Abstract: The flow amount measuring apparatus has two detecting portions for generating signal indicative of flow amount respectively. The outputs of two detecting portions are subject to a differential amplification to obtain large output signal and low amplitude ratio. A plurality of resistors providing the detecting portion may be formed on a single substrate. The output characteristic of the flow amount measuring apparatus can be adjusted by adjusting the gain and the offset. The offset includes a temperature dependent first offset component and a constant second offset component. The first offset component varies in accordance with temperature of fluid so as to reduce temperature dependency of the output characteristic. As a result, it is possible to measure flow amount accurately.

Abstract: A thermal air flow rate measuring apparatus of great precision is disclosed. In the thermal air flow rate measuring apparatus, sensitivity is enhanced by sensors having different output characteristics and an operating means employing a digitized signal, and the sensitivity and temperature can be corrected easily depending on the flow direction of fluid.

Abstract: A thermal type flow measuring device comprises a heating resistor(HF), a temperature measuring resistor(Ru) upstream of the heating resistor(HF) with respect to a fluid(Q), and a temperature measuring resistor(Rd) downstream of the heating resistor(HF). A heat sensitive resistance element(CF), the upstream temperature measuring resistor(Ru) and the downstream temperature measuring resistor(Rd) form a first bridge circuit, and this first bridge circuit and the heating resistor(HF) form a second bridge circuit. Feedback control means(OP1, Tr) heat the heating resistor(HF) in accordance with an output for keeping a balance of the second bridge circuit.

Abstract: An apparatus for measuring a gas flow rate, which includes one or more resistors arranged in a gas passage, and a gas flow rate detection circuit for outputting a gas flow rate detection signal in accordance with a gas flow rate by detecting currents flowing through the resistors or voltages generated in accordance with the currents. The apparatus includes a fixed resistor connected in series to one of the resistors, and a first A/D converter circuit for converting an input voltage into a digital signal based on a reference voltage and outputting the digital signal by using a voltage generated in the fixed resistor as the reference voltage and using a voltage generated in a combined resistance of the resistor and the fixed resistor as the input voltage, wherein a digital output signal of a gas temperature detection signal is obtained by the first A/D converter circuit.

Abstract: A flow rate signal analog-digital conversion circuit 30, an adjustment processing circuit 40 and a chip temperature sensor circuit 60 are disposed a single semiconductor chip 100 to form an integrated circuit, and a chip temperature signal in a form of digital signal outputted from the chip temperature sensor circuit 60 is inputted into the adjustment processing circuit 40 in which correction reducing temperature dependent error in a series of signal processing circuits is performed. Thereby, a board temperature dependent error in a gas flow rate measuring device can be reduced in which adjustment is performed for digital signals.

Abstract: An air flow sensor including a temperature dependent resistor device, a first circuit and a second circuit. The first circuit applies a voltage to the temperature dependent resistor device until it reaches a first temperature. The first circuit includes a first reference resistance leg, a first variable resistance leg including the temperature dependent resistor device, and a first comparator connected to both legs for determining when the temperature dependent resistor device reaches the first temperature. The second circuit includes a second reference resistance leg, a second variable resistance leg including the temperature dependent resistor device, and a second comparator connected to both legs for determining when the temperature dependent resistor device reaches a second temperature.

Abstract: A hot-wire type air flow meter for an internal combustion engine has an exothermic resistor film provided on a thin portion formed on a silicon substrate and a control circuit for controlling a voltage to be applied to the resistor film or a current to be supplied. The resistor film is arranged in a suction pipe of the internal combustion engine and heat is emitted to an air through the resistor film. In the case where a liquid droplet is deposited onto the resistor film, the control circuit controls the applied voltage to a value smaller than a voltage which is applied to the resistor film at the time of measuring a maximum specified measuring range or controls the supply current to a value smaller than a current flowing in the resistor film at the time of measuring the maximum specified measuring range.

Abstract: A thermal type flow rate detector includes: a bridge circuit constructed by upstream side and downstream side temperature detecting elements for detecting a temperature of fluid flowing from the upstream side to the downstream side, and fixed resistors; and a temperature difference controlling circuit for continuously supplying an electric power to upstream side and downstream side heat generating elements so that a temperature difference between the temperature detecting elements becomes a predetermined value. The temperature difference controlling circuit includes: a differential amplifier connected to the bridge circuit; a first constant voltage power supply; a second constant voltage power supply having a lower constant voltage than that of the first constant voltage power supply; and the upstream side and downstream side heat generating elements.

