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WO1992010725A1 - Anemometre a resistance electrique - Google Patents

Anemometre a resistance electrique Download PDF

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Publication number
WO1992010725A1
WO1992010725A1 PCT/GB1991/002191 GB9102191W WO9210725A1 WO 1992010725 A1 WO1992010725 A1 WO 1992010725A1 GB 9102191 W GB9102191 W GB 9102191W WO 9210725 A1 WO9210725 A1 WO 9210725A1
Authority
WO
WIPO (PCT)
Prior art keywords
hot wire
wire anemometer
sensor
anemometer according
gas
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Ceased
Application number
PCT/GB1991/002191
Other languages
English (en)
Inventor
Peter Wall
Anthony Thomas
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Abbey Biosystems Ltd
Original Assignee
Abbey Biosystems Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority claimed from GB909026860A external-priority patent/GB9026860D0/en
Application filed by Abbey Biosystems Ltd filed Critical Abbey Biosystems Ltd
Publication of WO1992010725A1 publication Critical patent/WO1992010725A1/fr
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

Links

Classifications

    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B5/00—Measuring for diagnostic purposes; Identification of persons
    • A61B5/08—Measuring devices for evaluating the respiratory organs
    • A61B5/087—Measuring breath flow
    • A61B5/0878—Measuring breath flow using temperature sensing means
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01F—MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
    • G01F1/00—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow
    • G01F1/704—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow using marked regions or existing inhomogeneities within the fluid stream, e.g. statistically occurring variations in a fluid parameter
    • G01F1/708—Measuring the time taken to traverse a fixed distance
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01F—MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
    • G01F1/00—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow
    • G01F1/704—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow using marked regions or existing inhomogeneities within the fluid stream, e.g. statistically occurring variations in a fluid parameter
    • G01F1/708—Measuring the time taken to traverse a fixed distance
    • G01F1/7084—Measuring the time taken to traverse a fixed distance using thermal detecting arrangements
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01P—MEASURING LINEAR OR ANGULAR SPEED, ACCELERATION, DECELERATION, OR SHOCK; INDICATING PRESENCE, ABSENCE, OR DIRECTION, OF MOVEMENT
    • G01P5/00—Measuring speed of fluids, e.g. of air stream; Measuring speed of bodies relative to fluids, e.g. of ship, of aircraft
    • G01P5/18—Measuring speed of fluids, e.g. of air stream; Measuring speed of bodies relative to fluids, e.g. of ship, of aircraft by measuring the time taken to traverse a fixed distance

