Abstract: A gas sensor with improved sensitivity. The gas sensor comprises an active sensor unit, a reference sensor unit and a temperature control circuit. The active sensor unit has an active detector. The reference sensor unit has a reference detector. The temperature control circuit is provided and configured to keep a detector at a predetermined temperature.

Abstract: A flow control apparatus comprising a housing capable of receiving a portion of the feeding set, a pumping device configured to receive the feeding set and may produce a fluid flow in the feeding set and deliver fluid to a subject, an ultrasonic sensor may be configured to produce a sensor signal indicative of a condition of the feeding set, and a control circuit in communication with the ultrasonic sensor for receiving the sensor signal from the ultrasonic sensor indicative of the condition of the feeding set. The ultrasonic sensor may comprise a plurality of sensor components which may be configured to emit an ultrasonic signal in a first direction, and in a second direction opposite the first direction through the feeding set.

Abstract: An apparatus for calculating a thermal conductivity of a gaseous substance is provided. The apparatus includes a substrate; a cover member disposed on the substrate, wherein the cover member comprises a flow tunnel for the gaseous substance; a flow sensing element disposed on the substrate, wherein the flow sensing element is exposed to the gaseous substance in the flow tunnel; and a pressure sensing element disposed on the substrate, wherein the pressure sensing element is exposed to the gaseous substance in the flow tunnel.

Abstract: A decrease in the accuracy after switching of the heating state can be reduced. The physical quantity detecting device includes: a flow rate detecting unit configured to include a heating element to measure a flow rate of a fluid to be measured; a heating element control unit configured to switch a control state of the heating element to any one of a heating state and a heating suppression state; and a signal processing unit configured to process a measured value of the flow rate detecting unit. When the heating element control unit switches the control state, the signal processing unit processes an estimated value determined based on a measured value of the flow rate detecting unit before the switching for a predetermined period immediately after the switching.

Abstract: A thermal flowmeter includes: a first thermal resistive element disposed on a pipe and sensing a first temperature of a fluid; a second thermal resistive element disposed on the pipe downstream relative to the first thermal resistive element and sensing a second temperature thereof; a control unit causing the second thermal resistive element to generate heat so that the second temperature is kept higher than the first temperature by a predetermined value; a power measurement unit measuring a power supplied to the second thermal resistive element; a temperature difference gradient calculation unit calculating a gradient of a difference between the second and first temperatures; a power compensation unit compensating the measured power based on the gradient of the difference and a value of the power when no fluid is in the pipe; and a flow rate calculation unit calculating a flow rate of the fluid based on the compensated power.

Abstract: A method of detecting airflow blockage of a transport refrigeration system including the steps of: activating a heater powered by an electric generation device; measuring an output voltage of the electric generation device; determining a predicted heat output of the heater in response to the output voltage; determining a predicted temperature rise across the heater in response to the predicted heat output; detecting a measured temperature rise across the heater; and determining an airflow reduction percentage in response to the predicted temperature rise across the heater and the measured temperature rise across the heater.

Abstract: An apparatus for measuring airflow in an airstream includes a generally planar panel adapted to be placed in the airstream so that air passes over opposite surfaces of the panel. The panel includes at least one slot that extends through the panel. A hot-point element is mounted on one of the panel surfaces adjacent the at least one slot. The at least one slot is configured to permit air passing over the opposite surfaces to pass through the slot and become mixed together. The hot-point element is positioned on the panel so that the mixed air passes over the hot-point element.

Abstract: A sensor for sensing a flow rate of a fluid comprises an upstream resistive element having a first resistance that changes with temperature, a downstream resistive element having a second resistance that changes with temperature, at least one tail resistor configured to determine thermal conductivity of the fluid, at least one pressure sensor configured to determine a differential pressure in the flow direction of the fluid, and circuitry configured to use the differential pressure with the thermal conductivity to determine a kinematic viscosity of the fluid, and compensate an output of the bridge circuit. The downstream resistive element is situated downstream of the upstream resistive element in the flow direction of the fluid, and the upstream resistive element and the downstream resistive element are operatively connected in a bridge circuit.

