locations, and shapes of various illustrated components, will be determined in part by the particular intended application and use environment. Certain features of the illustrated embodiments have been enlarged or distorted relative to others to facilitate visualization and clear understanding. In particular, thin features may be thickened, for example, for clarity' or illustration.

[0042] DETAILED DESCRIPTION

[0043] The following description and drawings merely illustrate the principles of the invention. It will thus be appreciated that those skilled in the art will be able to devise various arrangements that, although not explicitly described or shown herein, embody the principles of the invention and are included within its scope. Furthermore, all examples recited herein are principally intended expressly to be only for illustrative purposes to aid the reader in understanding the principles of the invention and the concepts contributed by the inventor(s) to furthering the art and are to be construed as being without limitation to such specifically recited examples and conditions. Additionally, the term, "or," as used herein, refers to a nonexclusive or, unless otherwise indicated (e.g, “or else” or “or in the alternative”). Also, the various embodiments described herein are not necessarily mutually exclusive, as some embodiments can be combined with one or more other embodiments to form new embodiments.

[0044] The numerous innovative teachings of the present application will be described with particular reference to the presently preferred exemplary embodiments. However, it should be understood that this class of embodiments provides only a few examples of the many advantageous uses of the innovative teachings herein. In general, statements made in the specification of the present application do not necessarily limit any of the various claimed inventions. Moreover, some statements may apply to some inventive features but not to others. Those skilled in the art and informed by the teachings herein will realize that the invention is also applicable to various other technical areas or embodiments.

[0045] As used herein, the term “downstream” refers to a position within a conduit or flow path, relative to a surface, component, etc., where a fluid has moved through, around, or otherwise past the surface, component, etc. in the conduit or flow path Said differently, “downstream [from a surface, component, etc.]” refers to a point in a conduit or fluid path where the point is between the surface, component, etc. and the end of the conduit or fluid path.

[0046] As used herein, the term “downstream direction” refers to any direction in a conduit or fluid path wherein fluid in that direction would be considered downstream from a given surface, component, etc. In some embodiments, this may be a direction normal to the surface. In some embodiments, this may be a direction that is no more than 15 degrees from normal to the surface. In some embodiments, this may be a direction that is no more than 30 degrees from normal to the surface. In some embodiments, this may be a direction that is no more than 45 degrees from normal to the surface. In some embodiments, this may be a direction that is no more than 60 degrees from normal to the surface. In some embodiments, this may be a direction that is no more than 75 degrees from normal to the surface. In some embodiments, this may be a direction that is less than 90 degrees from normal to the surface. As used herein, the term “overheat ratio” refers to the ratio of wire temperature over fluid temperature, in Kelvin.

[0047] As used herein, the term “processor” refers to at least the hardware for executing instructions defined by a particular instruction set that may be stored in a computer memory' (e.g., ROM or oilier computer memory). This includes, but is not limited to, any integrated circuit or any other electronic device (or collection of electronic devices) capable of performing an operation on at least one instruction, including, without limitation, a microprocessor (pP), a microcontroller (pC), a Digital Signal Processor (DSP), or any combination thereof.

[0048] As used herein, the term “stagnation region” refers to a region with decelerated flow relative to the velocity of the bulk flow the sensor is designed to measure. These regions are formed adjacent to a surface and may extend some distance upstream (or downstream) from the surface. In some embodiments, this may be a region where the velocity is no more than 10% of the velocity of the bulk flow the sensor is designed to measure. In some embodiments, this may be a region where the velocity is no more than 25% of the velocity of the bulk flow the sensor is no more to measure. In some embodiments, this may be a region where the velocity is less than 50% of the velocity of the bulk flow the sensor is designed to measure. In some embodiments, this may be a region where the velocity is no more than 70% of the velocity of the bulk flow the sensor is designed to measure. In some embodiments, this may be a region where the velocity is no more than 90% of the velocity of the bulk flow the sensor is designed to measure.

[0049] As used herein, the term “upstream” refers to a position within a conduit or flow path, relative to the surface, component, etc., where a fluid has not yet moved through, around, or otherwise past the surface, component, etc. in the conduit or flow path. Said differently, “upstream [from a surface, component, etc.]” refers to a point in a conduit or fluid path where the point is between the surface, component, etc. and the start of the conduit or fluid path.

[0050] As used herein the term “upstream direction” refers to any direction in a conduit or fluid path wherein fluid in that direction would be considered upstream from a given surface, component, etc. In some embodiments, this may be a direction normal to the surface. In some embodiments, this may be a direction that is no more than 15 degrees from normal to the surface. In some embodiments, this may be a direction that is no more than 30 degrees from normal to the surface. In some embodiments, this may be a direction that is no more than 45 degrees from normal to the surface. In some embodiments, this may be a direction that is no more than 60 degrees from normal to the surface. In some embodiments, this may be a direction that is no more than 75 degrees from normal to the surface. In some embodiments, this may be a direction that is less than 90 degrees from normal to the surface.