Definitions

  • This invention relates to hot wire anemometers suitable for measurements of gas flow in clinical applications. More specifically the present invention relates to a pulsed hot wire anemometer which may act as a time of flight sensor.
  • All such devices have to be able to respond accurately and rapidly over a wide range of dynamically changing flow rates. They must not impede the patient's breathing ability and the requirements of a device for use with adults are different to those for use with infants and neonates.
  • the "dead space" of the sensors used must be as small as possible.
  • the devices should, ideally, be capable of differentiating between inhalation and exhalation cycles.
  • the response characteristics of these devices should be independent of gas temperature, gas density/composition, humidity and viscosity.
  • Hot wire anemometry exploits the cooling effect of air moving over a heated resistance element (usually a fine wire suspended in the gas flow). Since the rate of heat loss from the heated element will be directly influenced by the velocity of any gas moving past it, this can be used to determine the gas velocity. However, this is not independent of gas composition since the heat capacity and density of the gas have significant effects. Pulsing the heating element can remove the density dependence and enable true "time of flight" measurements to be made.
  • GB 2210983 describes an anemometer with a pulsed heating element.
  • the anemometer described comprises at least two transmitting wires and at least two sensor wires (all of which are fixed in the flow of the fluid), means for supplying heat to the pulsed wire, means for detecting and monitoring the heat pulse arriving at the sensor wire, means for measuring the interval between successive pulses, and means for measuring the interval between initiation of the pulse and detection of the pulse at the sensor wire.
  • the sensor chamber comprises an inlet for gas, an outlet for gas, and, intermediate between said inlet and said outlet, a single elongate resistance element and two elongate sensor elements, all said elements being fixed in a common plane parallel to gas flow, said resistance element being intermediate between said sensor elements.
  • the anemometer preferably comprises means for initiating a heat pulse in the resistance element, means for detecting and monitoring a heat pulse arriving at each sensor element, means for measuring the interval between successive pulses, and means for measuring the interval between initiating the pulse and detecting the pulse at the respective sensor element.
  • the resistance element and the sensor elements are preferably located symmetrically in the sensor chamber, which has an inlet/outlet for gases at each end thereof.
  • the resistance element is spaced about 1mm from each of the respective sensor elements, and is generally parallel thereto.
  • the sensor elements are typically about 5 microns in diameter and composed of tungsten coated with gold; platinum can alternatively be used.
  • the sensor elements are preferably connected in a balanced bridge circuit.
  • the resistance element is preferably of a noble metal. In this case platinum is preferred; iridium is an alternative.
  • the diameter of the resistance element is typically about 20 microns.
  • a smooth plate may, in some embodiments be placed substantially parallel to the direction of flow and to the sensor elements, so that the respective sensor element will be in the boundary layer of the plate, where the flow will be more laminar. There are generally meshes at either end of the sensor chamber to make the flow pattern inside the sensor chamber substantially independent of the geometry of the connecting tubing, which also produces a more even flow.
  • the sensor chamber has a casing of a gamma radiation sterilisable polymer, such as polystyrene.
  • Figure 1 is an illustrative schematic plan view of a sensor chamber employed in an anemometer according to the invention
  • FIG. 2 is an illustrative block diagram of electronic circuitry suitable for use with an anemometer according to the invention.
  • Figure 3 is a diagram showing individual components of the sensor chamber and the lines over which they are connected to the circuit of Figure 2.
  • the sensor chamber 1 comprises a resistance wire 2, sensor wire 3, and a further sensor wire 4.
  • a cylinder of heated gas is formed around the resistance wire
  • wire 3 functions as a receiver and wire 4 as reference. As the gas flow carries heated gas towards wire 3, the temperature of wire
  • wire 3 acting as the reference and wire 4 acting as the receiving element.
  • Sensor wire 4 is thus heated by gas flown past the resistance wire 2, increasing its electrical resistance compared to that of wire 3.
  • the resistance bridge imbalance between the two wires is the inversion of that caused by gas flow in the opposite direction.
  • the direction of the gas flow can thus be determined, enabling respiratory exhalation and inhalation cycles to be differentiated.
  • the cylinder of hot gas produced around the resistance element will diffuse outwards towards wires 3 and 4, and will reach both wires at the same time, causing no disturbance in the resistance bridge.
  • the resistance wire When the heating pulse is initiated (typically for about 10 microseconds), the resistance wire may reach a temperature of about 200°C.
  • the temperature of gases entering the sensor chamber is generally between 35 and 38°C and the gases have a high water vapour content. Condensation of water vapour onto the surfaces of the sensor chamber or wire elements would impair the sensor function and produce erroneous gas flow measurements.
  • the whole of the chamber is generally heated to about 40°C.
  • the sensor is preferably calibrated for flow rates in each direction; separate potentiometers are generally employed for each direction of flow.
  • the tension in the wires is critical in ensuring that the accuracy and full dynamic range of the sensor is maintained.
  • the wires may be fixed in place by the use of microresistance welding or laser spot welding or similar techniques. Conductive adhesives may not ensure that constant tension is maintained and are therefore generally unsuitable.
  • the illustrated anemometer contains a sensor chamber 1 (as described above with reference to Figure 1), a signal generating and conditioning circuit 5 provided with a power supply 6 (which supplies a.c. across transformer 7) and an interface and video circuit 8.
  • Circuit 8 drives various utilities such as display cathode ray tube 16, a chart recorder (analog) output 17 and a serial output 18; the circuit is provided with a keyboard input 19 under the control of an instrument control microprocessor 11.
  • Circuit 5 is arranged to transmit pulses over line 12 to resistance wire 2 in the sensor chamber 1, to receive over line 13 output signals from the bridge in which the wires 3 and 4 are connected, to provide heater control signals over line 14, and to receive calibration signals over line 15.
  • resistance wire 2 is connected between line 12 and ground.
  • the bridge which includes wires 3 and 4 is connected between a supply rail + V and ground and has its output comers connected to the inputs of a differential amplifier driving line 13.
  • a heater coil H is connected between line 14 and ground and provides the background heating within the chamber: the actual temperature is sensed by thermistor TH which is connected between ground and line 14 and the signal on line 14 is used for thermostatic control.
  • One or more calibration potentiometers are connected between ground and line 15.
  • Circuit 5 is further connected to a flight time measurement and sampling rate generator 20, which provides two timers for respectively, measuring the flight time and generating sampling rate (i.e. transmit pulses 12). These two parameters are passed to the sensor control microprocessor 21 for calculating flow-rate and the. volume.
  • the flow-rate is calculated from:
  • a breath is registered when the flow changes from negative direction (expiration) to a positive flow (inspiration). To reduce the effect of spurious breath if the breath volume is below a certain level (say 0.1 ml or 10% of the average tidal volume) it is rejected.
  • Signals corresponding to above parameters and the state of the sensor are passed through the isolation barrier 9 (typically in the form of an opto isolator 10) to the interface and video circuits 8.