Abstract: The accurate measurement of inspired and expired gas volume flow and gas composition are important in respiratory therapy. The invention provides a gas flow sensor for a ventilator comprising: a flow path extending between a first end that connects to a supply of gas and a second end that couples to a patient airway interface; and a constant temperature anemometer sensor arranged within the flow path between those ends. It further comprises a sampling port that may be coupled to a gas analyser device; and an orifice which is in fluid communication with the flow path and the sampling port so that, in use, gas may be drawn from the flow path for analysis, the gas being drawn from the flow path at a position located between the anemometer sensor and the first end.

Abstract: Controlling an exhaust hood system having multiple hood sections each with an exhaust output having an associated damper, each exhaust output feeding to a common downstream fan, where damper position and fan speed control an exhaust flow rate through each hood section, involves monitoring at least one condition of each hood section and, based upon the monitoring, establishing a target flow rate for each hood section; based upon a sum of the target flow rates, establishing a fan speed; and monitoring an actual flow rate through each hood section and responsively controlling damper position to achieve the target flow rate for the hood section. Adjusting fan speed and damper position until damper position for at least one hood section achieves a predetermined open position, while at the same time each hood section satisfies its associated target flow rate, can reduce energy costs associated with system operation.

Abstract: A technique for calibrating a fluid flow sensor includes generating fluid flow at a first speed. A first temperature of the fluid flow is determined using a first temperature sensor that is positioned upstream of the fluid flow sensor. A first power is supplied to a main heater of the fluid flow sensor to adjust a second temperature of a first plate of the fluid flow sensor to be substantially equal to the first temperature, A second power is supplied to a guard heater of the fluid flow sensor to adjust a third temperature of a second plate of the fluid flow sensor to be substantially equal to a fourth temperature of the first plate. The first and second plates are separated by a spacer and the first speed and the third temperature provide a calibration point on a calibration curve for the fluid flow sensor.

Abstract: A digitally based resistance element and a processor are used with a hotwire to provide a mass airflow (MAF) sensor. A temperature sensor can provide an input to the processor which can provide signals to the digital based resistance element. The digital based resistance element may be on a first leg of a Wheatstone bridge, the hotwire on a second leg. The output of the hotwire may be provided to the processor which can modify the output such as to more closely approximate a MAF curve, and/or to address step changes initiated by the digital based resistive element.

Abstract: A fluid flow sensor that utilizes hot-wire anemometry and is a small, light weight, cost effective, easily manufactureable, and low power consuming device. The fluid flow sensor operates by exposing a hot wire loop to a fluid stream such that the amount of heat lost to fluid convection is a function of one or more fluid-related parameters (e.g., fluid speed, fluid type, fluid density, etc.). The heat loss affects the resistance in the wire loop, which can then be used to estimate the fluid speed or other fluid-related parameter. According to an exemplary embodiment, the fluid flow sensor includes one or more wire loops that are made from pre-formed wires and are wire bonded, micro-welded or otherwise non-monolithically attached to a substrate that may or may not include embedded sensor circuitry.

Abstract: A thermal flow rate sensor is provided which includes a main flow path through which a fluid flows, and a sensor flow path that branches off from the main flow path so as to cause the fluid to flow in a split flow and that is provided with a flow rate detecting mechanism configured to detect a flow rate of the fluid. The flow rate detecting mechanism includes an upstream-side coil and a downstream-side coil, each configured by using a heat-generating resistance wire wound around a sensor flow pipe forming the sensor flow path. A peak position of a temperature distribution generated in the sensor flow path by the upstream-side coil and the downstream-side coil is positioned on the upstream-side coil side relative to the middle position between the upstream-side coil and the downstream-side coil on the sensor flow path.

