Abstract: The present disclosure provides an airflow detection circuit, wherein the airflow detection circuit includes: a first thermistor, one terminal of the first thermistor being coupled to a first resistor and a first switch, and the other terminal of the first thermistor being coupled to a first input terminal of a first operational amplifier; a second thermistor, one terminal of the second thermistor being coupled to the first resistor and the first switch, and the other terminal of the second thermistor being coupled to a second input terminal of the first operational amplifier; a voltage source, coupled to the first resistor and the first switch and configured to provide a supply voltage for the first thermistor and the second thermistor through a corresponding supply path based on ON or OFF of the first switch; and a controller, coupled to an output terminal of the first operational amplifier and configured to collect an output signal of the first operational amplifier and determine an airflow flow rate based

Abstract: Systems, methods and computer-readable media are provided for fluid flow measurement in a controlled agricultural environment. A digital flow sensor comprises a flow sensor element including a first digital thermometer for providing a first output and a heating element thermally coupled to the first digital thermometer. The flow sensor may also include a second digital thermometer for providing a second output, and logic for providing a flow measurement based at least in part upon the first and second outputs. A flow sensor network may include multiple digital flow sensors, where data lines of the flow sensors are all coupled to the same network bus for communicating data.

Abstract: A mass flowmeter employing thermal dispersion technology, and method for determining mass flow of a fluid throughout a range beyond that which possible for a constant ?T instrument at increasing power, and below that with which a constant power instrument can provide rapid ?T readings.

Abstract: A thermal flowmeter comprises a heating element thermally coupled to a flowing medium, a first temperature sensor and second temperature sensor. The first temperature sensor detects a flowing medium temperature in a region not affected by the heating element. The second temperature sensor detects a temperature of the heating element and also serves as a heating element. A control unit controls heating power of the heating element based on the difference between the detected temperatures at a predetermined time. The control unit provides a square wave signal to the second temperature sensor so that in a high phase it acts as heating element and in a low phase as a temperature sensor.

Abstract: Systems and methods for detecting a condition of multi-phase flow through a component with a first sensing cable having a first sensor location and aligned with a heating element and a second sensing cable having a second sensing location a predetermined distance from the first sensing location. A heat pulse is propagated through the heating element. A first temperature profile at the first sensing location and a second temperature profile at the second sensing location, each corresponding to the heat pulse, are measured over time. A flow velocity is determined by correlating the first temperature profile with the second temperature profile. A condition of flow of the media is detected by determining a phase of at least one medium exposed to the sensing cable at the first sensing location based on the first temperature profile and the determined flow velocity.

Abstract: A hot wire anemometer circuit has a calibrate subcircuit and an operate subcircuit which are selectively invoked via a user-activate mode switch. The calibrate subcircuit includes a detector configured to compare an amplified sensor voltage with an amplified drive voltage and output an indicator signal when the two voltages match. The drive voltage is derived from a user-adjusted drive resistance of a bridge subcircuit. The operate circuit includes a feedback loop which provides a signal to a bride node of a bridge circuit. After a sensor is connected to the anemometer circuit, the drive resistance is adjusted until the indicator signal is produced, signifying that the circuit is tuned and impedances are matched to prevent oscillations. A slewing network protects the sensor by shorting the drive resistance upon switching the anemometer circuit to the calibrate mode from the operate mode, and gradually restoring the drive resistance when switching back.

Abstract: A flow sensor circuit for a fluid flowpath having a self-heated thermistor situated in a fluid flowpath. The flow sensor circuit is configured to energize the thermistor sufficiently to heat the thermistor, calculate the slope of the leading edge of the rise in temperature of the thermistor when the thermistor is energized, and equate the slope to the state of the fluid flowing through the fluid flowpath. In another embodiment, the flow sensor circuit is configured to energize the thermistor, measure and calculate the average and standard deviation of the thermistor temperature, and determine the state of the flowpath using the thermistor temperature average and standard deviation.