[0051] In various aspects, a flow sensor may be provided. Referring to FIG. 1, a flow sensor 100 may include a first substrate 110. The first substrate may be a rigid substrate. The first substrate may include an insulating material. The first substrate may include a dielectric material. In some embodiments, the first substrate includes a polymeric material. In some embodiments, the first substrate is a circuit board, and may include, e.g., fiberglass. In some embodiments the substrate may include a ceramic material.

[0052] The first substrate may have two opposing surfaces, such as a first surface 111 and a second surface 112 opposite the first surface. In some embodiments, the first and second surface may be separated by one or more sides 113.

[0053] Referring briefly to FIG. 4A, the first surface 111 may be configured to generally face an upstream direction 401 in a flow 420, 421 of a fluid, the second surface 112 being configured to generally face a downstream direction 402 in the flow of the fluid. The first substrate may be configured to generate an upstream stagnation region 431 extending upstream from the first surface 111 and a downstream stagnation region 432 extending downstream from the second surface 112. The flow sensor may include at least one conductive wire 150 disposed within the upstream stagnation region, the downstream stagnation region, or both. The at least one conductive wire may be located a distance 135 (d) from the first substrate, where d > 0.

[0054] Referring again to FIG. 1, the at least one conductive wire 150 may be operably coupled to circuitry 140 on the first substrate. In some embodiments, the circuitry 140 may include only conductive leads 141. Referring briefly to FIG. 3A, in some embodiments, the circuitry 140 may include various other components, such a processor 321. In some embodiments, a communications interface or I / O port 325 may be coupled to the circuitry.

[0055] Referring to FIG. 2A, the at least one conductive wire 150 may be disposed within at least one sensor subcomponent 130. Referring to FIG. 2B, the at least one sensor subcomponent may include a Wheatstone bridge, where the at least one conductive wire represents one element in the Wheatstone bridge.

[0056] The sensor subcomponent may be, e.g., no more than 20 mm wide (e.g., left-to-right as seen in FIG 2A), no more than 10 mm wide, no more than 5 mm wide. The sensor subcomponent may be, e.g. , no more than 20 mm high (e.g. , top-to-bottom as seen in FIG. 2A), no more than 10 nun high, or no more than 5 nun high. The sensor subcomponent may be, e.g., no more than 10 mm deep (e.g., direction parallel to central axis of opening 134 as seen in FIG. 2 A), no more than 5 mm deep, no more than 3 mm deep, or no more than 1mm deep. The at least one sensor subcomponent 130 may include a second substrate 131 having opposing surfaces (e.g, a third surface 132 and a fourth surface 133 opposite the third surface). Each second substrate may have an opening 134 extending from the third surface to the fourth surface. The shape of the opening may take many different forms. The opening may be e.g. rectangular in shape, oval in shape, circular in shape or conical in shape. The opening may be e.g. no more than 5 mm wide (e.g., left-to-right as seen in FIG. 2A), no more than 2 mm wide, or no more than 1mm wide. The at least one conductive wire 150 may extend across the opening in a direction parallel to the third surface. The at least one conductive wire may include a plurality of conductive wires, including, e.g., a first wire 200 and a second wire 201.

[0057] In some embodiments, the third surface may be configured to face the first substrate. In some embodiments, the third surface may be configured to face away from the first substrate. The third surface may be parallel to the first surface.

[0058] In some embodiments, a distance 205 separating each wire of the plurality of conductive wires from an adj acent wire may be 0.1 -25 times a width dimension 206 of the wire (e.g. in FIG. 2A a direction parallel to the central axis of opening 134). In some embodiments, a width dimension of each conductive wire may be 0.5 pm-40 pm, and the distance separating each conductive wires from an adjacent conductive wire may be 0.5 pm-60 pm. Each conductive wire may have at least one dimension that is less than 1 pm. Each conductive wire may have at least one dimension that is less than 0.3pm.

[0059] In some embodiments, each conductive wire is configured such that the deflection at long its length in the direction of fluid flow that is zero at velocities up to a maximum predetermined operating velocity. In some embodiments, each conductive wire may be configured to have a maximum deflection of less than 0.01% of its length at velocities up to a maximum predetermined operating velocity. For various applications, the maximum predetermined operating velocities may differ greatly. In some applications, the maximum expected velocity may be 1 m / s. In some applications, the maximum expected velocity may be 5 m / s. In some applications, the maximum expected velocity may be 10 m / s. In some applications, the maximum expected velocity may be 20 m / s. In some applications, the maximum expected velocity may be 50 m / s. In some applications, the maximum expected velocity may be 100 m / s. In some applications, the maximum expected velocity may be 200 m / s. In some applications, the maximum expected velocity may be 500 m / s. In some applications, the maximum expected velocity may be 1000 m / s. In some applications, the maximum expected velocity may be 2000 m / s. The sensor may be configured for use with a predetermined range of fluids. The expected fluid to be measured may be a gas or a liquid. In some embodiments, the fluid may include water. In some embodiments, the fluid may be a solvent, hydrocarbon, or alcohol. In some embodiments, the fluid may include a COX, NOX, and / or SOXmaterial. In some embodiments, the fluid may have an absolute viscosity no more than 0.1 cP. In some embodiments, the fluid may have an absolute viscosity no more than 1 cP. In some embodiments, the fluid may have an absolute viscosity no more than 10 cP. In some embodiments, the fluid may have an absolute viscosity no more than 100 cP. In some embodiments, the fluid may have an absolute viscosity no more than 1000 cP. In some embodiments, the fluid may have an absolute viscosity no more than 1,000 cP. In some embodiments, the fluid may have an absolute viscosity no more than 10,000 cP. In some embodiments, the fluid may have an absolute viscosity no more than 100,000 cP. In some embodiments, the fluid may have an absolute viscosity no more than 1,000,000 cP.

