EP0108141A1 - Analyseur d'oxygene - Google Patents

Analyseur d'oxygene

Info

Publication number
EP0108141A1
EP0108141A1 EP19830902023 EP83902023A EP0108141A1 EP 0108141 A1 EP0108141 A1 EP 0108141A1 EP 19830902023 EP19830902023 EP 19830902023 EP 83902023 A EP83902023 A EP 83902023A EP 0108141 A1 EP0108141 A1 EP 0108141A1
Authority
EP
European Patent Office
Prior art keywords
analyzer
analog
digital converter
output
fuel cell
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.)
Withdrawn
Application number
EP19830902023
Other languages
German (de)
English (en)
Inventor
James A. Hoerlein
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.)
Marathon Medical Equipment Corp
Original Assignee
Marathon Medical Equipment Corp
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
Application filed by Marathon Medical Equipment Corp filed Critical Marathon Medical Equipment Corp
Publication of EP0108141A1 publication Critical patent/EP0108141A1/fr
Withdrawn legal-status Critical Current

Links

Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
    • G01N27/26—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating electrochemical variables; by using electrolysis or electrophoresis
    • G01N27/403—Cells and electrode assemblies
    • G01N27/406—Cells and probes with solid electrolytes
    • G01N27/4065—Circuit arrangements specially adapted therefor
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N33/00—Investigating or analysing materials by specific methods not covered by groups G01N1/00 - G01N31/00
    • G01N33/0004—Gaseous mixtures, e.g. polluted air
    • G01N33/0009—General constructional details of gas analysers, e.g. portable test equipment
    • G01N33/0062—General constructional details of gas analysers, e.g. portable test equipment concerning the measuring method or the display, e.g. intermittent measurement or digital display