Abstract: In a device and method for measuring a mass flow rate of a fluid, a housing has two hollow pipes communicating with one another and having a fluid inlet and a fluid outlet, an electromagnetic excitation unit excites vibrations in the hollow pipes, two electromagnetic adapters are associated correspondingly with the two pipes and provides signals which are proportional to a speed of vibrations of the pipes of said housing, and an electronic block connected with the electromagnetic excitation unit and with the electromagnetic adapters determines a mass flow rate of a fluid, a correction associated with inclusions in the fluid and constituted by a ratio of a voltage amplitude of the adapters and a voltage amplitude of excitation of vibrations by the electromagnetic excitation unit, and a corrected mass flow rate of the fluid based on the determined mass flow and the determined correction.

Abstract: A water treatment sensor includes a housing having a bottom with an exterior surface in contact with a flow path of a fluid and an interior surface. First and second probes spaced from one another extend from the exterior surface and into the flow path. A first circuit electrically connects the first and second probes and determines a conductivity from a measured resistivity between the probes. First and second temperature sensors are spaced from one another and are coupled to the interior surface. The first sensor determines a temperature of the fluid. A temperature elevated by a heat source and determined by the second sensor is maintained above the temperature of the fluid. A second circuit determines a flow rate of the fluid based on adjustments to the heat source. Communication circuitry communicates the conductivity, the temperature, and the flow rate of the fluid to a controller.

Abstract: An apparatus and method are disclosed for using a thermally active device as a flow meter. The flow meter may have an extremely low mass, rapid response time, and use minimal energy. The flow meter may be located near a flow-side surface of a conduit wall, flush with the surface of a wall, or within a boundary layer of a flow in a conduit. In these locations, the device may present virtually no obstruction to the flow. In certain embodiments, the device may use a resistance temperature device (RTD) heated by a known current, and then tested for resistance at a comparatively much lower (nominally zero) value. A flow rate may be calculated as a function of temperature measurements taken at different steady-state conditions. Flow rates may be so measured at any desired frequency, including very infrequently, such as seconds, minutes, or days apart.

Abstract: A flow meter includes a heater for heating a fluid flow along a membrane. A temperature difference is measured between and upstream point and a downstream point. There are additionally provided one or more strips of material having a relatively high heat conductivity. Strips that are substantially perpendicular to the flow direction direct heat from the heater to the sides of the membrane, causing a large proportion of the heat that would otherwise drive heat flows to be dispersed and decreases inaccuracies or bias in the measured flow rate. Strips of material that are provided parallel to the flow direction act to direct heat from the heater along the direction of flow. This increases the proportion of heat that flows along this axis and guides the flow and hence reduces the proportion of heat available to drive heat flows that cause inaccuracies and bias in the measured flow rates.

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 sensing system that produces a multi-dynamic range output is provided. In an illustrative embodiment, a first channel and a second channel receive an analog output signal from a sensing element. The first channel provides a first digital output signal that has a first dynamic range, and the second channel provides a second digital output signal that has a second narrower dynamic range. In some cases, the second narrower dynamic range falls within the first dynamic range, and the first digital output signal may provide a first resolution and the second digital output signal may provide a second greater resolution. The dynamic range and/or resolution of one or more of the first channel and second channel may be dynamically reconfigurable, if desired.

Abstract: A temperature control system for controlling the rate of flow of a flammable fluid at generally constant pressure is disclosed. The system may include a flow control apparatus that is free of a regulator mechanism, for affecting the flow of the fluid. The flow control apparatus may be operable between at least a first flow rate and a second flow rate, and may have at least one upstream opening and at least one downstream opening. The system may also include a first burner in fluid communication with the downstream opening of the flow control apparatus and a conduit in fluid communication at one end thereof with the upstream opening of the flow control apparatus, and configured at the other end thereof for connection to a fuel supply. A thermocouple may be located in the vicinity of the burner, for converting a sensed thermal state into an electrical signal.