Abstract: A bidirectional flow sensor (800) for automated systems includes a heater (18) which is maintained at a constant temperature above the temperature of the fluid flowing past the heater. A pair of temperature sensors (26a,26b) is located to either side of the heater (18). The temperature sensors may be two-terminal constant-current devices, electrically connected in series, so that the current is controlled by the sensor sensing the lower temperature, which is on the upstream side of the heater. In one embodiment, a processor (1010) processes the signals produced by the temperature sensors to produce a flow-direction indicating signal. The bidirectional sensor is adapted for interfacing with a digital network.

Abstract: To offer a mass airflow measuring apparatus in which the effect of the adhesion onto the heating resistor caused while the engine is off is reduced and the measuring accuracy is improved. The apparatus measures the mass airflow of the air sucked into the internal combustion engine, using the heating resistor 1. The power control circuit 4 maintains the heating resistor 1 temperature equal to or higher than the temperature during the operation of the internal combustion engine after the internal combustion engine has stopped and until the temperature of the internal combustion engine and its apparatuses installed in the suction system has lowered below the generation temperature of volatile gas such as oil vapor.

Abstract: A gas mass flow sensor or probe (35, 37, 39) of an air flow sensing and control system (17, 19, 21) based upon hot-wire type devices where flow sensing is achieved by controlling the difference between two temperature sensing elements (51 and 53) suspended in the flow stream (41, 43, 45). The first element (53) is used to measure the ambient temperature of the fluid flow and the second element (51) is maintained at a programmed temperature (121) above ambient by a current-fed heater (49). The mass flow rate density is determined from heater current (117) required to maintain the temperature difference and the total flow in the duct is inferred. To measure the flow in which the elements (51, 53) are submerged, electronic circuitry monitors the two temperature elements (51, 53) and controls the amount of current through the heater (49) such that there will always be a predetermined difference between the ambient and heated temperatures. The sensor provides an output signal (101) for use by other devices (23).

Abstract: An apparatus for measuring a gas flow rate, which includes one or more resistors arranged in a gas passage, and a gas flow rate detection circuit for outputting a gas flow rate detection signal in accordance with a gas flow rate by detecting currents flowing through the resistors or voltages generated in accordance with the currents. The apparatus includes a fixed resistor connected in series to one of the resistors, and a first A/D converter circuit for converting an input voltage into a digital signal based on a reference voltage and outputting the digital signal by using a voltage generated in the fixed resistor as the reference voltage and using a voltage generated in a combined resistance of the resistor and the fixed resistor as the input voltage, wherein a digital output signal of a gas temperature detection signal is obtained by the first A/D converter circuit.

Abstract: An improved mass flow sensor interface (“MFSI”) circuit and method are disclosed for sensing and measuring mass flow rate of a gas and provide an output voltage proportional to the mass flow rate in a mass flow controller. The improved MFSI circuit of the present invention includes upstream and downstream mass flow sense elements a precision current source to drive the circuit. The circuit further includes an operational amplifier to sum the voltage upstream of the upstream sense element with the voltage downstream of the downstream sense element. A reference voltage is electrically connected to the positive node of the operational amplifier. An upstream shunting resistor and a downstream shunting resistor share a common junction at the negative node of the operational amplifier and are electrically connected in parallel to the upstream and downstream mass flow sense elements.

Abstract: A flow rate signal analog-digital conversion circuit 30, an adjustment processing circuit 40 and a chip temperature sensor circuit 60 are disposed a single semiconductor chip 100 to form an integrated circuit, and a chip temperature signal in a form of digital signal outputted from the chip temperature sensor circuit 60 is inputted into the adjustment processing circuit 40 in which correction reducing temperature dependent error in a series of signal processing circuits is performed. Thereby, a board temperature dependent error in a gas flow rate measuring device can be reduced in which adjustment is performed for digital signals.

Abstract: An air flow detection apparatus useful in operating an accessory item in an HVAC system includes a sensor printed circuit board assembly having a first thermistor adapted to be exposed to an air flow and associated with a first pair of heating resistors. A second thermistor is placed in parallel with the first thermistor and is adapted to be hidden from the air flow and is associated with a second pair of heating resistors. A control printed circuit board assembly is interconnected with the sensor printed circuit board assembly and has a voltage regulator circuit for applying a DC voltage source to a power regulator circuit and a sensor monitoring circuit interfaced therewith.

Abstract: A sensor that includes a first resistor, a second resistor, a first circuit, and a second circuit. The first and second resistors each has a resistance that varies in response to a change in a physical property. The first circuit is electrically coupled to the first resistor and sets the resistance of the first resistor. The second circuit is electrically coupled to the second resistor and adjusts the resistance of the second resistor to equal the resistance of the first resistor. A processing circuit may be coupled to the first and second circuits to measure a difference in an amount of energy provided by the first and second circuits to the first and second resistors, respectively.