Abstract: Provided are a flowmeter that can measure a flow rate of a liquid with high accuracy and that is easy to carry and handle, and a dialysis machine and a medicinal solution injection device that employ the flowmeter. A flowmeter includes a tube connection member and a measurement instrument body. The tube connection member includes a tube-shaped body, a plurality of resonators that are arranged with gaps there between on an inner wall surface of the body, resonator-side antennas that are connected to the plurality of resonators and a heating element that is arranged between the pluralities of resonators. The measurement instrument body includes measurement-instrument-side antennas, temperature measurement units that are connected to the measurement-instrument-side antennas and measure a temperature, and a flow rate calculation unit that calculates a flow rate on the basis of the temperatures measured by the temperature measurement units.

Abstract: The invention relates to a submillimeter-sized hot-wire sensor (1) comprising a substrate (10), two support rods (11, 12), a metal wire (13) extending between the two ends of the support rods (11, 12), and electrical contacts (14, 15) disposed on the support rods, said contacts each being linked to one of the ends of the wire (13). The metal wire comprises at least two layers of metal materials, one of said layers being made of a material exhibiting a residual stress under tension and the other layer being made of a material exhibiting a residual stress under compression. The thicknesses of these metal layers are adapted so as to compensate the residual stresses between the various layers.

Abstract: A particulate filter is provided. The particulate filter includes: a plurality of sensors located in the filter; and a controller operatively connected to the sensors to determine a relative flow velocity over the sensors. A method for detecting obstructions in a filter may also be provided. The method may include: locating a sensor in a zone within a filter; connecting the sensor to a controller; monitoring the sensor with the controller; and determining whether the zone is obstructed based on data received from the sensor.

Abstract: A method and system for measuring a flow profile in a portion of a flow path in a turbine engine is provided. The system includes a mass flow sensor assembly having a plurality of hot wire mass flow sensors, the mass flow sensor assembly disposed in the portion of the flow path at a location where the flow profile is to be measured. The system also includes a controller that converts signals from the temperature sensor, the pressure sensor and the plurality of hot wire mass flow sensors to flow profile measurements.

Abstract: Provided is a compact apparatus for measuring the flow rate of a fluid. The apparatus includes a heated measure element and a heated reference element which are in substantially the same thermal environment within a measure cell, except that the measure element is situated in the path of the cooling fluid flow and the reference element is sheltered from this direct fluid flow. These elements are arranged as parallel and concentric planar elements that are essentially identical to each other with matching thermal characteristics. The elements are electrically connected in a Wheatstone bridge arrangement. Thermal exchange between the reference and measure elements is used to optimise noise rejection due to common mode background thermal effects. Measured parameters from the bridge can be used to derive the fluid flow rate.

Abstract: A mass flow controller among other embodiments and method is described. The mass flow controller including a thermal mass flow sensor including at least two sensing elements coupled to a sensor tube of the mass flow controller, the thermal mass flow sensor being designed to provide a first signal indicative of flow of a gas within a first flow-rate-range and a second signal indicative of flow of the gas within a second flow-rate-range; and a control portion figured to control a valve position of the mass flow controller responsive to the first signal when the flow of the gas is within the first flow-rate-range and control the valve position of the mass flow controller responsive to the second signal when the flow of the gas is within a second flow-rate-range.

Abstract: The present invention relates to an apparatus and method for measuring the convective heat transfer coefficients of nanofluids, which can realize a small-sized structure and can accurately control the movement velocity of a hot wire sensor within a fluid. The apparatus for measuring the convective heat transfer coefficients of nanofluids according to the present invention includes a sensor unit, a transfer unit and a liquid container. The transfer unit is formed on the sensor unit and is configured to allow the sensor unit to longitudinally reciprocate in a direction parallel to a ground surface with the sensor unit spaced apart from the ground surface. The liquid container is arranged below and spaced apart from the sensor unit, and is configured to allow a nanofluid or a base fluid, a convective heat transfer coefficient of which needs to be measured, to be put therein.

