Oxygen measuring apparatus and method with automatic temperature compensation

An apparatus for measuring the oxygen content of a gas comprising;

• a tube of solid electrolyte material capable of oxygen ion conductivity, said tube having a closed end in communication with said gas and an open end in communication with atmospheric air, a first electrode disposed on the inside surface of said tube, a second electrode disposed on the outside surface of said tube;
• a heater in close proximity to said tube for heating said tube;
• indicating means for indicating the oxygen content of said gas;
• first and second electrical wire means in series extending between said first electrode and said indicating means;
• said first and second wire means comprising dissimilar metals, respectively, and joined to each other at a position removed from said first electrode to form a first thermocouple junction;
• said first wire means comprising the same metal as said first electrode and connected to said first electrode;
• said second wire means connected to said indicating means;
• third wire means extending between said second electrode and said indicating means;
• said third wire means and said second electrode comprising dissimilar metals, respectively, and joined to each other to form a second thermocouple junction;
• said third wire means comprising the same metal as said second wire means;
• said first and said second thermocouple junctions generating first and second emf's respectively;
• and
• said first and second emf's opposing each other.

An apparatus for measuring the oxygen content of a gas comprising;

• a tube of solid electrolyte material capable of oxygen ion conductivity, said tube having a closed end in communication with said gas and an open end in communication with atmospheric air, a first platinum electrode disposed on the inside surface of said tube, a second platinum electrode disposed on the outside surface of said tube;
• a heater disposed within said tube for heating said tube;
• indicating means for indicating the oxygen content of said gas;
• first and second electrical wire means in series extending between said first electrode and said measuring means;
• said first and second wire means comprising dissimilar metals, respectively, and joined to each other at a position removed from said first electrode to form a first thermocouple junction;
• said first wire means comprising platinum and connected to said first electrode;
• said second wire means comprising nickel and connected to said indicating means;
• third wire means extending between said second electrode and said indicating means;
• and
• said third wire means comprising nickel and joined to said second electrode to form a second thermocouple junction.

A method for measuring the oxygen content of a gas comprising;

• passing said gas to the outside of a tube of solid electrolyte material capable of oxygen ion conductivity, said tube having a closed end in communication with said gas and an open end in communication with atmospheric air, said tube having an outside electrode and an inside electrode;
• heating said tube to maintain a control temperature at said tube;
• the oxygen in said gas generating an electrical signal at said tube and passing said signal through said electrodes to an oxygen indicating means for indicating the oxygen content of said gas;
• measuring the ambient temperature in the vicinity of said tube;
• and
• automatically compensating for any offset in indication of oxygen content due to a difference between said ambient temperature and said control temperature.

The method for measuring the oxygen content of a gas comprising;

• passing said gas to the outside of a tube of solid electrolyte material capable of oxygen ion conductivity, said tube having a closed end in communication with said gas and an open end in communication with atmospheric air;
• said tube having an outside electrode and an inside electrode;
• heating said tube to maintain a control temperature at said tube;
• the oxygen in said gas generating a first electrical signal at said tube and passing said first electrical signal through said electrodes to an oxygen indicating means for indicating the oxygen content of said gas;
• measuring by thermocouple the ambient temperature in the vicinity of said tube to produce a second electrical signal based on the difference between said control temperature and said ambient temperature;
• passing said second electrical signal through said electrodes to said oxygen indicating means;
• and
• said first electrical signal and said second electrical signal opposing each other thereby automatically compensating for any offset in the indication of oxygen content due to a difference between said control temperature and said ambient temperature.