Abstract: An air flow sensor includes a sensor element and a microcontroller, employing a PWM signal to drive the sensor element. Signals from the sensor element are processed by the microcontroller inside the sensor, resulting in continuous readings of air velocity and air temperature.

Abstract: Apparatus and methods of calibrating a microfluidic flow sensor, in which the flow of a fluid through a flow sensor is stopped and a first value is read from the flow sensor, then the fluid is pumped through the flow sensor sequentially at first and second selected rates, and readings from the flow sensor of the flow rate are taken for each of the rates. The readings are used in a polynomial equation to determine the actual flow rate, which is used to calibrate the sensor. The flow sensor can be connected to a computer programmed to perform the calibration method, determine the actual flow rate of the sensor, and make appropriate adjustments to the flow rate of a pump.

Abstract: A flow rate detection method using a heat signal that enables accurate flow rate measurement by eliminating sources of measurement error is provided. The flow rate detection method, using a heat signal, of writing a temperature-change heat signal in a medium traveling through a channel and detecting the heat signal with heat signal detecting means provided at a position away from the writing position, to measure a traveling speed of the medium, wherein first and second temperature sensors 20A and 20B, which are separated by a predetermined distance L, are disposed downstream of the writing position, and the traveling speed is calculated from a time difference at which the two temperature sensors 20A and 20B detecting the heat signal and from the distance L.

Abstract: A fluid property measurement system uses an analog-to-digital converter combined with a multiplexer to measure voltages at one or more points of a measurement circuit and an algorithm within a microcontroller to calculate a fluid property. The measurement circuit has at least one sensor in the fluid stream. The sensor is heated by passing an electric current through the sensor. A second optional upstream sensor is not heated and is at the fluid temperature. The microcontroller then uses the voltage measurements with calibration information and equations based on the desired mode of operation to calculate the fluid property.

Abstract: An air flow sensor includes a sensor element and a microcontroller, employing a PWM signal to drive the sensor element. Signals from the sensor element are processed by the microcontroller inside the sensor, resulting in continuous readings of air velocity and air temperature.

Abstract: A temperature compensating fluid flow sensing system is provided that comprises a resistance-based sensor element that is included in a constant voltage anemometer circuit configured to establish and maintain a command voltage across the first sensor element and to provide a CVA output voltage corresponding to the resistance change in the first sensor element due to heat transfer between the first sensor element and the fluid. A controller is configured to establish the command voltage based on a desired overheat across the sensor and an actual overheat across the first sensor element. A PDR module is configured to determine at least one fluid flow parameter and an actual overheat value based at least in part on the CVA output voltage and to transmit to the controller the actual overheat for use by the controller in updating the command voltage.

Abstract: A system and method are provided to regulate resistance in a discontinuous time hot-wire anemometer. The solution removes supply voltage dependency on the mass airflow output signal. Operating the hot-wire anemometer using discontinuous time regulation offers lower system power, but introduces an inverse supply dependent term in the associated transfer function. This effect is removed by multiplying the output signal via a supply dependent signal.

Abstract: A thermal transient anemometer provides mass flow rate or volume flow rate over smaller discrete regions of a larger flow field, i.e., the distribution of such rates over a predefined, larger area. The thermal transient anemometer comprises two components: a frame with a plurality of sensing cells each having a resistance wire grid and a control unit which includes an energy source which heats the resistance wire grid of each cell, measurement circuitry for determining the decay of resistance of the grid wires as they cool and computational circuitry which determines the mass or volume flow rate through each cell based upon such decay function.

Abstract: A housing for a sensor to prevent condensate from collecting in the sensor. The housing includes a deflector to channel condensate forming in the housing away from the sensor. A notch is provided at the base of the sensor to ensure any condensate forming on the sensor itself does not collect at the sensor base. Further the interior of the housing is roughened and treated with an antifogging agent to ensure any condensate falls continuously so droplets do not form.

