Abstract: A flow metering apparatus possessing a housing with a chamber including and entrance and an exit for the passageway of fluid therethrough. A flow directing body is located in the chamber and includes first and second conical portions positioned on either side of a cylindrical portion. The body is supported in the chamber in a fixed manner. An orifice is located within the chamber upstream of the first conical portion of the body and is of a predetermined size to control the passage of fluid through the housing chamber. First and second sensors sense the dynamic pressures at the apex of the first conical portion and at a position between the body and a wall of the chamber.

Abstract: When a gas flow producer is driven, plural kinds of gases flow into a measure-passage at respective timing. An orifice is provided in the measure-passage. The orifice has a diameter-changing portion which restricts a separation of gases from an inner surface of the measure-passage. A pressure sensor is provided in the measure-passage to detect a pressure determined by the orifice and the gas flow producer. A microcomputer calculates a density ratio between the gases based on the detected differential pressure.

Abstract: The present invention relates to the field of correlating a fluid flow rate by strategically measuring a differential pressure of a fluid. Embodiments of the present invention build off a simple concept of applying an aerodynamic device into a flow stream in conjunction with a flow concentrator and measuring fluid pressure at two locations on the aerodynamic device. The flow meter has not moving parts other than used for making tuning adjustments in some embodiments. A central design approach with the present invention is that each component can be adjusted relative to the other. Unlike prior systems that utilize a necked-down region of a fluid passage, the current system increases fluid velocities around a centralized flow element with the aid of an aerodynamic flow horn. Head losses are minimized through this approach.

Abstract: An apparatus that couples automated injection with flow feedback to provide nanoliter accuracy in controlling microliter volumes. The apparatus comprises generally a source of hydraulic fluid pressure, a fluid isolator joined to the outlet of the hydraulic pressure source and a flow sensor to provide pressure-driven analyte metering. For operation generally and particularly in microfluidic systems the hydraulic pressure source is typically an electrokinetic (EK) pump that incorporates gasless electrodes. The apparatus is capable of metering sub-microliter volumes at flowrates of 1–100 ?L/min into microsystem load pressures of up to 1000–50 psi, respectively. Flowrates can be specified within 0.5 ?L/min and volumes as small as 80 nL can be metered.

Abstract: A connector (3) is suggested, which is capable of connecting a fluid line (28) to a fluid technology device. A connection channel runs between a device connection (24) and a line connection (25) in the connector (3). The connector (3) is equipped with a volume flow detection device (2) that has a mass flow sensor device (54), using which the volume flow through the connection channel (26) may be determined using a bypass channel (48).

Abstract: An apparatus and method for measuring gas flow rates and an improved automatic vehicle tire inflation system which utilizes the inventive gas flow measurement apparatus and method. The gas flow measuring apparatus and method utilize a porous media material effective for creating an appropriate pressure differential relative to the gas flow rate.

Abstract: The detector for monitoring decrease in air flow rate due to air filter clogging. It is based on combination of three essential components: the air flow sensor, a threshold detector and an indicator. The air flow sensor is built in form of a novel thermo-anemometer which contains a thermistor, a heating element, and a thermal insulator. Temperature of the sensor is maintained above the air temperature by a constant value by means of an electronic servo circuit. The threshold detector is implemented either in a hardware or software. A novel design of a thermo-anemometer (closely related to a hot wire anemometer) automatically compensates for variations in the air temperatures. The thermo-anemometer triggers the threshold circuit when air flow rate drops below a preset level. For reduction of power consumption, the detector may employ two additional sensors: one is for detection of the blower operation and the other is a presence detector to enable the alarm in presence of people to perceive the alarm.

Abstract: Volumetric flow meters, volumetric flow controllers, mass flow meters, and mass flow controllers using a transverse laminar flow assembly are described. The flow assembly may be constructed from a plurality of open and/or closed slices or layers stacked upon one another and held together in compression by through bolts or another means. Meter or flow controller accuracy may be aided by use of flow conditioning features preceding an axial bore of the transverse flow assembly including one or more of a deflector, filter and nozzle.

Abstract: A device for measuring the volume flow or other substance properties of a gas, whose direction of flow can reverse. The arrangement contains a specially designed Y-piece, which is used for branching into direction-dependent flow paths and can be used at the same time for the measurement. Such devices can be preferably used in the area of mechanical respiration.