Definitions

  • the digital oxygen analyzer of the present invention employs a fuel cell for producing a current that varies as a function of the partial pressure of oxygen in the region surrounding the fuel cell.
  • the present application is concerned with the provi ⁇ sion of a portable digital oxygen analyzer that will en ⁇ able the accurate determination of oxygen content of a gas at any time as opposed to the system of the above application Serial Number 302,602 wherein a fuel cell is employed as a sensor for an alarm device.
  • the output of a fuel cell is coupled to the signal input of an analog to digital converter, this input being modi ⁇ fied by the series or parallel interconnection of a ther- istor for temperature correction.
  • the output of the- analog to digital converter may be employed in a conven ⁇ tional manner to indicate the partial pressure of oxygen in the gas in the proximity of the fuel cell.
  • the analyzer is modified to compen ⁇ sate for ambient pressure in the vicinity of the fuel cell, since such pressure has been found to materially affect the output of the fuel cell.
  • the pressure is sensed by a pressure transducer such as a strain gauge, the voltage supply of the strain gauge being adjustable in order to enable calibration of the system.
  • the analog-to-digital converter is preferably a dividing analog to digital converter, the out- put of the pressure transducer being applied to reference terminals of the analog to digital converter so that the analyzer may be calibrated to directly display the per ⁇ centage of oxygen in the gas being tested rather than only the partial pressure of oxygen.
  • the invention thereby enables the provision of an accurate economical portable analyzer enabling the deter ⁇ mination of oxygen in a gas, such as the percentage of oxygen in atmosphere, the analyzer being readily useable without difficulty by untrained persons.
  • FIGURE 1 is a simplified block diagram of a digital oxygen analyzer in accordance with the invention
  • FIGURE 2 is a more detailed circuit diagram of the digital oxygen analyzer of FIGURE 1;
  • FIGURE 3 is a circuit diagram of a modification of the analyzer of FIGURE 2;
  • FIGURES 4 and 5 are graphs illustrating the effect of the series and parallel interconnections of a thermistor in the system of the invention;
  • FIGURES 6 and 7 are plan and side views of the fuel cell and thermistor of the analyzer of the invention.
  • FIGURE 8 is a perspective view of one embodiment of a digital oxygen analyzer in accordance with the invention. Best Mode for Carrying Out the Invention: Referring now to FIGURE 1, therein is illustrated a simplified diagram of an oxygen analyzer in accordance with the invention.
  • the analyzer includes an oxygen sen- . sor 10, which may be conventional fuel cell.
  • the oxygen' sensor 10 produces an elec ⁇ trical current proportional to the partial pressure of oxygen in the space surrounding the cell.
  • the gas diffuses through a Teflon membrane and is chemically reduced on the surface of the cathode, while a corresponding oxidition occurs at the anode of the cell.
  • the output of the cell is limited by the rate at which oxygen can diffuse across the membrane, and also by the amount of anode material available for reaction.
  • the output of the oxygen sensor 10, i.e., an electrical current proportional to the partial pressure of oxygen, is supplied to a signal conditioner 11.
  • a temperature sensor 12 for example a thermistor, is mounted in very close proximity to the fuel cell and also coupled to the signal conditioner 11 for modification of the output of the fuel cell.
  • the signal conditioner 11 is mounted in very close proximity to the fuel cell and also coupled to the signal conditioner 11 for modification of the output of the fuel cell.
  • O PI hence provides a temperature independent output dependent upon the partial pressure of oxygen surrounding the fuel cell. This output is applied as an input signal to an analog-to-digital converter 14 for producing a digital 5 signal for display on the display device 15.
  • pressure transducer 16 is provided in the proximity of the oxygen sensor, the pressure transducer providing an output that serves as a reference level for the analog-to-digital converter. If the analog-to-digital converter is inter ⁇ connected to divide the inputs applied thereto, the display
  • 15 15 may conveniently show the percentage of oxygen in the atmosphere.
  • the display may, of course, also be calibrated to show percentage of oxygen in the atmosphere even though pressure compensation is not provided, under the assumption of a determined ambient pressure.
  • a ther ⁇ mistor 20 is physically mounted on the fuel cell 10, and connected in parallel therewith. This assembly is con ⁇ nected, by way of a connector 21 to the input terminals of a type 7106A/D converter 22.
  • a calibration resister
  • 25 23 may also be connected in parallel with the input leads, this resister having a value calculated to minimize the variation of the input signal temperature in combination with the selected thermistor 20.
  • the resister 23 need not be in the proximity of the fuel cell.
  • the ambient pressure compensation system is comprised of an absolute pressure transducer 25, such as a strain gauge.
  • the output of this transducer is connected to the reference terminals of the A/D converter, whereby the output of the A/D converter is proportional to the ratio
  • the pressure transducer 26 is comprised of a strain gauge bridge, preferably a 15 PSIA absolute pressure transducer, the signal output dia- gonals of the bridge being connected to the reference voltage terminals of the A/D converter 22.