[0060] Each conductive wire may have a length-to-width aspect ratio that may be 1 - 500. In some embodiments the length-to-width aspect ratio of each conductive wire may be 5-500 Each conductive wire may have a rectangular cross-section.

[0061] One or more of the at least one conductive wire may include a pure metal or a metal alloy. Each conductive wire may be composed of platinum. One or more of the at least one conductive wire may include an electrically conductive polymer. One or more of the at least one conductive wire may include a semiconductor material. One or more of the at least one conductive wire may include two or more materials. Each conductive wire may be composed of platinum and titanium. The at least one conductive wire may be coated with a non- conductive material. The non-conductive material may be a non-conductive polymer, such as parylene.

[0062] The sensor may be configured such that each conductive wire may have a temperature between 50°C and 500°C. The sensor may be configured such that each conductive wire may have a temperature that changes with flow rate of the fluid and may be configured to be maintained more than 5°C warmer than a temperature of the fluid.

[0063] Referring to FIG. 2A, in some embodiments, the sensor subsystem may include one or more conductive pads 202 electrically coupled to each wire or element. In some embodiments, each wire or element is electrically coupled to other circuitry on the subsystem, which may include a Wheatstone bridge.

[0064] As seen in FIG. 2A, the at least one sensor subcomponent may include at least one additional wire 203, in addition to the at least one conductive wire. The additional wire may be configured to measure temperature. That is, by using a wire sensitive to temperature changes, a temperature of a fluid can be determined based on a change in an electrical property, such as voltage, current, or resistance.

[0065] An embodiment of circuitry on the sensor subcomponent can be seen in FIG. 2B. As seen, the circuitry 250 may include a Wheatstone bridge, where each resistor element 260 consists of a series of wires 270, 271. One of these resistors elements sits over opening 134. Here, this is shown as at least one conductive wire 150. In some embodiments, a conductive pad 202 may be disposed between two adjacent resistors elements. As will be understood, the circuitry may include other electrical components, including, e.g., additional wires, electrodes, etc., as disclosed herein.

[0066] The at least one sensor subcomponent may include at least two conductor elements 204 configured to contact the fluid but not each other. The two conductor elements may be used to determine, e.g., a conductivity or resistivity of the fluid. In some embodiments the resistivity of the water is used to determine the level of total dissolved solids (TDS). In some embodiments, all wires or elements are on the same surface .g., third surface 132). In some embodiments, at least one of the wires or elements are on a different surface from at least one other wire or element. For example, in some embodiments, a plurality of conductive wires are on the third surface, while the additional wire for temperature and / or the two conductor elements are on the fourth surface.

[0067] Referring briefly to FIG. 4A, in some embodiments, all sensor subcomponents may be disposed at fixed distance(s) dl > 0 in a direction normal to the first surface of the first substrate (e.g., in an upstream direction).

[0068] Referring briefly to FIG. 4B, in some embodiments, at least one sensor subcomponent may be disposed at a fixed distance dl > 0 in a direction normal to the first surface of the first substrate (e.g., in an upstream direction), and at least one sensor subcomponent may be disposed at a fixed distance d2 > 0 in a direction normal to the second surface of the first substrate (e.g, in a downstream direction).

[0069] Referring briefly to FIG. 4C, In some embodiments, all sensor subcomponents may be disposed at fixed distance(s) d2' > 0 in a direction normal to the second surface of the first substrate (e.g., in a downstream direction).

[0070] Referring again to FIG. 1, the sensor may include at least one opening 120 extending from the first surface 111 to the second surface 112 of the first substrate. The first substrate may include a plurality of openings, each opening extending from the first surface to the second surface. In FIG. 1, the sensor is shown as only including conductive leads. Referring to FIG. 3A, in some embodiments, the sensor may include other circuitry components on the first substrate. In some embodiments, a processor 321 may be included. In some embodiments, a power circuit 322 may be included, for providing the necessary power to the various wires or elements. In some embodiments, a measuring circuit 323 may be included, which may include a Wheatstone bridge, for measuring electrical characteristics of the various wires or elements. In some embodiments an amplifier may be included on the first substrate.