Abstract: A pressure sensor for measuring a pressure of a process fluid includes a vessel, an electrode and a diaphragm. The vessel receives the process fluid. The electrode is integral with an inner wall of the vessel. The diaphragm extends at least partially over the electrode and is configured to move relative to the electrode in response to the pressure of the process fluid. An electrical capacitance between the electrode and the diaphragm is related to the pressure of the process fluid.

Abstract: An average bidirectional flow tube, including a body having two side plates and upper and lower plates, a partition plate installed to be perpendicular to the side plates of the body so that front and rear ends of the tube are separated from each other, and two pairs of pressure impulse lines installed at front and rear positions of the partition plate. The upper and lower plates of the body each have a curvature to be in contact with an inner surface of a pipe in which the average bidirectional flow tube is installed, and each of the pressure impulse lines is installed to communicate with an interior of the pipe. Although a two-phase flow occurs in the pipe or the flow of the fluid flowing in the pipe is changed, an average flow rate of a fluid can be measured. Particularly, it is easy to measure an average flow rate of the fluid when the fluid flows at a low speed. Further, even when sudden pressure reduction occurs in the pipe, an additional cooling device is not required.

Abstract: In a device for estimating an amount of intake air of an internal combustion engine, wherein an amount of intake air passing through the throttle valve is calculated by using of an upstream side intake air pressure upstream of the throttle valve and a downstream side intake air pressure downstream of the throttle valve, and an amount of intake air supplied into the cylinder is estimated on the basis of the amount of intake air passing through the throttle valve, the upstream side intake air pressure used at the time when the amount of intake air passing through the throttle valve is calculated is detected or calculated to take account of a pressure loss, produced by at least an air-cleaner, from the atmospheric pressure.

Abstract: An orifice plate for use in a conduit through which fluid flows is defined by a central circular region having a radius R0 and a ring-shaped region surrounding the central circular region. The ring-shaped region has holes formed therethrough with those holes centered at each radius R thereof satisfying a relationship AR=a/(XRVRb) where AR is a sum of areas of those holes having centers at radius R, XR is a flow coefficient at radius R, VR is a velocity of the fluid that is to flow through the conduit at radius R, b is a constant selected to make at least one process variable (associated with the fluid that is to flow through the conduit) approximately equal at each radius R, and a is a constant that is equal to (XRARVRb) at each radius R.

Abstract: Differential pressure measurement devices, installations and methods are disclosed, the devices including a main body and retainer. The main body is characterized by a front portion having a substantially constant curvilinear flow facing front surface, a rear portion, and a substantially constant diameter portion between the front portion and the rear portion. The rear portion includes relatively larger and smaller diameter termini. The installation of this invention is maintained in a fluid flow containing conduit and includes a pipe section affixed between sections of the conduit. The device is concentrically located in the otherwise unobstructed flow path defined by the pipe section, with the device retainer downstream of all measurement ports, and obstructs fluid flow thereat to establish annular flow therearound having predictable characteristics.

Abstract: Method and device for monitoring the flow speed of an infusion solution, such as with hemofiltration or hemodiafiltration. The device has a tube for conducting an infusion solution from a source of infusion solution to a pump device in the form of a metering pump, such as a peristaltic pump or a ceramic pump, and on to an infusion device, such as a drip chamber. The flow speed is determined by the metering pump. The flow speed is monitored separately in that the pressure across a restriction device in the tube is measured. The restriction device can be a separately arranged restriction valve. Alternatively the restriction device is arranged by the tube having a small internal diameter of the order of 0.5 mm in size. The pressure measuring device only needs to measure the absolute pressure with respect to the atmosphere. The hydrostatic pressure due to the infusion bag being hung above the pump and the pressure meter is subtracted in a calculation device.

Abstract: A method of obtaining at least one representation of a characteristic function of a sensor from a test fluid during calibration of the sensor according to a sensor model having a transfer function operating on flow rate, at least one sensor property and at least one fluid property and employing the at least one representation of the characteristic function to determine flow rates through the sensor during operation with an arbitrary fluid.

Abstract: A respiratory tract differential-pressure flow sensor, including a tube having a distal end that is insertable into a respiratory tract, an interfering body disposed within the tube proximal to the distal end and having a first edge facing one end of the tube and a second edge facing away from the end, the interfering body extending across the diameter of the tube, a first pressure sensing port operative to sense an air pressure, the first port being disposed in the first edge not abutting the wall of the tube, and a second pressure sensing port operative to sense an air pressure, the second port being disposed in the second edge not abutting the wall of the tube, where either of the edges is inclined inwardly towards the axis of the interfering body extending across the diameter of the tube.