Abstract: The invention relates to a submillimeter-sized hot-wire sensor (1) comprising a substrate (10), two support rods (11, 12), a metal wire (13) extending between the two ends of the support rods (11, 12), and electrical contacts (14, 15) disposed on the support rods, said contacts each being linked to one of the ends of the wire (13). The metal wire comprises at least two layers of metal materials, one of said layers being made of a material exhibiting a residual stress under tension and the other layer being made of a material exhibiting a residual stress under compression. The thicknesses of these metal layers are adapted so as to compensate the residual stresses between the various layers.

Abstract: A particulate filter is provided. The particulate filter includes: a plurality of sensors located in the filter; and a controller operatively connected to the sensors to determine a relative flow velocity over the sensors. A method for detecting obstructions in a filter may also be provided. The method may include: locating a sensor in a zone within a filter; connecting the sensor to a controller; monitoring the sensor with the controller; and determining whether the zone is obstructed based on data received from the sensor.

Abstract: A corrosion resistant flow sensor apparatus includes a flow sensor including a micromachinable substrate mounted on a package substrate that includes electrically conductive traces and substrate bond pads. The flow sensor includes a MEMS sensing structure for sensing a mass flow parameter and sensor bond pads coupled to the sensing structure. The sensor bond pads include a top metal layer on a metal diffusion barrier layer including a metal diffusion barrier layer sidewall. Bond wires couple the sensor bond pads to the substrate bond pads. A housing including sides and a top portion is around the flow sensor and includes a flow channel having an inlet and an outlet. A multi-layer corrosion protection coating includes a nm scale adhesion layer and a self assembled monolayer (SAM) is on the adhesion layer. The protection coating covers the sensor bond pads including the metal diffusion barrier layer sidewall.

Abstract: An anemometer probe having a single wire or n wires (n>1) that are mutually parallel, for a measurement close to a wall, comprising, for each wire: a) two pins for holding the wire in place, the end of each pin having a flat zone for positioning and fastening the wire; and b) a straight portion of wire brazed onto said flat zones for positioning and fastening the wire.

Abstract: Provided is a compact apparatus for measuring the flow rate of a fluid. The apparatus includes a heated measure element and a heated reference element which are in substantially the same thermal environment within a measure cell, except that the measure element is situated in the path of the cooling fluid flow and the reference element is sheltered from this direct fluid flow. These elements are arranged as parallel and concentric planar elements that are essentially identical to each other with matching thermal characteristics. The elements are electrically connected in a Wheatstone bridge arrangement. Thermal exchange between the reference and measure elements is used to optimise noise rejection due to common mode background thermal effects. Measured parameters from the bridge can be used to derive the fluid flow rate.

Abstract: A value of a line-to-line resistor (24) is determined by subtracting a resistance value determined as a product of a voltage ratio based on divided voltages and a value of a reference resistor in a non-conductive state between a second electric wire (26) and a third electric wire (27) from a resistance value determined as a product of a voltage ratio based on the divided voltages and the value of the reference resistor in a conductive state therebetween. Once the value of the line-to-line resistor (24) is determined, it becomes possible to determine a compensated resistance value related to temperature.

Abstract: A robust sensor, such as a robust flow sensor or pressure sensor, is provided. In one illustrative embodiment, a robust flow sensor includes one or more flow sensor components secured relative to a membrane, and a substrate for supporting the membrane. In some cases, the one or more flow sensor components may be substantially thermally isolated from the substrate by the membrane. One or more wire bond pads may be situated adjacent to a first side of the substrate and may be provided for communicating signals relative to the one or more flow sensor components. A top cap may be situated adjacent to the first side of the substrate and secured relative to the substrate. The top cap may define at least part of a fluid inlet and/or an outlet of the flow sensor assembly, and may at least partially define a flow channel that extends from the inlet, past at least one of the one or more flow sensor components, and out the outlet of the flow sensor assembly.