[0071] Referring to FIG. 3B, in some embodiments, the majority of the circuitry 320 is on a separate substrate 310. Circuitry' 320 is electrically coupled to the circuitry on the sensor (here, conductive leads 141). This may include having one or more wires 330 or cables electrically connected to the conductive leads 141 via, e.g, one or more conductive pads 142.

[0072] As shown in FIG. 3B, multiple sensor subsystems may be present on a sensor, and the sensor does not require openings through the first substrate. When no openings are present, the first substrate may be configured to cause the fluid to flow around the first substrate.

[0073] Referring to FIG. 4A, a sensor can be seen where fluid has flow paths 420, 421 through openings 120 in the substrate, creating upstream stagnation region 431 and downstream stagnation region 432. As seen, the sensor subsystem 130 is disposed within the upstream stagnation region, and is coupled to the first substrate via one or more layers 410. The one or more layers may include any appropriate material for attaching the sensor subsystem to the first substrate. This may include, e.g, an adhesive, a magnet, solder, gold, etc. As shown in FIG. 4A, the one or more conductive wires 150 may be disposed between the first substrate 110 and the second substrate 131.

[0074] Referring to FIG. 4B, it is seen that separate sensor subsystems may be coupled to the upstream surface (here, first surface 111) and downstream surface (here, second surface 112) of a sensor, in the appropriate stagnation regions. Referring to FIG. 4C, it is seen that a sensor subsy stem may be disposed only within the downstream stagnation region. Referring to FIG. 4D, it is seen that a sensor subsystem may be disposed within a stagnation region, but where the conductive wires 150 are disposed on the fourth surface 133 facing away from the first substrate 110. In this configuration, in various embodiments, there may be wire bonds going from the wire side of the sensor subcomponent to the first substrate.

[0075] Referring to FIG. 4E, a system similar to that of FIG. 4A is seen, but where there are no openings in the first substate. In this case, the flow paths 420, 421 are configured to pass around the first substrate (e.g, past edges 113), and still generate, e.g., an upstream and / or downstream stagnation region. It will be understood that the shape of the substrate may alter the shape and size of the stagnation region. Typically, the more aerodynamic the shape, the smaller the region, and the less aerodynamic the shape, the larger the region.

[0076] The sensitivity of the disclosed sensors to flow rate changes may be related to the shortest distance 440 between the at least one conductive wire and an edge 433 of the stagnation region 431. The smaller the distance 440, the more sensitive the sensor may be. Conversely, the larger the distance 440, the less sensitive the sensor may be.

[0077] Referring to FIG. 4F, one or more openings 120 may be adjusted. For example, one or more openings may have a shutter 460 configured to have an adjustable position, such as via an actuator 461, wherein none, some, or all of the opening may be blocked by the shutter. In some embodiments, this is a diaphragm or leaf shutter. In some embodiments, the shutter may be configured to be slidably positioned along a single axis parallel to the first surface (for example, as a single rigid layer that slides in or out of position). In some embodiments, the shutter may be configured to be passively adjusted such that the higher the flow rate the more less sensitive the sensor is, increasing the total range of the sensor. This may be achieved using an elastic material reacting to the forces in the flow.

[0078] In various aspects, a flow sensor system may be provided. Refernng to FIG. 5, a flow sensor system 500 may include at least one housing 510, 520 through which a fluid may be configured to flow. In FIG. 5, the fluid is configured such that, upstream of the sensor, the fluid flows 530 into an inlet of a first housing 510, through openings 120 in the sensor 100, into the second housing 520, and then flow 540 out of an outlet.

[0079] The system may include a flow sensor 100 as disclosed herein.

[0080] The sensor may be operably coupled to the at least one housing, such that fluid may be configured to flow around the sensor or through an opening in the first substrate of the flow sensor, such as the arrangements seen in FIGS. 4A-4F.

[0081] The at least one housing may include at least a first housing 510 and a second housing 520. In some embodiments, the first and second housing may be coupled together. In some embodiments the coupling is permanent.

[0082] Referring to FIG. 6, in some embodiments, the first housing 510 may be operably coupled to an upstream surface 111 of the flow sensor. The second housing 520 may be operably coupled to a downstream surface 112 of the flow sensor.

[0083] The system may include a first o-ring 620 between the first housing and the flow sensor. The system may include a second o-ring 621 between the second housing and the flow sensor. The o-rings may be compressible. The o-rings may be elastomeric. In some embodiments the o-ring is integrated into the housing. In some embodiments the o-rings are replaced by at least one gasket.

[0084] In some embodiments, the housing may be a tube, pipe, vessel, etc. for the fluid. Referring to FIG. 7, in some embodiments, the housing 710 may have an external surface 711 and an internal surface 712 defining a channel though which fluid flows 730. In some embodiments, at least a portion 720 of the flow sensor may be disposed within the at least one housing, and at least a portion 721 of the flow sensor may be disposed external to the at least one housing.

[0085] Referring to FIG. 8, in some embodiments, the flow sensor may be disposed entirely within the at least one housing.