Abstract: The invention is directed to a device for obtaining flow rate measurements including a sensor assembly and a housing. The sensor assembly includes a body defining a first fluid flow passage having an inlet, an outlet, a flow restricting element in the first fluid flow passage between the inlet and the outlet, an upstream fluid pressure sensor, a downstream fluid pressure sensor, an upstream signal contact connected to the upstream fluid pressure sensor, and a downstream signal contact connected to the downstream fluid pressure sensor. The housing has an upstream portion defining an upstream port, a downstream portion defining a downstream port, and a probe access port configured to provide access of a probe to at least one of the upstream signal contact and downstream signal contact. The housing can also define a second fluid flow passage in parallel with the first fluid flow passage. The device can be disposable.

Abstract: A pressure transducer and method for measuring pressure of a fluid flow in a tube include use of a sensing tube through which the pressurized flow passes. The sensing tube deforms outward in response to the pressurized flow within. Deformation measuring devices, such as strain gages, measure the outward deformation and allow computation of the pressure of the flowing fluid. A housing surrounds the sensing tube to relieve stresses on the sensing tube, to prevent damage to the sensing tube, and to contain any rupture of the sensing tube. The sensing tube may have a round, rectangular, or other shape cross-section. The pressure transducer allows continuous and non-invasive measurement of pressure inside a tube. In addition, a flow restriction such as an orifice may be provided in the sensing tube to enable a flow rate to be determined from the pressure drop across the flow restriction.

Abstract: An object of the present invention is to provide a hydrocarbon gas flow rate adjusting method and apparatus, which suppress deterioration of an elastic foamed body with the passage of time and enables a stabilized adjustment of the flow rate for a long period by combining a fine porous film with a porous elastic foamed body. More specifically, fuel gas taken out of a tank which stores hydrocarbon fuel gas in liquid phase is controlled in its flow rate such that the upper limit of the flow rate is the maximum flow rate obtained by depressurizing the fuel gas with a flow rate restricting member as a first stage and then adjusting to an arbitrary flow rate within a range of the restricted maximum flow rate with an adjustable flow rate adjusting member.

Abstract: An airway adaptor that includes a tubular body having a first gas flow passage defined therein. A protrusion extends from an interior wall of the tubular body into the gas flow passage. The protrusion includes a distal end portion spaced apart from the interior wall of the tubular body, and a second gas flow passage defined through the protrusion. An inlet to the second gas flow passage is provided at the distal end portion of the protrusion, and an outlet of the second gas flow passage is provided at an exterior portion of the tubular body. A pair of sidewalls are disposed on the distal end portion of the protrusion. Each sidewall is generally parallel to a direction of a flow of gas through the first passage. The inlet of the second gas flow passage is disposed between the pair of sidewalls.

Abstract: A fluid-flow measuring ball valve includes a replaceable ball within a housing. The replaceable ball includes a flow restriction calibrated to the characteristics of the fluid. Pressure ports on either side of the ball provide for obtaining pressure readings which can be used to determine fluid flow.

Abstract: An magnetic flow meter is provided which includes a reference electrode configured to electrically couple process fluid flowing within a flowtube of the flow meter. The reference electrode is adapted to measure potential of the process fluid. A current limiter is configured to limit current flow through the reference electrode and thereby reduce corrosion of the reference electrode.

Abstract: A flow sensor is disclosed that measures a flow of fluid passing through a conduit and a flow resistive element for use in such a flow sensor. The flow sensor includes a housing having a main channel defined therethrough. A flow resistive element is disposed in the housing across the main channel. The flow resistive element includes a rigid body member having a first surface and a second surface. A plurality of unobstructed, wedge-shaped, openings are defined in the body member and extend through the rigid body member. In addition, a plurality of spokes extend from a central portion of the body member to its perimeter so that each spoke separates adjacent wedge-shaped openings from one another.

Abstract: A restriction flowmeter including a cylinder through whose interior a fluid to be measured flows and a pipe for forming a restriction structure penetrating the cylinder in a direction perpendicular to the central axis of the cylinder, the pipe having a diameter smaller than the inner diameter of the cylinder, characterized in that a first pressure measuring hole is formed on the most restricted cross section perpendicular to the flow direction and a second pressure measuring hole is formed on a wall of the cylinder located upstream which is away from the most restricted cross section by ½ or more of the inner diameter of the cylinder.