Landscapes

  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Health & Medical Sciences (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Fluid Mechanics (AREA)
  • Engineering & Computer Science (AREA)
  • Pathology (AREA)
  • Medical Informatics (AREA)
  • Physiology (AREA)
  • Biophysics (AREA)
  • Aviation & Aerospace Engineering (AREA)
  • Biomedical Technology (AREA)
  • Heart & Thoracic Surgery (AREA)
  • Pulmonology (AREA)
  • Molecular Biology (AREA)
  • Surgery (AREA)
  • Animal Behavior & Ethology (AREA)
  • General Health & Medical Sciences (AREA)
  • Public Health (AREA)
  • Veterinary Medicine (AREA)
  • Measuring Volume Flow (AREA)

Abstract

Anémomètre à résistance électrique permettant de mesurer l'écoulement d'un gaz dans des applications cliniques, comprenant une chambre de détection (1) comportant des orifices d'entrée et de sortie pour le gaz. Entre les orifices d'entrée et de sortie pour le gaz, on a prévu une paire d'éléments de capteurs allongés et espacés (4, 3) et une résistance allongée intermédiaire (2), tous ces éléments étant fixés sur le même plan parallèlement au sens d'écoulement du gaz A. De manière spécifique, la résistance allongée est placée pour émettre des impulsions de chaleur permettant de déterminer le 'temps de vol' du gaz chauffé pour atteindre un élément de capteur. .
PCT/GB1991/002191 1990-12-11 1991-12-10 Anemometre a resistance electrique Ceased WO1992010725A1 (fr)

Applications Claiming Priority (4)

Application Number Priority Date Filing Date Title
GB9026860.8 1990-12-11
GB909026860A GB9026860D0 (en) 1990-12-11 1990-12-11 Gas flow meter for clinical use
GB9106567.2 1991-03-27
GB919106567A GB9106567D0 (en) 1990-12-11 1991-03-27 Hot wire anemometer

Publications (1)

Publication Number Publication Date
WO1992010725A1 true WO1992010725A1 (fr) 1992-06-25

Family

ID=26298090

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/GB1991/002191 Ceased WO1992010725A1 (fr) 1990-12-11 1991-12-10 Anemometre a resistance electrique

Country Status (2)

Country Link
EP (1) EP0513309A1 (fr)
WO (1) WO1992010725A1 (fr)