[0086] Referring to FIG. 9A, the first housing 510 and second housing 520 may be coupled together, such as being hingedly coupled together via a hinge joint 910. Referring to FIG. 9B, a first housing 510 may have an upstream portion 920, and a downstream portion 921. The two portions may be coupled together via an intermediate flexible joint 922. The housing may have an open configuration and a closed configuration. When in the closed configuration, the housing may include a gap 923 configured to allow a sensor as disclosed herein to be disposed within the gap and coupled to both the upstream and downstream portions. In some embodiments the housings are w elded together.

[0087] Referring to FIG. 3B, the system may include a measuring circuit 323 operably coupled to the at least one conductive wire 150, the measuring circuit configured to measure at least one of a voltage or a current across the at least one conductive wire.

[0088] The system may include a power circuit 322 operably coupled to the at least one conductive wire configured to ensure each wire operates with an overheat ratio a of between 1.01 and 5.

[0089] The system may include at least one processor 321, 341 operably coupled to the measuring circuit. In some embodiments, a processor 321 may be on a separate substrate 310 from the sensor. In some embodiments, a processor 341 may be, e.g., a remote CPU or GPU, such as on a remote computer 340, server, tablet, or smartphone. Each processor may be operably coupled to a non-transitory computer-readable storage device, such as storage device 342. In some embodiments the processor communicates wirelessly with the sensor.

[0090] The at least one processor may be configured to, collectively, receive first information from the measuring circuit, the first information comprising a voltage and / or a current. Referring to FIG. 13, an example of real-time voltage information received from a sensor can be seen. In some embodiments, every datapoint is sent to the processor. The at least one processor may be configured to, collectively, transmit the first information or representations of the first information to one or more remote processors (such as from processor 321 to remote processor 341) .

[0091] The at least one processor may be configured to, collectively, calculate a mass and / or volumetric flow rate based on the first information. Referring to FIG. 14, an example of a calibration curve is provided, showing a relationship between a voltage and a flow rate. It will be understood that this calibration could alternatively be based on current, provided the device is not configured to keep current constant.

[0092] In some embodiments, this calculation may include subtracting, e.g., a reference voltage (or current) from the measured voltage (or current). For example, in FIG. 14, the flow curve is based on -([Voltage] -[Voltage at zero flow]). In some embodiments, [Voltage] is a single data point. In some embodiments, [Voltage] is an average of a plurality of data points.

[0093] The voltage (or current) signal may be analyzed using spectral methods to determine dominant frequencies of the fluid flow. This information may be used to evaluate, for example, performance of the system, the health of a pump, or the need for maintenance.

[0094] The mass and / or volumetric flow rate may be integrated over time to measure cumulative mass or volume past the substrate. The at least one processor may be configured to, collectively, transmit a rate of mass and / or volumetric flow and / or a cumulative mass of volume to one or more remote processors.

[0095] Referring to FIG. 10, a system may include various other components. For example, a system may include a fluid source 1000 providing a fluid whose flow rate is to be measured. The fluid may be directed to a sensor system 500 via, e.g., a pump 1010. The fluid may be controlled by one or more valves 1020. As shown, a pump and valve are shown upstream of the sensor system 500. However, any pump or valve may be located upstream and / or downstream of the sensor system 500. In some embodiments, the sensor system 500 may be configured to control at least one pump 1010. In some embodiments, the sensor system 500 may be configured to control at least one valve 1020. In some embodiments, the valve is controlled using pulse width modulation, in order to control the flow.

[0096] The system may also include one or more components 1030 downstream of the sensor system 500. This may include a container (e.g. , for the fluid to flow into). This may include a filter. This may include additional processing or manufacturing equipment. The one or more component 1030 may be located upstream of the sensor. Referring to FIG. 15, an illustration of a system can be seen. Such a system may be useful for, e.g., agriculture, water supply, HVAC, or other applications where a fluid is being distributed to multiple outlets.

[0097] In FIG. 15, a system 1500 may include a fluid source 1501. The fluid source may be coupled to a pump 1502. The fluid source may be operably coupled to a manifold 1503. The manifold may be, e.g., a pipe with a plurality of outlets. The fluid may be configured to pass from the manifold through a connection 1504, towards a flow sensor 100 and a fluid outlet 1508. A valve 1505 may be configured to control the amount of fluid to be directed towards the outlet. A coupling 1506 may be used to operably connect a flow sensor system to the manifold. The coupling may be connected to a first housing 510. The first housing may be coupled to a flow sensor 100 (such as to an upstream-facing surface of the flow sensor). A second housing 520 may be coupled to the flow sensor (such as to a downstream-facing surface of the flow sensor). The second housing may be coupled to a nozzle 1507, which may include the outlet 1508. The flow sensor may be sandwiched between the first housing and the second housing, and may be held together by, e.g., bolts 1509, or any other appropriate technique for holding the components together. In some embodiments, information from each flow sensor may be sent to one or more processors 1510.