Abstract: The flow rate measuring apparatus includes a connector portion, a main body portion, a bypass passage, a flow rate sensing element having a flow rate detection portion, a control circuit, a pair of metal terminals having end portions connected to a connector, embedded portions molded integrally with a resin portion constituting the main body portion, and exposed portions exposed in the main passage, which are connected to each other in a cascade manner, and a fluid temperature sensing element having a temperature sensing portion. The fluid temperature sensing element is arranged at a position apart from an outer wall surface of a side face of the bypass passage, and the temperature sensing portion is arranged at the center between the pair of metal terminals that are exposed in the main passage by the same length or between extension lines thereof.

Abstract: A process and system for detecting pluggage in a conduit that is feeding a solid and carrier gas to a flowing gas.

Abstract: An automatic clothes dryer comprises a cabinet defining an interior space in which is rotatably mounted a drum that defines a drying chamber, a heater assembly having a heating element for heating air, and a motor for rotating the drum. A blower is mounted within the interior space and is fluidly coupled to the drying chamber for moving heated air through the drying chamber. A first temperature sensor is mounted upstream of the heating element. A second temperature sensor is mounted downstream of the blower. Outputs from the temperature sensors are utilized with one or more methods to determine the air flow characteristics through the dryer.

Abstract: A corrosion resistant flow sensor apparatus includes a flow sensor including a micromachinable substrate mounted on a package substrate that includes electrically conductive traces and substrate bond pads. The flow sensor includes a MEMS sensing structure for sensing a mass flow parameter and sensor bond pads coupled to the sensing structure. The sensor bond pads include a top metal layer on a metal diffusion barrier layer including a metal diffusion barrier layer sidewall. Bond wires couple the sensor bond pads to the substrate bond pads. A housing including sides and a top portion is around the flow sensor and includes a flow channel having an inlet and an outlet. A multi-layer corrosion protection coating includes a nm scale adhesion layer and a self assembled monolayer (SAM) is on the adhesion layer. The protection coating covers the sensor bond pads including the metal diffusion barrier layer sidewall.

Abstract: An apparatus and method for adaptive materials arranged in a variety of orientations and with a wide range of attachment configurations to induce structural vibrations at extremely high frequencies. These mechanical vibrations cause fouling agents to become detached and accordingly “clean” an otherwise dirty element or wire of a hot-wire anemometer, planar or curvilinear sensor surface, or display surfaces. They also can be made to vibrate at such frequencies with such intensities that local droplets of water are either shaken off or instantaneously cavitate, thereby allowing the elements to be used in all weather conditions.

Abstract: There is provided a thermal type flow meter capable of accurately detecting a flow rate even when a fluid temperature varies rapidly or when the fluid temperature is high. A probe includes: a first main heating resistor; a second main heating resistor set at a temperature different from that of the first main heating resistor; and a sub-heating resistor for heating lead wires of the two main heating resistors. A CPU of a sensor control circuit finds a fluid temperature by using the two main heating resistors, and finds a fluid flow rate by using at least one of the two main heating resistors.

Abstract: The flow rate measuring apparatus includes a connector portion, a main body portion, a bypass passage, a flow rate sensing element having a flow rate detection portion, a control circuit, a pair of metal terminals having end portions connected to a connector, embedded portions molded integrally with a resin portion constituting the main body portion, and exposed portions exposed in the main passage, which are connected to each other in a cascade manner, and a fluid temperature sensing element having a temperature sensing portion. The fluid temperature sensing element is arranged at a position apart from an outer wall surface of a side face of the bypass passage, and the temperature sensing portion is arranged at the center between the pair of metal terminals that are exposed in the main passage by the same length or between extension lines thereof.

Abstract: An airflow speed detection device for measuring an airflow speed includes an airflow speed switch, and a connector. The airflow speed switch includes a detection head, and an elastic piece. The connector is electrically connected to the testing the airflow speed switch to connect an indicator to indicate close and open states of the airflow speed switch. If the airflow speed is not faster than a critical value, the elastic piece contacts the detection head to close the airflow speed switch. If the airflow speed is faster than the critical value, the elastic piece is blown away from the detection head to open the airflow speed switch.