  • One of the supply terminals of the bridge is connected to the posi ⁇ tive supply and the other is connected to the output of an operational amplifier 27.
  • the operational amplifier 27 is connected as an inverting amplifier, with the in ⁇ verting input being coupled to a potentiometer 28 connected between the positive supply and the common terminal of the A/D converter.
  • the potentiometer 28 thereby enables con ⁇ trol of the operating supply connected to the strain gauge, and hence the scale factor between the signals input and reference input.
  • This scale factor is preferably set, for example, to be 100.
  • the offset of the pressure compensation may be adjusted by means of a potentiometer having its ends connected be- tween the signal outputs of the pressure transducer bridge and its arm connected to the positive supply. This may be set, for example, by adjustments of the potentiometer until a zero output is obtained from the transducer when a vacuum is applied thereto.
  • a fuel cell of the above type has a cell life dependent upon the number of hours of operation and the percent of • oxygen detected.
  • the Class C-l cell has a nominal fuel cell life of 240,000 percent hours of oxygen. This corres ⁇ ponds to one hundred days of constant exposure to 100 per- cent oxygen. In order to extend the life of the cell, it is hence desirable to expose the cell to oxygen enriched gas only when measurements are to be taken.
  • the battery 30, such as a nine volt battery, which powers the operating system of the anlyzer is connected to the circuit by way of a pushbutton switch 31, so that the analyzer is operative only when the switch is manually depressed.
  • a type 8211 low voltage detector 35 is connected to pro ⁇ vide an output to a low battery indication on the display 15.
  • the display 15 may be a seven segment display, for example, a type FED0203.
  • a simpler analyzer may be provided, as illustrated in FIGURE 3, wherein the pressure transducer is deleted, the negative reference terminal is connected to the com- mon terminal of the A/D converter, and the positive re ⁇ ference terminal is connected to a calibration potentio ⁇ meter circuit 40.
  • the signal input to the A/D pro ⁇ vides better correction for temperature changes than when the temperature dependent resister is connected in parallel with the fuel cell, as shown in the graph in FIGURE 5. It is thus preferable to interconnect the thermistor in series with the fuel cell. In the embodiment of the in ⁇ vention illustrated in FIGURES 2 and 3, however, the parallel interconnection of the thermistor has been em ⁇ ployed in view of the impracticability of achieving the required intimate contact between the fuel cell and the thermistor when the thermistor is connected in a series with the fuel cell.
  • the oxygen analyzer in accordance with the invention is readily adaptable to portable use.
  • the analyzer may be enclosed in a casing 50, for example about 2 1/2 inches wide, 1 1/2 inches deep and 4 1/2 inches high.
  • the LCD display 15 is mounted to be visible behind a cover 51 of the casing.
  • the push-button switch 31 extends through a hole in the front of the cover 51, or side of the casing 50.
  • An in- let hole 52 for air to be measured is provided in the top of the casing 50, this hole having a diameter of about 0.39 inches.
  • An exhaust hole (not shown) with a diameter of about .3 inches is provided in the rear of the casing. It will of course be apparent that other physical arrangements may be provided for the analyzer of the invention.
  • the oxygen input for the casing may be in the form of a quarter inch hose barb located on the top of the case.
  • a restrictive inlet orifice may be used to connect to pressurized gas sources, or to continuously monitor the outputs of an oxygen concentrator or like equipment.
  • a type 7126 analog-to-digital converter may be alternatively employed for a longer battery life.
  • the re- quired intimate thermal contact between the thermistor and the fuel cell was effected by employing a YSI type 44001 thermistor mounted in a 0.1 inch diameter hole drilled 0.15 inches deep in the side of the fuel cell. The thermistor was dipped in a thermal compound before. insertion into the hole, and the bare thermistor wires
  • OMPI _ were routed up the side of the fuel cell and held in place with tape. These wires were then soldered to the fuel cell contact areas, employing suitable electrical insulation.
  • the use of a series connected thermistor would have required either that the resistor be a part of the fuel cell/thermistor assembly or that three wires be connected between the fuel cell/thermistor assembly and circuit board. Either of these latter solutions would have required an insulated junction in the fuel cell assembly between the very fine thermistor wire and a comparatively coarse wire, thereby resulting in a fra ⁇ gile assembly.
  • the oxygen analyzer in accordance with the invention has been found to have an accuracy of the displayed oxy- gen concentration within •* - l percent of the reading, with the oxygen concentration displayed being within 1 percent of its final value within 60 seconds after the sensor is exposed to the gas.
  • the analyzer has an accuracy of 1 percent in the temperature range 68 to 85 F, and compen- sation for pressure variation is effective from 19.0 inches of mercury to 32.1 inches of mercury. While the invention has been described in conjunction with oxygen concentration measurement, it is understood that the in ⁇ vention can be employed to measure any constraint of a gas, with the appropriate sensor.