[0098] In some embodiments, the a flow sensor may be coupled to an agricultural sprayer. For example, liquid fertilizer, pesticide, and / or fungicide may be provided to a plurality of nozzles, each nozzle coupled to a flow sensor as disclosed herein. In some embodiments, data from each flow sensor may be sent to a processor, that may use that information to control the valves and / or the pump. In some embodiments, the processor may generate an alert for a user if the data from one or more flow sensors is outside a target range. The alert may also be based on how many flow sensors are outside the target range. For example, if a single flow sensor is outside a target range, that may indicate one type of malfunction (e.g., aleak, a clogged nozzle, etc.). If multiple flow sensors are outside a target range, that may indicate a different type of malfunction (e.g., a problem in the manifold, etc.).

[0099] In various aspects, a method for determining cumulative flow of a fluid may be provided. Referring to FIG. 11, the method 1100 may include allowing 1110 a fluid to flow around or through a substrate, where at least one conductive wire is disposed within a stagnation region of the substrate.

[0100] The method may include passing 1120 a current through the at least one conductive wire such that it is heated up. This may include controlling the power to the wire(s) to ensure each wire operates with an overheat ratio a of between 1.01 and 5. As is known in the art, for hot wire anemometry, the wires may be operated using different modes, including a constant current mode, constant voltage mode, or a constant temperature mode.

[0101] Under constant current mode, the heating current across the wire is maintained constant. As the speed of the fluid increases, the hot wire cools, and the resistance of wire decreases. Tliis change can be monitored and correlated with, e.g, velocity, or volumetric flow rate for a given design.

[0102] Under constant voltage mode, the voltage between the top and bottom of a Wheatstone bridge is kept constant One leg of the Wheatstone bridge includes the ware and the voltage across the bridge can be monitored and correlated with, e.g., flow velocity, or volumetric flow' rate for a given design.

[0103] Under constant temperature mode, the voltage across the wire is controlled to keep the temperature of wire constant, to combat the cooling effect of the flowing fluid. The voltage can be monitored and correlated wdth, e.g. , velocity, or volumetric flow rate for a given design.

[0104] As such, the method may include measuring 1130 a voltage or current across the at least one conductive wire, or the voltage across a Wheatstone bridge. The method may include determining 1140 a flow rate from the voltage or current.

[0105] The method may include determining 1150 a cumulative mass and / or volume of fluid through the at least one conductive wire by integrating the determined flow rate over time.

[0106] The method may include adjusting 1160 a flow rate through the system. This may include adjusting 1161 at least one valve based on the flow rate. This may include adjusting 1162 at least one performance characteristic of a pump based on the flow rate.

[0107] The method may include measuring 1171 a voltage or current across at least one additional wire (configured for measuring temperature) in the stagnation region. The method may include determining 1172 a temperature within the fluid based on that determined cunent or voltage across at least one additional wire in the stagnation region.

[0108] The method may include measuring 1173 a voltage or current across at least two conductor elements in contact with the fluid. The method may include determining 1174 a conductivity or resistivity of the fluid based on a current or voltage across at least at least two conductor elements in contact with the fluid.

[0109] It will be understood that the different pairs of measurements and determinations (i.e., measuring / determining flow rate, measuring / determining temperature, measuring / determining conductivity) may be performed in any order, and may be performed in series or in parallel. Further, in some embodiments, the frequency of each pair of measurements / determinations may vary. Thus, in some embodiments, there is a 1:1 :1 correlation of measurements and determinations for flow rate:temperature: conductivity. However, in other embodiments, one or more determinations may be made more frequently than one or more other determinations. For example, flow rate may be determined more frequently than conductivity. Similarly, in some embodiments, there is a 1: 1 relationship between measurement and determination. That is, for every measurement of, e.g. , a wire used to monitor flow rate, there is a determination of flow rate. In some embodiments, a plurality of measurements may be used for a single determination. For example, in some embodiments, a wire may be monitored 3 times per second, and a flow rate may be determined that is based on all the three measurements.

[0110] In some embodiments, the sensitivity of the at least one conductive wire may be controlled by reducing a size of the stagnation region. This may be done in any way known to those of skill in the art.

[0111] For example, as seen in FIGS. 12A and 12B, a size of the stagnation region may be controlled by adjusting an angle of the substrate relative to a direction of fluid flow past the substrate. In some embodiments, an adjustable portion 1210 of the sensor (such as a sensor having a hinge 1211 around which the adjustable portion may rotate) can be adjusted to have a first configuration (FIG. 12 A) where the stagnation region (here, upstream stagnation region 431) is relatively large. This may be where the adjustable region is positioned such that a plane defining an upstream surface of the sensor is perpendicular to the general direction of flow 730. This may be when the adjustable portion is generally normal to an internal surface 711 of a housing 710. The adjustable portion 1210 may be adjusted to have a second configuration (FIG. 12B), such as one where the plane defining an upstream surface of the sensor is now at angled relative to the general direction of flow 730. The smaller the angle, the smaller the stagnation region.