Abstract: The invention provides a flow rate detector capable of precisely detecting a flow rate of an object fluid and effectively reducing a leaning error even when the object fluid is pulsating, thereby improving precision in detection of flow rate. The flow rate detector comprises a flow detector 50 for outputting a flow-detecting signal Sf according to a flow rate of the object fluid utilizing heat transfer phenomenon from an exothermic resistor 12 disposed in a fluid passage to the object fluid, and a gain compensator 60 for compensating an error in a flow-detecting signal Sf by amplifying the flow-detecting signal Sf from the flow detector 50, wherein the gain compensator 60 is arranged to amplify the flow-detecting signal Sf by a substantially constant alternating current gain G3 larger than a direct current gain G1 at the time of zero frequency, in a frequency range higher than a frequency f2A corresponding to the minimum pulsating frequency of the object fluid.

Abstract: A bi-directional mass air flow sensing device for measuring air flow, comprising a bridge circuit coupled across a voltage potential, wherein the bridge circuit comprises a first side including first and second temperature dependent sensor resistors connected in series and disposed on a thermally insulative substrate window in line with an air flow and arranged such that relative to a first direction of air flow, the first sensor resistor is upstream of the second sensor resistor, and a second side in parallel with the first side and including third and fourth temperature dependent sensor resistors connected in series and disposed on the thermally insulative substrate in line with the air flow such that relative to the first direction of air flow, the third sensor resistor is upstream of the fourth sensor resistor, and a temperature dependent balance resistor connected between the first and second temperature dependent sensor resistors on the first side of the bridge circuit.

Abstract: The invention provides a flow rate detector capable of precisely detecting a flow rate of an object fluid and effectively reducing a leaning error even when the object fluid is pulsating, thereby improving precision in detection of flow rate. The flow rate detector comprises a flow detector 50 for outputting a flow-detecting signal Sf according to a flow rate of the object fluid utilizing heat transfer phenomenon from an exothermic resistor 12 disposed in a fluid passage to the object fluid, and a gain compensator 60 for compensating an error in a flow-detecting signal Sf by amplifying the flow-detecting signal Sf from the flow detector 50, wherein the gain compensator 60 is arranged to amplify the flow-detecting signal Sf by a substantially constant alternating current gain G3 larger than a direct current gain G1 at the time of zero frequency, in a frequency range higher than a frequency f2A corresponding to the minimum pulsating frequency of the object fluid.

Abstract: An integrated sensor for automated systems includes a flow sensor, a temperature sensor, and a network interface. In a particular embodiment of the invention, the flow sensor includes a temperature sensor (26) which determines the temperature of the fluid flowing in a flow path (12). A heater (18) is coupled to the flow path, and is energized by a controller (20) with sufficient electrical power to raise the temperature of the heater above the measured fluid temperature by a fixed temperature difference. In order to aid in determining the temperature difference, a sensor (24) may be associated with the heater (18). The amount of power required to maintain the temperature difference is a measure of the flow velocity. The volumetric flow rate is the product of the flow velocity multiplied by the area of the flow sensor. The mass flow rate is the product of the volumetric flow rate multiplied by the mass density of the fluid.

Abstract: A hot wire gas flow rate sensor having a bridge circuit with a sensing resistor avoids saturation of the signal processing circuitry at high gas flow rates by increasing a bias signal to a differential amplifier in the signal processing circuitry in a step-like manner as the flow rate responsive signal to the differential amplifier from the sensing resistor increases. The differential input signal to the amplifier is thus maintained at a level that avoids saturation of the amplifier. Appropriate scaling is provided to the output circuitry of the sensor in accordance with changes in the bias signal so that the sensor output correctly indicates gas flow rates. Compensation is provided for changes in gas composition and when the sensing resistor is changed by determining the voltage drop across a first sensing resistor with a gas of known composition at a zero gas flow condition. The voltage drop across a second sensing resistor at the zero gas flow condition for the gas is also determined.

Abstract: A temperature regulator, circuit for an air-mass flow meter in which the temperature regulator circuit includes a bridge circuit one of whose bridge branches contains a temperature resistor of substantially higher resistance than a heating resistor in the other bridge branch. The resistance element of the temperature resistor normally requires a large amount of space on the sensor for this purpose. In order to reduce the size of the resistance element, a voltage divider is provided to reduce the input voltage applied to the temperature resistor. In order to maintain the bridge balance, additional circuit elements are provided in the other bridge branch containing the heating resistor.