Abstract: The present invention relates to a flowmeter suitable for a micro flow sensor. The flowmeter of the present invention comprises a resistive heater to be inserted into a fluid, AC power with a first frequency supplied to the resistive heater to periodically heat the resistive heater, a signal processing unit for detecting a first signal from the resistive heater in relation to a temperature variation of the resistive heater by the AC power, and obtaining a phase lag of the first signal relative to the heat generation in the resistive heater, and an operation unit for calculating a flow rate based on the obtained phage lag. According to the present invention, the flowmeter of the present invention has a wide measurement range and high measurement accuracy with a simple structure.

Abstract: In an air-velocity sensor and a method for operating an air-velocity sensor, the air-velocity sensor includes a temperature sensor arranged in an air flow and sequential electronics. The sequential electronics are used to cyclically impinge upon the temperature sensor with a define heat output and to determine the temperature rise time required by the temperature sensor to heat up to a given temperature difference after being impinged upon with the heat output. Temperature measurements are performed at a defined measuring frequency. The velocity of the air flow is determined on the basis of temperature rise time.

Abstract: A gas flow meter having a gas flow detection circuit for detecting a current flowing through a resistor installed in a gas passage and a voltage generated across the resistor and outputting a voltage signal representing a gas flow passing through the gas passage; a noise reduction circuit for reducing external noise; and a digital adjusting circuit for digitally adjusting a signal representing the detected gas flow and outputting the adjusted signal; wherein a voltage signal based on the signal adjusted by the digital adjusting circuit is output.

Abstract: The spirometer has a low thermal capacity. A circuit supplies power to the spirometer in pulses to heat the spirometer to body temperature. The circuit senses the temperature of the spirometer between intervals. The circuit can also be used in a calorimeter to measure the heat exchange during chemical reactions using the palladium hydrogen. The heating and sensing functions are performed by a single element to result in a small pocket sized device. The portability of the device increases its usefulness.

Abstract: A flowmeter comprising a flow rate detection circuit including a thermal flow rate sensor (10) disposed in a measurement flow passage through which fluid to be measured passes, a temperature sensor circuit (12), a flow rate conversion circuit and a storage means EEPROM. The storage means stores, for respective discrete temperature values, a plurality of individual calibration curves indicating the relationship between electric outputs from the flow rate detection circuit and flow rates, and the individual calibration curves are prepared by using flow rates converted into those at a reference temperature. The flow rate conversion circuit performs interpolation based on temperatures measured by the temperature sensor circuit (12) and a plurality of individual calibration curves to obtain calibrated flow rate values corresponding to temperature at measuring.

Abstract: A heating element (4) is arranged between two temperature sensors (5, 6) in order to measure the mass flow of a liquid or a gas. The mass flow is determined from the temperature difference of the temperature sensors (5, 6). The heating element (4) is operated by pulses in order to reduce power consumption of the device. A further reduction of the power consumption is reached by means of a monitoring circuit (12), which switches the actual measuring section (11) on only if the signals from the temperature sensors (5, 6) fulfil a threshold condition.

Abstract: A calorimetric flow measuring device is characterized by a single thermistor for measuring flow. The thermistor is connected within a bridge circuit which compensates for the temperature of the medium whose flow is being measured and a pulsing heater is provided to periodically heat the thermistor, the rate of cooling of which is a function of the rate of flow. A control devise such as a transistor is connected in the bridge circuit and with the pulsing heater so that temperature compensation is prevented when the heater is activated.