Abstract: A flow monitor is removably connectable in serial fluid communication with a coolant conduit of an engine cooling system. By providing a flow restrictor between upstream and downstream ports, a differential pressure is created between the upstream and downstream ports. The measured magnitude of this differential pressure allows a microprocessor, or similarly configured component, to determine the actual flow rate of the coolant passing through the coolant conduit between the upstream and downstream pressure sensing ports. In this way, actual flow is measured to indicate the proper operation of the cooling system.

Abstract: A method of determining an inlet flow rate (Finlet) of a flowable material including passing an inlet stream of flowable material through a chamber (20) having an outlet aperture (100); measuring a first rate of change of quantity of material in the chamber (20) when the material is entering at said inlet flow rate; measuring a second rate of change of quantity if material in the chamber (20) when no material is entering the chamber (20); and calculating the inlet flow rate (Finlet) from said first and second rates, wherein both rate measurements are made while the whole of the outlet aperture (100) of the chamber (100) of the chamber (20) is occupied by the flowable material.

Abstract: Methods and apparatus for a bi-directional dual chamber orifice fitting comprising a body with a chamber in fluid communication with a flow bore. The fitting also comprises an orifice supported by an orifice plate carrier that is selectably disposable in the bore. In the preferred embodiment, the lower chamber includes two passageways connecting the chamber to the flow bore. One passageway is located on either side of the orifice plate. Each passageway may also be equipped with a check valve to permit flow in only one direction through the passageway. In operation, the passageway on the upstream side of the orifice would allow fluid to flow into the lower chamber while the passageway on the downstream side would prevent flow back into the flow bore.

Abstract: A flow direction detector is provided which includes a flow disruptor positioned in a fluid flow path to effect a detectable differential flow characteristic to such flow path based on fluid flow direction, and a sensor arrangement configured to detect such detectable differential flow characteristic within the flow path.

Abstract: Devices and methods for enabling measurement of a selected fluid characteristic in fluid flowing through a conduit. The device includes a body connected in the conduit having an accelerator section and a flow conditioner section within which a measuring unit such as an averaging pitot is maintained. The flow conditioner section includes a straight, substantially constant diameter conduit length selected to provide a settling distance after the accelerator section and in advance of the measuring unit sufficient to provide stabilization and linearization of the flowing fluid prior to measurement. Utilizing the device, repeatable and accurate measurement of the characteristic (flow rate for example) may be conducted over an operating range characterized by up to at least about a 25 to 1 turndown in flow with a constant flow coefficient independent of fluid flow velocity or Reynolds number.

Abstract: A mass flow meter device utilizing a housing having a wall portion forming a chamber with an entrance and exit for passing fluid through the same. A body is located within the chamber and is composed of a first conical portion, a second conical portion, and a cylindrical portion positioned intermediate the first and second conical portions. The body is held within the chamber in a standard or reverse direction. A first pressure probe or sensor measures the fluid pressure at the apex of the first conical portion while a second pressure probe or sensor obtains a second pressure measurement at the cylindrical portion of the body. The comparison of the first and second pressure measurements serves as an indication for the mass flow of fluid through the housing. The flow meter device may be adapted to existing fluid sources such as aerosol generators.

Abstract: A differential pressure flow rate measurement apparatus comprises: a conduit having a flow passage for conveying a fluid flow, the conduit being adapted for connection to a downhole fluid flow line having a bore of predetermined transverse cross-sectional area; a flow energy dissipator which partially obstructs the flow passage and which is capable of imparting an angular velocity to the fluid flow and thereby causing a dissipative pressure drop in the fluid; and a pressure sensor for measuring said pressure drop. The flow passage, when viewed in the axial direction of the flow passage, projects an unobstructed transverse cross-sectional area which is at least 25% of the transverse cross-sectional area of said bore.

Abstract: An instrument used to control fluid flow. The instrument has a flow restrictor between an inlet and an outlet. First and second multisensor have sensing surfaces in the inlet and outlet that sense pressures and temperatures of the fluid flow. A circuit generates a mass flow output based on a difference between the pressure in the inlet and the pressure in the outlet. The mass flow output including a temperature correction as a function of at least one of the sensed temperatures in the inlet and outlet.