Landscapes

  • Chemical & Material Sciences (AREA)
  • Health & Medical Sciences (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Analytical Chemistry (AREA)
  • General Health & Medical Sciences (AREA)
  • Pathology (AREA)
  • Immunology (AREA)
  • Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Biochemistry (AREA)
  • General Physics & Mathematics (AREA)
  • Combustion & Propulsion (AREA)
  • Medicinal Chemistry (AREA)
  • Food Science & Technology (AREA)
  • Molecular Biology (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Electrochemistry (AREA)
  • Investigating Or Analyzing Materials By The Use Of Electric Means (AREA)

Abstract

Un analyseur numérique d'oxygène comprend un détecteur d'oxygène (10) relié de manière à appliquer des signaux d'entrée à un convertisseur diviseur analogique/numérique (14). Un thermistor (12) relié au circuit d'entrée de l'analyseur compense les variations thermiques ambiantes, et un transducteur de pression absolue (16) couplé aux terminaux de référence du convertisseur analogique/numérique compense les variations de pression ambiantes. Un affichage numérique (15) relié au convertisseur analogique/numérique indique le pourcentage relatif d'oxygène à proximité du détecteur d'oxygène.
EP19830902023 1982-05-07 1983-05-06 Analyseur d'oxygene Withdrawn EP0108141A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US37618982A 1982-05-07 1982-05-07
US376189 1982-05-07

Publications (1)

Publication Number Publication Date
EP0108141A1 true EP0108141A1 (fr) 1984-05-16

Family

ID=23484042

Family Applications (1)

Application Number Title Priority Date Filing Date
EP19830902023 Withdrawn EP0108141A1 (fr) 1982-05-07 1983-05-06 Analyseur d'oxygene

Country Status (2)

Country Link
EP (1) EP0108141A1 (fr)
WO (1) WO1983004101A1 (fr)

Families Citing this family (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS59170723A (ja) * 1983-03-18 1984-09-27 Hitachi Ltd 空燃比センサ
JPH063431B2 (ja) * 1984-02-08 1994-01-12 三菱電機株式会社 機関の空燃比センサ
GB8711573D0 (en) * 1987-05-15 1987-06-17 Lion Lab Ltd Measuring apparatus
GB8922126D0 (en) * 1989-10-02 1989-11-15 Normalair Garrett Ltd Oxygen monitoring method and apparatus
FR2681137B1 (fr) * 1991-09-11 1994-07-29 Superba Sa Dispositif pour mesurer et regler la concentration en air d'une enceinte.

Family Cites Families (14)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2913386A (en) * 1956-03-21 1959-11-17 Jr Leland C Clark Electrochemical device for chemical analysis
US3432418A (en) * 1965-07-19 1969-03-11 Phillips Petroleum Co Polarographic analyzer
US3518179A (en) * 1968-03-11 1970-06-30 Beckman Instruments Inc Temperature compensated electrochemical cell
US3528904A (en) * 1968-04-12 1970-09-15 Beckman Instruments Inc Range scale circuit including temperature compensation element
US3652439A (en) * 1969-02-28 1972-03-28 Niversity Of California The Appratus for measuring ph in high-pressure environments
US3685346A (en) * 1970-01-16 1972-08-22 Yellow Springs Instr Direct reading quantitative gas measuring device
US3663409A (en) * 1970-05-14 1972-05-16 Beckman Instruments Inc Pressure compensation of membranetype sensors
US3909386A (en) * 1970-11-10 1975-09-30 Energetics Science Gas detector unit
JPS5229290A (en) * 1975-08-29 1977-03-04 Meidensha Electric Mfg Co Ltd Dissolved oxygen meter
JPS5241593A (en) * 1975-09-29 1977-03-31 Yokogawa Hokushin Electric Corp Dissolved oxygen system
US4176031A (en) * 1978-03-17 1979-11-27 Fischer & Porter Co. Digital hypochlorous acid analyzer
SU767635A1 (ru) * 1978-06-20 1980-09-30 Томский Ордена Октябрьской Революции И Ордена Трудового Красного Знамени Политехнический Институт Им.С.М.Кирова Пол рограф вторых разностей
US4222006A (en) * 1978-12-18 1980-09-09 Catalyst Research Corporation Thermal composition circuit for electrochemical detectors
US4301807A (en) * 1979-12-05 1981-11-24 Novametrix Medical Systems, Inc. Apparatus and method for temperature compensated transcutaneous carbon dioxide measurement

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
See references of WO8304101A1 *

Also Published As

Publication number Publication date
WO1983004101A1 (fr) 1983-11-24

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Legal Events

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PUAI Public reference made under article 153(3) epc to a published international application that has entered the european phase

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AK Designated contracting states

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STAA Information on the status of an ep patent application or granted ep patent

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18D Application deemed to be withdrawn

Effective date: 19840712

RIN1 Information on inventor provided before grant (corrected)

Inventor name: HOERLEIN, JAMES A.