[0112] Similarly, either via selecting a differently designed sensor, or by adjusting an opening using, e.g., a shutter such as that shown in FIG. 4F, the size of the stagnation region may be controlled by adjusting a location and / or size of an opening extending through the substrate. Substrates with openings having a larger cross-sectional area (i.e., more area for fluid to flow through the openings) will generally have smaller stagnation regions than substrates with less cross-sectional areas given to openings. Similarly, substrates with openings near the center of the substrate will generally have smaller stagnation regions than substrates with similar-sized openings near the outer edges of the substrate.

[0113] By selecting a differently designed sensor, the size of the stagnation region may be controlled by a shape of the substrate. Clearly, first substrates with more surface area preventing fluid from passing through it, will have larger stagnation regions. First substrates with smaller areas will have smaller stagnation regions.

[0114] Similarly, by adjusting the housing, the size of the stagnation region may be controlled. The size of the stagnation region may be controlled by the shape of a structure housing the substrate.

[0115] Various modifications may be made to the systems, methods, apparatus, mechanisms, techniques and portions thereof described herein with respect to the various figures, such modifications being contemplated as being within the scope of the invention. For example, while a specific order of steps or arrangement of functional elements is presented in the various embodiments described herein, various other orders / arrangements of steps or functional elements may be utilized within the context of the various embodiments. Further, while modifications to embodiments may be discussed individually, various embodiments may use multiple modifications contemporaneously or in sequence, compound modifications and the like.

[0116] Although various embodiments which incorporate the teachings of the present invention have been shown and described in detail herein, those skilled in the art can readily devise many other varied embodiments that still incorporate these teachings. Thus, while the foregoing is directed to various embodiments of the present invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof. As such, the appropriate scope of the invention is to be determined according to the claims.

Claims

What is claimed is:

1. A flow sensor, comprising: a first substrate having a first surface and a second surface opposite the first surface, the first surface being configured to face an upstream direction in a flow of a fluid, the second surface being configured to face a downstream direction in the flow of the fluid, the first substrate being configured to generate an upstream stagnation region extending upstream from the first surface and a downstream stagnation region extending downstream from the second surface; and at least one conductive wire disposed within the upstream stagnation region, the downstream stagnation region, or both, the at least one conductive wire being a distance d from the first substrate, where d > 0, the at least one conductive wire being operably coupled to circuitry on the first substrate.

2. The flow sensor of claim 1, wherein the circuitry consists of conductive leads.

3. The flow sensor of claim 1, wherein the at least one conductive wire is disposed within at least one sensor subcomponent, the at least one sensor subcomponent comprising a second substrate having a third surface and a fourth surface opposite the third surface, the third surface facing the first substrate, each second substrate having an opening extending from the third surface to the fourth surface, and the at least one conductive wire extending across the opening in a direction parallel to the third surface.

4. The flow sensor of claim 3, wherein the at least one conductive wire includes a plurality of conductive wires.

5. The flow sensor of claim 4, wherein the at least one sensor subcomponent includes a Wheatstone bridge.

6. The flow sensor of claim 4, wherein the at least one sensor subcomponent further comprises at least one additional wire configured to measure temperature.

7. The flow sensor of claim 4, wherein the at least one sensor subcomponent further comprises at least two conductor elements configured to contact the fluid.

8. The flow sensor of claim 4, wherein a distance separating each wire of the plurality of conductive wires from an adjacent wire is 0.1-25 times a width dimension of the wire.

9. The flow sensor of claim 8, wherein a width dimension of each conductive wire is 0.5 pm-40 pm, and the distance separating each conductive wires from an adjacent conductive wire is 0.5 pm-60 pm.

10. The flow sensor of claim 2, wherein all sensor subcomponents are disposed at a fixed distance <77 > 0 in a direction normal to the first surface of the first substrate.

11. The flow sensor of claim 2, wherein all sensor subcomponents are disposed at a fixed distance 72 > 0 in a direction normal to the second surface of the first substrate.

12. The flow sensor of claim 2, wherein at least one sensor subcomponent is disposed at a fixed distance <77 > 0 in a direction normal to the first surface of the first substrate, and at least one sensor subcomponent is disposed al a fixed distance <72 > 0 in a direction normal to the second surface of the first substrate.

13. The flow sensor of claim 1, wherein each of the at least one conductive wire has at least one dimension that is less than 1 pm.

14. The flow sensor of claim 1, wherein each of the at least one conductive wire has at least one dimension that is less than 0.3 pm.

15. The flow sensor of claim 1, wherein each conductive wire is configured to have a maximum deflection of less than 0.01% of its length throughout a predetermined operating range of velocities.

16. The flow sensor of claim 1, wherein a length-to-width aspect ratio of each conductive wire is 1 - 500.

17. The flow sensor of claim 1, wherein a length-to-width aspect ratio of each conductive wire is 5 - 500.

18. The flow sensor of claim 1, wherein each conductive wire has a rectangular crosssection.

19. The flow sensor of claim 1, wherein one or more of the at least one conductive wire comprises a pure metal or a metal alloy.