Abstract: The invention relates to a device for measuring the flaw of a medium, e.g., a gaseous medium or a fluid medium, which device is based on measuring and affecting the temperature distribution of a medium flowing along, which flow sensor comprises two objects, each comprising a heating element and a temperature sensor, the measured temperature difference being kept, by way of a control loop, to the value of zero, the asymmetry of the power supply to the objects in order to comply with the aforesaid criterion, according to which the temperature difference must be zero, being representative of the value to be measured of the medium flow, taking into account parameters associated with the medium, such as its density and specific heat.

Abstract: The invention relates to a device for measuring the flow of a medium e.g., a gaseous medium or a fluid medium, which device is based on measuring and affecting the temperature distribution of a medium flowing along, which flow sensor comprises two object, each comprising a heating element and a temperature sensor, the measured temperature difference being kept, by way of a control loop, to the value of zero, the asymmetry of the power supply to the objects in order to comply with the aforesaid criterion, according to which the temperature difference must be zero, being representative of the value to be measured of the medium flow, taking into account parameters associated with the medium, such as its density and specific heat.

Abstract: A thermal type air flow sensor which corrects variation of characteristics of a thermal type air flow sensor due to adherence or deposition of fouling contained in an intake air for maintaining an initial accuracy. An air flow rate is measured by means of a heating resistor and a temperature measuring resistor formed by semiconductor fine patterning. A part of the semiconductor substrate is removed. The heating resistor and a portion of the temperature measuring resistor are formed above a space defined by removing the semiconductor substrate. A voltage of the portion of the temperature measuring resistor located above the space is detected for correcting an error in measurement of an intake air using the voltage detected.

Abstract: A sensor that includes a first resistor, a second resistor, a first circuit, and a second circuit. The first and second resistors each has a resistance that varies in response to a change in a physical property. The first circuit is electrically coupled to the first resistor and sets the resistance of the first resistor. The second circuit is electrically coupled to the second resistor and adjusts the resistance of the second resistor to equal the resistance of the first resistor. A processing circuit may be coupled to the first and second circuits to measure a difference in an amount of energy provided by the first and second circuits to the first and second resistors, respectively.

Abstract: An improved heating resistor type air flow measurement apparatus which can operate properly even when the noises are produced by a large surge current, and even when the air flow measurement apparatus is made of plastic member. The apparatus has a heating resistor arranged in the main air passage, a temperature-sensitive resistor and a flow measurement circuit for processing signals from their resistors. Inductors are provided between these resistors to prevent noise invasion into the flow measurement circuit.

Abstract: Thermal dispersion probes used as flowrate sensors in process control of a medium heated by a heater. The device includes a reference temperature sensor for producing an electrical signal indicative of the temperature of the medium in which it is immersed, and an active temperature sensor for producing an electrical signal indicative of the temperature of the medium adjacent the heater. The temperature difference between the active sensor and the reference sensor is processed in a processor which varies the heater power to maintain the temperature differential between the active sensor and the reference sensor within a predetermined range, whereby the predetermined range provides an optimal sensitivity for the probes.

Abstract: A heat sensitive flow meter comprising a power source for changing an offset voltage &Dgr;E at the time of application of a power voltage. The power source is connected to the non-inversion input terminal of an operation amplifier for amplifying a potential difference between a first heat sensitive element for measuring the temperature of a fluid and a second heat sensitive element which is cooled by the fluid. The heat sensitive flow meter can suppress an output error right after the application of a power voltage and shorten a target signal reach time.

Abstract: A flow rate sensor comprises: a main fluid passage for a fluid to flow therealong; a detecting pipe conduit coaxially disposed in the main fluid passage; a temperature sensing element for sensing the temperature of the fluid; a flow rate sensing element including a flow rate detecting resistance made of a thermo-sensitive electrically resistant material, the flow rate detecting element being disposed in the main fluid passage in a manner such that the flow rate detecting resistance is exposed to the fluid flowing therethrough; and a control circuit for controlling an electric current flowing to the flow rate detecting resistance such that the temperature of the flow rate detecting resistance may be maintained at a predetermined value which is higher to some extent than a fluid temperature detected by the temperature sensing element. The main fluid passage involves a converged section whose passage cross sectional area becomes gradually smaller towards the downstream side thereof.

Abstract: A method and apparatus for determining selected fluid properties using a self-oscillating fluid sensor. In a preferred embodiment, a sensor is provided that oscillates at a frequency that is related to the transit time of a temperature disturbance through the fluid. Based on the transit time, selected fluid properties of the fluid can be determined.

Abstract: A heat-sensitive type flow sensor which can be manufactured by using discrete parts at low cost in a miniature size with high accuracy and reliability includes a correcting circuitry capable of compensating for a detected current indicating a flow rate of a fluid of concern and outputted from a flow rate detecting circuit.