Abstract: A heater chip (4) as a heat generation element is secured to the surface on the periphery of piping (2). Further, a temperature sensor chip couple (6) is placed on the surface on the periphery of the piping (2), along the direction of flow of fluid flowing in the piping (2). One (6a) of the sensor chips in the couple is placed on the upstream side of the heater chip (4) and the other (6b) is placed on the downstream side of the heater chip (4). The heater chip (4) and the temperature sensor chips (6a, 6b) are formed in a chip type. The temperature sensor chips (6a, 6b) as the pair are placed at positions spaced by the same distance from the heater chip (4).

Abstract: A value of a line-to-line resistor (24) is determined by subtracting a resistance value determined as a product of a voltage ratio based on divided voltages and a value of a reference resistor in a non-conductive state between a second electric wire (26) and a third electric wire (27) from a resistance value determined as a product of a voltage ratio based on the divided voltages and the value of the reference resistor in a conductive state therebetween. Once the value of the line-to-line resistor (24) is determined, it becomes possible to determine a compensated resistance value related to temperature.

Abstract: A thermal flow meter corrects flow rate detection errors produced by vaporization of liquid phase components included in a gas to be measured. The thermal flow meter includes a correction circuit 500 that applies respectively different predetermined voltages to heating resistors consisting of first heating resistor Rh1 and second heating resistor Rh2 of a sensor element disposed in the gas to be measured to set a first temperature state and a second temperature state, calculates a first flow rate value Q1 of the gas to be measured in the first temperature state and a second flow rate value Q2 of the gas to be measured in the second temperature state, and calculates a flow rate correction value ?Q based on a ratio (Q1/Q2) between the first flow rate value and second flow rate value or a fourth-power value (Q1/Q2)4 of the ratio to correct a flow rate of the gas to be measured.

Abstract: Systems and methods are described for application of a transitory corrective modification to a hot-wire anemometer flow voltage and/or calculated flow rate to compensate for transient thermal response of the anemometer during a change in mixture of a mixed gas being measured. According to one embodiment a method of applying the transitory corrective modification is provided. An output signal of an exhalation flow sensor of a medical ventilator is received. The flow sensor includes a hot-wire anemometer. The output signal is indicative of a rate of flow of expired gas by a patient. Transient thermal response of the hot-wire anemometer is compensated for by applying a corrective modification to the output signal or a value based thereon. The corrective modification is based at least in part on a fraction of inspired oxygen (FiO2) being supplied by the medical ventilator to the patient.

Abstract: An electrically heated, flexible fluid conduit or tube (40) includes an elongate, flexible tube body (42) defining a fluid flow path L (44) having a length (L) extending along a longitudinal axis (46). The tube body (42) includes an electrical resistance heater (48) surrounding the fluid flow path (44) over the length (L). The electrical resistance heater (48) has a heat output per unit length per voltage applied that does not vary when the tube body (42) is cut to different lengths.

Abstract: A system, flow meter, and method for measuring gas flow information, such as respiratory information. In an exemplary embodiment, the flow meter may include a cylindrical body that allows the respiratory gas to flow through and at least one hot wire disposed within the cylindrical body. Further, the flow meter may include a bridge circuit that includes the at least one hot wire as a resistive element and an extraction circuit that extracts a signal from the bridge circuit indicating the respiratory volume. A first filter and second filter may be disposed at an output side of the extraction circuit, and a detection circuit may be included that detects the respiratory flow rate from the output signal of the first filter and detects sound, such as snoring from the output signal of the second filter.

Abstract: A thermal type flow meter has a first heating resistor, a second heating resistor for blocking heat transfer from the first heating resistor to a console, a temperature measuring resistor interposed between the two heating resistors, and a controller for calculating a flow rate unrelated to temperatures of fluid from temperatures of the resistors and currents supplied to the heating resistors.