Cited By (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2697911A1 (fr) * 1992-11-10 1994-05-13 Schlumberger Ind Sa Débitmètre volumique à mesure de temps de vol.
DE10246683A1 (de) * 2002-10-07 2004-04-15 Gottlieb Weinmann - Geräte für Medizin und Arbeitsschutz - GmbH + Co. Vorrichtung zur Messung von fluidischen Strömungen
EP2268189A1 (fr) * 2008-05-01 2011-01-05 Spiration, Inc. Systèmes, procédés et appareils de capteurs pulmonaires directs
US8926647B2 (en) 2002-03-20 2015-01-06 Spiration, Inc. Removable anchored lung volume reduction devices and methods
US8956319B2 (en) 2002-05-17 2015-02-17 Spiration, Inc. One-way valve devices for anchored implantation in a lung
US8974527B2 (en) 2003-08-08 2015-03-10 Spiration, Inc. Bronchoscopic repair of air leaks in a lung
US8974484B2 (en) 2001-09-11 2015-03-10 Spiration, Inc. Removable lung reduction devices, systems, and methods
US8986336B2 (en) 2001-10-25 2015-03-24 Spiration, Inc. Apparatus and method for deployment of a bronchial obstruction device
US9198669B2 (en) 2006-03-31 2015-12-01 Spiration, Inc. Articulable anchor

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3962917A (en) * 1974-07-03 1976-06-15 Minato Medical Science Co., Ltd. Respirometer having thermosensitive elements on both sides of a hot wire
US4114608A (en) * 1976-02-11 1978-09-19 Chesebrough-Pond's Inc. Inhalation device
US4483200A (en) * 1981-01-19 1984-11-20 Anima Corporation Thermal pulse flowmeter
EP0173461A1 (fr) * 1984-08-29 1986-03-05 General Motors Corporation Débitmètre de fluide à diffusion thermique
EP0314325A1 (fr) * 1987-10-08 1989-05-03 Btg International Limited Débitmètre à gaz pour usage chimique

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3962917A (en) * 1974-07-03 1976-06-15 Minato Medical Science Co., Ltd. Respirometer having thermosensitive elements on both sides of a hot wire
US4114608A (en) * 1976-02-11 1978-09-19 Chesebrough-Pond's Inc. Inhalation device
US4483200A (en) * 1981-01-19 1984-11-20 Anima Corporation Thermal pulse flowmeter
EP0173461A1 (fr) * 1984-08-29 1986-03-05 General Motors Corporation Débitmètre de fluide à diffusion thermique
EP0314325A1 (fr) * 1987-10-08 1989-05-03 Btg International Limited Débitmètre à gaz pour usage chimique

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
ISA Transactions page 69-78, Vol. 21, No. 1, 1982 J. K. Eaton et al: "Two New Instruments for Flow Direction and Skin-Friction Measurements in Separated Flows ", *

Cited By (12)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2697911A1 (fr) * 1992-11-10 1994-05-13 Schlumberger Ind Sa Débitmètre volumique à mesure de temps de vol.
EP0597530A1 (fr) * 1992-11-10 1994-05-18 Schlumberger Industries S.A. Débitmètre volumique à mesure de temps de vol
US5335555A (en) * 1992-11-10 1994-08-09 Schlumberger Industries S.A. Volume flow meter that measures transit time
US8974484B2 (en) 2001-09-11 2015-03-10 Spiration, Inc. Removable lung reduction devices, systems, and methods
US8986336B2 (en) 2001-10-25 2015-03-24 Spiration, Inc. Apparatus and method for deployment of a bronchial obstruction device
US8926647B2 (en) 2002-03-20 2015-01-06 Spiration, Inc. Removable anchored lung volume reduction devices and methods
US8956319B2 (en) 2002-05-17 2015-02-17 Spiration, Inc. One-way valve devices for anchored implantation in a lung
DE10246683A1 (de) * 2002-10-07 2004-04-15 Gottlieb Weinmann - Geräte für Medizin und Arbeitsschutz - GmbH + Co. Vorrichtung zur Messung von fluidischen Strömungen
US8974527B2 (en) 2003-08-08 2015-03-10 Spiration, Inc. Bronchoscopic repair of air leaks in a lung
US9622752B2 (en) 2003-08-08 2017-04-18 Spiration, Inc. Bronchoscopic repair of air leaks in a lung
US9198669B2 (en) 2006-03-31 2015-12-01 Spiration, Inc. Articulable anchor
EP2268189A1 (fr) * 2008-05-01 2011-01-05 Spiration, Inc. Systèmes, procédés et appareils de capteurs pulmonaires directs

Also Published As

Publication number Publication date
EP0513309A1 (fr) 1992-11-19

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