Abstract: A method and apparatus includes a multi-position valve that restricts the air flow when the valve is placed in one position. Pressure tap valves are located are the inlet and outlet ports to measure the pressure differential and thereby determine the airflow rate.

Abstract: An object of the present invention is to provide a hydrocarbon gas flow rate adjusting method and apparatus, which suppress deterioration of an elastic foamed body with the passage of time and enables a stabilized adjustment of the flow rate for a long period by combining a fine porous film with a porous elastic foamed body. More specifically, fuel gas taken out of a tank which stores hydrocarbon fuel gas in liquid phase is controlled in its flow rate such that the upper limit of the flow rate is the maximum flow rate obtained by depressurizing the fuel gas with a flow rate restricting member as a first stage and then adjusting to an arbitrary flow rate within a range of the restricted maximum flow rate with an adjustable flow rate adjusting member.

Abstract: A flow sensor package with a housing, a pressure sensing element, a restriction, and an elastomeric seal. The housing has a base, a cover, an inlet port, an outlet port, and first and second channels. The first and second channels are in parallel between the inlet port and the outlet port. The pressure sensing element is in the first channel and the restriction is the second channel. The elastomeric seal engages the pressure sensing element to prevent flow of a fluid, which may be a liquid, through the first channel. The elastomeric seal has a conductive path from the pressure sensing element to a lead, which extends outside the housing.

Abstract: The invention is directed to a device for obtaining flow rate measurements including a sensor assembly and a housing. The sensor assembly includes a body defining a first fluid flow passage having an inlet, an outlet, a flow restricting element in the first fluid flow passage between the inlet and the outlet, an upstream fluid pressure sensor, a downstream fluid pressure sensor, an upstream signal contact connected to the upstream fluid pressure sensor, and a downstream signal contact connected to the downstream fluid pressure sensor. The housing has an upstream portion defining an upstream port, a downstream portion defining a downstream port, and a probe access port configured to provide access of a probe to at least one of the upstream signal contact and downstream signal contact. The housing can also define a second fluid flow passage in parallel with the first fluid flow passage. The device can be disposable.

Abstract: The invention is directed to a device for obtaining flow rate measurements including a sensor assembly and a housing. The sensor assembly includes a body defining a first fluid flow passage having an inlet, an outlet, a flow restricting element in the first fluid flow passage between the inlet and the outlet, an upstream fluid pressure sensor, a downstream fluid pressure sensor, an upstream signal contact connected to the upstream fluid pressure sensor, and a downstream signal contact connected to the downstream fluid pressure sensor. The housing has an upstream portion defining an upstream port, a downstream portion defining a downstream port, and a probe access port configured to provide access of a probe to at least one of the upstream signal contact and downstream signal contact. The housing can also define a second fluid flow passage in parallel with the first fluid flow passage. The device can be disposable.

Abstract: A differential-pressure flow sensor for airflow measurement in the presence of water condensation, for use with mechanical ventilators. The pressure-sensing ports at either end of the interfering body are displaced from the inner surface of the surrounding tubing, so as to prevent obstruction of the pressure-sensing ports by free flowing condensed water. The leading edge of the interfering body is angulated so as to deflect airflow towards the pressure-sensing port on the trailing edge of the interfering body, thereby flushing water droplets away from the port. The sides of the interfering body are sloped so as to generate turbulent boundary layer airflow at areas distant from the pressure-sensing ports, thereby encouraging water condensation away from the ports.

Abstract: A restriction flowmeter including a cylinder through whose interior a fluid to be measured flows and a pipe for forming a restriction structure penetrating the cylinder in a direction perpendicular to the central axis of the cylinder, the pipe having a diameter smaller than the inner diameter of the cylinder, characterized in that a first pressure measuring hole is formed on the most restricted cross section perpendicular to the flow direction and a second pressure measuring hole is formed on a wall of the cylinder located upstream which is away from the most restricted cross section by ½ or more of the inner diameter of the cylinder.

Abstract: A flowmeter is provided for measuring the flow rate of liquids, particularly liquids with solids suspended therein, or corrosive liquids, by measuring a flow without any contact between the sensing elements of the flowmeter and the liquid. The flowmeter is connected to upstream piping and downstream piping. Interconnected with the upstream piping is a first expansion joint, a tapered nozzle and a second expansion joint of smaller diameter. Extending from the second expansion joint is a reversed tapered nozzle connected to the downstream piping. One or more strain gauges, or a strain gauge assembly, is interconnected with the second expansion joint. The force of flow on the tapered nozzle creates a higher velocity flow within the tapered nozzle and then an expansion thereafter. This tends to urge the expansion nozzle, and the second expansion joint connected thereto, towards the upstream piping. Such movement is measured by th7e strain gauges.

