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
  • G01N27/72—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating magnetic variables
  • G01N27/74—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating magnetic variables of fluids

Definitions

• This invention relates to sensors and systems for measuring the concentration of oxygen present in a mixture of gases, wherein the sensor relies upon detection of thermal effects due to a wind formed in a magnetic field within the measuring device as a result of the paramagnetism of oxygen present in the mixture.
• a variety of such devices have been described for measuring oxygen concentration, and these magnetic wind oxygen sensing systems rely on the fact that when placed in a magnetic field, the paramagnetic oxygen will exert a pressure in a certain direction, while the remaining components of the mixture, which is substantially formed of diamagnetic gases, are unaffected by the local field.
• a mixture of oxygen with diamagnetic gases behaves, from the magnetic point of view, as a single component with a magnetic property (magnetic susceptibility) equal to the weighted average of the susceptibilities of each of the components.
• a magnetic wind oxygen sensing device that provides a local magnetic field defined, for example, by magnetic pole pieces, and has a plurality of thermal elements arranged in a bridge at the local magnetic field to measure oxygen concentration present in a surrounding gas mixture.
• the device creates a magnetic wind and detects thermal effects induced in the elements as a result of the wind.
• the wind is generated by heating elements positioned at a region of high field intensity. The heat locally reduces paramagnetism of oxygen present in the gas, causing a pressure drop compared to unheated gas of identical composition, so that cooler gas in the magnetic field displaces the warmed gas and flows over the heater elements.
• Each wind generator is located between two sensing elements, and these are positioned so that, while both receive heat from the wind generator, one sensor is somewhat cooled (by flowing gas from the lower temperature region of the measuring cell as a whole, sometimes simply referred to as "ambient” herein) and the other is somewhat heated, respectively, by the wind thereby generated.
• the two sensing elements are at the same temperature (which is also the temperature of the gas immediately surrounding them), due to the heat received from the wind generator located centrally between them.
• the zero point remains fixed, even when conductive properties of the surrounding (but stationary) gas change.
• Figure 3 A illustrates one suitable sensing circuit for the practice of the invention
• Figure 3B illustrates another suitable sensing circuit for the practice of the invention
• pairs sensing elements are arranged to be passively heated or cooled, while always residing near the surrounding temperature of a local measurement region, which may, for example, be maintained at a temperature only slightly above ambient.
• the invention positions sensing elements upstream and downstream, respectively, of each of a pair of heater elements in a magnetic wind, and forms a sensing bridge of the sensing elements.

Landscapes

• Chemical & Material Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Electrochemistry (AREA)
• Physics & Mathematics (AREA)
• Health & Medical Sciences (AREA)
• Life Sciences & Earth Sciences (AREA)
• Analytical Chemistry (AREA)
• Biochemistry (AREA)
• General Health & Medical Sciences (AREA)
• General Physics & Mathematics (AREA)
• Immunology (AREA)
• Pathology (AREA)
• Investigating Or Analyzing Materials By The Use Of Magnetic Means (AREA)
• Investigating Or Analyzing Materials Using Thermal Means (AREA)

Priority Applications (2)

Applications Claiming Priority (2)

Publications (1)

Family

ID=25191197

Family Applications (1)

Country Status (4)

Cited By (1)

Families Citing this family (3)

Citations (3)

Family Cites Families (4)

• 2001
  • 2001-03-13 US US09/805,302 patent/US6389880B1/en not_active Expired - Fee Related
• 2002
  • 2002-02-25 WO PCT/US2002/005700 patent/WO2002073175A1/en not_active Ceased
  • 2002-02-25 JP JP2002572389A patent/JP2004529332A/ja not_active Withdrawn
  • 2002-02-25 EP EP02707885A patent/EP1370852A1/en not_active Withdrawn

Patent Citations (3)

Also Published As

Similar Documents

Legal Events