Abstract: The present invention relates to methods and apparatus useful for detecting and measuring flow of a fluid along a flow path. In a method according to the invention, the temperature of a flowing fluid is altered at a selected location for a selected duration so as to generate a pulse in the fluid moving in a downstream direction along a flow path, and the fluid is monitored at a sensing region to detect the pulse passing therethrough. An apparatus according to the present invention may comprise a conduit, a sensor element disposed therein, an energy source proximate to the conduit, and a controller operative to generate an on signal and an off signal respectively operative to activate and deactivate the energy source. The present invention also relates to a liquid chromatography device having a fluid flow detecting and measuring apparatus according to the present invention.

Abstract: A time domain measurement and control system for a hot wire air flow sensor is disclosed in which the air flow sensor is of the type having a resistive heating element with an input end and an output end. The control system includes a fixed frequency variable width pulse generator which generates a pulse train through the heating element. This pulse train, furthermore, has a first predetermined voltage amplitude. The output voltage amplitude of the pulse train is determined at the outlet end of the heating element while a control circuit varies the duty cycle of the pulse train to maintain the output voltage amplitude at a second predetermined voltage level. The duty cycle of the pulse train is proportional to the air flow rate through the air flow sensor.

Abstract: A system and method for measuring flow rate within a fluid-bearing passageway include introducing heat fluctuations into the flow and then non-invasively monitoring the effects of the heat fluctuations propagating to or from one or more interrogation regions. In one embodiment, the non-invasive monitoring detects fluctuations in the refractive index of the flowing fluid as a result of variations in the temperature of the fluid. In another embodiment, electrical conductivity of the fluid is monitored. The heat fluctuations may be introduced using an optical heat generator, such as an infrared laser, or may be introduced using an electrical member, such as a heater coil. Determining the refractive index along the interrogation region may be achieved by monitoring characteristics on an interference pattern, but other optical arrangements may be utilized.

Abstract: A thermal-type flowmeter for detecting a flow rate of a fluid such as intake air flow rate in an internal combustion engine includes a voltage converting circuit for converting a flow-rate indicating voltage signal outputted from a flow-rate detecting sensor element into a voltage of a level falling within a predetermined range, a voltage-to-current converting circuit for converting the voltage into a current of magnitude which is proportional to a value of the flow-rate indicating voltage signal, a current-to-voltage converting circuit for converting the current mentioned above into a voltage signal for analogue-to-digital conversion, and a voltage adjusting circuit for increasing or decreasing the output voltage level of the voltage converting circuit in dependence on the value of the flow-rate indicating voltage signal. The voltage of a current source for the voltage-to-current converting circuit can be regulated so as to conform with the input voltage.

Abstract: A thermal pulsed micro flow sensor includes thermal sensors positioned in a fluid channel at downstream positions relative to a heater. Flow rate is measured by determining the time that it takes a thermal pulse to pass between two of the sensors. Since the resolution of the measurement increases with increasing distance between sensors while the accuracy of the measurement decreases, there is a conflict between the requirements of accuracy and short response time, as well as between accuracy and resolution. By providing at least three sensors and by varying the distances between the sensors, however, it is possible to select a pair of sensors having the highest resolution required by the application in which the sensor is used, while still ensuring that the velocity measurement is within the range of velocities accurately measurable by the selected sensors.

Abstract: Disclosed is a thermal flow meter which is relatively inexpensive and operates with high accuracy and reliability, and a fuel controller using the thermal flow meter adapted for internal combustion engines. The thermal flow meter comprises a sensor unit for detecting a flow rate signal, a reference power supply for generating a reference signal, and a signal switch for selectively outputting the flow rate signal from the sensor unit and the reference signal from the reference power supply. The flow rate signal and the reference signal are alternately output from the same output terminal.

Abstract: A digital-to-analog converter 41, capable of setting a voltage V41 of an offset value using information JS. At the time of an offset correction operation, the voltage V41 of the offset signal is sequentially varied to automatically set it to a value that is extremely close to a lower executable conversion limit Vbottom within the convertible range of the analog-to-digital converter. With this structure it is possible to provide a sensor circuit that is capable of preventing lowered precision with temperature variations.