20. The flow sensor of claim 19, wherein each conductive wire is comprised of platinum.

21. The flow sensor of claim 1, wherein one or more of the at least one conductive wire comprises an electrically conductive polymer.

22. The flow sensor of claim 1, wherein one or more of the at least one conductive wire comprises a semiconductor material.

23. The flow sensor of claim 1, wherein one or more of the at least one conductive wire comprises two or more materials.

24. The flow sensor of claim 23, wherein each conductive wire is comprised of platinum and titanium.

25. The flow sensor of claim 1, wherein the at least one conductive wire is coated with a non-conductive material.

26. The flow sensor of claim 25, wherein the non-conductive material is a non-conductive polymer.

27. The flow sensor of claim 26, wherein the non-conductive polymer is parylene.

28. The flow sensor of claim 1, further comprising at least one opening extending from the first surface to the second surface of the first substrate.

29. The flow sensor of claim 28, wherein the first substrate comprises a plurality of openings, each opening extending from the first surface to the second surface.

30. The flow sensor of claim 1, further comprising at least one communications interface coupled to the circuitry.

31. The flow sensor of claim 1, wherein the flow sensor is configured such that each conductive wire has a temperature between 50°C and 500’C.

32. The flow sensor of claim 31, wherein the flow sensor is configured such that each conductive wire has a temperature that changes with flow rate of the fluid and is configured to be maintained more than 5°C warmer than a temperature of the fluid.

33. A flow sensor system, comprising: at least one housing through which a fluid is configured to flow; and a flow sensor of claim 1 operably coupled to the at least one housing such that fluid is configured to flow around, or through an opening in, the first substrate of the flow sensor.

34. The flow sensor system of claim 33, wherein the at least one housing includes at least a first housing and a second housing.

35. The flow sensor system of claim 34, wherein the first housing is operably coupled to an upstream surface of the flow sensor, and the second housing is operably coupled to a downstream surface of the flow sensor.

36. The flow sensor system of claim 35, further comprising a first o-ring between the first housing and the flow sensor, and a second o-ring between the second housing and the flow sensor.

37. The flow sensor system of claim 33, wherein at least a portion of the flow sensor is disposed within the at least one housing, and at least a portion of the flow sensor is disposed external to the at least one housing.

38. The flow sensor system of claim 33, wherein the flow sensor is disposed within the at least one housing.

39. The flow sensor system of claim 33, further comprising: a measuring circuit operably coupled to the at least one conductive wire configured to measure at least one of a voltage or a current; and a power circuit operably coupled to the at least one conductive wire configured to ensure each wire operates with an overheat ratio a of between 1.01 and 5.

40. The flow sensor system of claim 39, further comprising at least one processor operably coupled to the measuring circuit.

41. The flow sensor of claim 40, wherein the at least one processor is configured to, collectively, receive first information from the measuring circuit, the first information comprising a voltage and / or a current.

42. The flow sensor of claim 41, wherein the at least one processor is configured to, collectively, transmit the first information or representations of the first information to one or more remote processors.

43. The flow sensor of claim 41 , wherein the at least one processor is configured to, collectively, calculate a mass and / or volumetric flow rate based on the first information.

44. The flow sensor of claim 43, wherein the mass and / or volumetric flow rate is integrated over time to measure cumulative mass or volume past the substrate.

45. The flow sensor of claim 43, wherein the at least one processor is configured to, collectively, transmit a rate of mass and / or volumetric flow and / or a cumulative mass of volume to one or more remote processors.46 The flow sensor of claim 41, wherein the at least one processor is configured to perform a spectral analysis on the voltage or current signal to determine dominant frequencies of the fluid flow.

47. A method for determining cumulative flow of a fluid, comprising: allowing the fluid to flow around or through a substrate, where at least one conductive wire is disposed within a stagnation region of the substrate; passing a current through the at least one conductive wire such that it is heated up; measuring a voltage or current across the at least one conductive wire; and determining a flow rate from the voltage or current; and determining a cumulative mass and / or volume of fluid flow around or through the substrate by integrating the flow rate over time.

48. The method of claim 47, further comprising adjusting at least one valve based on the flow rate.

48. The method of claim 48, where the valve is adjusted using pulse width modulation.

49. The method of claim 47, further comprising determining a temperature within the fluid based on a current or voltage across at least one additional wire in the stagnation region.

50. The method of claim 47, further comprising determining a conductivity of the fluid based on a current or voltage across at least at least two conductor elements in contact with the fluid.

51. The method of claim 47, wherein sensitivity of the at least one conductive wire may be controlled by reducing a size of the stagnation region.

52. The method of claim 51, wherein the size of the stagnation region is controlled by adjusting an angle of the substrate relative to a direction of fluid flow past the substrate.

53. The method of claim 51, wherein the size of the stagnation region is controlled by adjusting a location and / or size of an opening extending through the substrate.

54. The method of claim 51, wherein the size of the stagnation region is controlled by a shape of the substrate.

55. The method of claim 51, wherein the size of the stagnation region is controlled by the shape of a structure housing the substrate.

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