Abstract: An artificial sensor comprises at least one substrate, and a plurality of flow sensors disposed on the at least one substrate for providing a plurality of spatial-temporally varying signals representing a hydrodynamic stimulus. The plurality of flow sensors are spatially distributed on the at least one substrate. A processor is coupled to the plurality of flow sensors for receiving the signals and determining spatial-temporal information from the received signals.

Abstract: A sensor having a temperature dependent resistor mounted within a protective housing. The resistor is connected to external circuitry via a pair of connecting wires. In use, variations in temperature of the exhaust gas cause a variation in the temperature experienced by the resistor and consequently, the resistance of the resistor also varies. The resistor is mounted in a projecting end portion of the housing which is of narrower cross-section than the bulk of the housing. The housing is filled with a filler material. The filler material provides support to the resistor and the wires. In the present invention, unlike in prior art sensors, the filler material does not completely fill the housing. Instead a gap is provided which is crossed by the wires. The gap interrupts heat flow through the filler material and thus improves the thermal isolation of the resistor and thereby the accuracy of the sensor. In an alternative embodiment, the sensor additionally comprises an additional heat exchange element.

Abstract: A piping is anchored onto the lower faces of a heater chip and temperature sensor chips by using a thermal conductive adhesive. The heater chip and the temperature sensor chips are coated with a molding resin, and thermal resistance up to an element formed inside thereof is made smallest on a lower face side.

Abstract: There is provided a thermal type flow meter capable of accurately detecting a flow rate even when a fluid temperature varies rapidly or when the fluid temperature is high. A probe includes: a first main heating resistor; a second main heating resistor set at a temperature different from that of the first main heating resistor; and a sub-heating resistor for heating lead wires of the two main heating resistors. A CPU of a sensor control circuit finds a fluid temperature by using the two main heating resistors, and finds a fluid flow rate by using at least one of the two main heating resistors.

Abstract: A low cost, compact, high performance flow sensor that can be made small in size even for use in a large flow rate and a mass flow controller using the same are provided. The flow sensor includes a bypass passage, a sensor passage, and a bridge circuit including heat-generating resistance wires that constitute a part of the bridge circuit and are wound around the sensor passage. The flow sensor determines a total flow rate of a fluid that flows in a branched manner through the bypass passage and the sensor passage at a predetermined flow ratio. The total flow rate is determined by detecting, as an unbalance of the bridge circuit, heat transfer caused by the fluid flowing through the sensor passage and is outputted as a sensor output of the flow sensor. In the flow sensor, the bypass passage includes a plurality of fine flow passages each having a cross-section defined by a substantially linear edge and a curve in contact with the substantially linear edge.

Abstract: A thermal gas-flow measuring instrument has a first heating resistor placed in the gas to be measured. A temperature sensing resistor is positioned upstream or downstream of the first heating resistor and generates signals relating to the flow rate. Between the first heating resistor and the support for supporting the first heating resistor is a second heating resistor that is electrically insulated from the first heating resistor. The second heating resistor suppresses the heat being transferred from the first heating resistor to the support. A control circuit controls the temperatures of the first heating resistor and the second heating resistor so that the operational temperature range of the second heating resistor or the temperature range at the joint section between the first heating resistor and the second heating resistor is at or above the temperature at which water droplets evaporate to disappear by film boiling.

Abstract: A low cost, compact, high performance flow sensor that can be made small in size even for use in a large flow rate and a mass flow controller using the same are provided. The flow sensor includes a bypass passage, a sensor passage, and a bridge circuit including heat-generating resistance wires that constitute a part of the bridge circuit and are wound around the sensor passage. The flow sensor determines a total flow rate of a fluid that flows in a branched manner through the bypass passage and the sensor passage at a predetermined flow ratio. The total flow rate is determined by detecting, as an unbalance of the bridge circuit, heat transfer caused by the fluid flowing through the sensor passage and is outputted as a sensor output of the flow sensor. In the flow sensor, the bypass passage includes a plurality of fine flow passages each having a cross-section defined by a substantially linear edge and a curve in contact with the substantially linear edge.