Abstract: A flow meter and electrically operable valve assembly having integral flow meters provide detection of very low water flows, along with ease of installation and compact packaging for a water supply control system. The flow detection is particularly useful for systems that control household water supplies to prevent flooding, but is also useful in other applications such as agricultural and industrial systems where low water flow rates must be determined. All of the controls and features are integrable within a compact package that occupies essentially the same volume and piping space as a conventional electrically operable valve.

Abstract: An instrument used to control fluid flow. The instrument has a flow restrictor between an inlet and an outlet. First and second multisensor have sensing surfaces in the inlet and outlet that sense pressures and temperatures of the fluid flow. A circuit generates a mass flow output based on a difference between the pressure in the inlet and the pressure in the outlet. The mass flow output including a temperature correction as a function of at least one of the sensed temperatures in the inlet and outlet.

Abstract: A flow sensor for an analytical instrument. The flow sensor can be used to detect the flow of a fluid such as purge gas in the instrument. The sensor can measure the fluid flow at an opening of the instrument enclosure. The sensor has first and second differential pressure switches connected in series. The sensor has a sealed chamber which is in the opening. Bordering the sealed chamber are first and second restrictors through which the fluid can flow. A sensing tube transfers the pressure in the sealed chamber to the first and second switches.

Abstract: A device for measuring the flow of a fluid has a primary duct and a bypass arranged in series to the primary duct. The bypass has a first section and a second section. A baffle plate with a hole for the passage of the fluid is arranged in the first section. The second section comprises two parallel secondary ducts. In the first section, a turbulent flow dominates, while the flow in the second section is primarily laminar. If the turbulent effects in the bypass are sufficiently strong, the ratio of the flows in the primary duct and the bypass can be substantially independent of the fluid properties and of the flow rate. By using two parallel secondary ducts in the second section, high flow rates and therefore strongly turbulent effects can be achieved without exceeding the measuring range of the sensor.

Abstract: The invention relates to apparatus wherein an existing valve in a pipeline for carrying fluids such as water e.g. in a water distribution system can be connected, permanently or temporarily, to an electronics unit such that when the electronics unit is connected, the flow direction and flow rate of the water can be determined.

Abstract: A method and apparatus includes a multi-position valve that restricts the air flow when the valve is placed in one position. Pressure tap valves are located are the inlet and outlet ports to measure the pressure differential and thereby determine the airflow rate.

Abstract: A respiratory flow sensor, which is suitable for use near a patient, covers a broad gas volume flow measuring range with a low breathing flow resistance and good, reproducible measured signal quality at the same time. The respiratory flow sensor has a first air resistance body (3) with a blunt end and with an opposite pointed end. The air resistance body (3) is arranged between the measuring transducer (5), of which there is at least one, and the patient-side end (P) of the respiratory flow sensor. The pointed end of the first air resistance body (3) points toward the measuring transducer (5). A second air resistance body (4) with a pointed end is arranged between the measuring transducer (5), of which there is at least one, and the end of the respiratory flow sensor that is away from the patient. The pointed end of the second air resistance body (4) also points toward the measuring transducer (5).

Abstract: An airflow detection system for a vehicle paint booth. The vehicle paint booth has a first zone and a second zone adjacent to the first zone. An air velocity sensor measures airflow passing between the first zone and the second zone. An air deflector having at least one air deflection surface is located near the flow velocity sensor. At least one air deflection surface directs the airflow toward the flow velocity sensor to improve the reliability of the airflow detection system.

Abstract: There is provided a multi-stage variable orifice flow obstruction sensor for measuring a fluid flow. The sensor comprises a body member having an aperture therethrough. Moreover, a cover member is engaged to the body member and is disposed within the aperture. The cover member is adapted to transition between open and closed positions with respect to the aperture. Additionally, a flow-limiting obstruction member is engaged to the body member and is disposed within the aperture adjacent the cover member. The flow-limiting member is configured to apply a generally opposing force to the cover member when the cover member extends to the open position and contacts the flow-limiting member. By doing so, a pressure differential of the fluid may be sensed such that the fluid flow can be measured therefrom.