Method and apparatus for measuring the O.sub.2 content of a gas

A method for obtaining an electrical signal which is a function of the O.sub.2 content of a gas, the method comprising:

• connecting a first resistor made of titania in series with a second resistor having a predetermined resistance, the resistance of the titania resistor varying as a function of both the temperature and the oxygen content of the gas to which it is exposed;
• connecting a third resistor, the resistance of which varies as a function of the temperature of the gas to which it is exposed, to a fourth resistor having a predetermined resistance, said third resistor having about the same resistance-temperature characteristics as said titania resistor over a predetermined temperature range of said gas;
• connecting said first and second resistor in parallel relationship with said third and fourth resistors;
• applying a voltage across said resistors;
• exposing said resistors to a gas;
• obtaining a first electrical signal which is a function of the voltage across one of said first and second resistors;
• obtaining a second electrical signal which is a function of the voltage across one of said third and fourth resistors;
• and
• generating an output signal from said first and second electrical signals which is a function of said first and second electrical signals.

An electrochemical oxygen sensing apparatus for obtaining an electrical signal which is a function of the oxygen content in a gas, said sensing apparatus comprising:

• a first resistor having a resistance which varies as a function of the temperature and oxygen content of the gas to which it is exposed;
• a second resistor having a resistance r1;
• a third resistor having a resistance which varies as a function of the temperature of the gas to which it is exposed;
• a fourth resistor having a resistance r2;
• means for electrically connecting said first resistor in series with said second resistor;
• means for electrically connecting said third resistor in series with said fourth resistor;
• means for electrically connecting said first and second resistor in parallel relationship with said third and fourth resistor;
• and
• means for applying voltage across said first and second resistor and said third and fourth resistor;
• and
• means for generating an output signal which is a function of the voltage across the first resistor and the voltage across said third resistor, whereby when a voltage is applied to said resistors and said first and third resistors are exposed to a gas, said output signal is related to the oxygen content of the gas.

An electrochemical oxygen sensing apparatus for obtaining an electrical signal which is a function of the oxygen content in a gas, said sensing apparatus comprising:

• a first resistor comprised of a titania material;
• a second resistor having a resistance r1;
• a third resistor comprised of a material, the resistance of which varies as a function of the temperature of the gas to which it is exposed, said third resistor having about the same resistance-temperature characteristics as said first resistor over a predetermined temperature range of said gas;
• a fourth resistor having a resistance r2;
• means for electrically connecting said first resistor in series with said second resistor;
• means for electrically connecting said third resistor in series with said fourth resistor;
• means for electrically connecting said first and second resistor network in parallel with said third and fourth resistor network;
• means for applying a voltage across said first and second resistor and said third and fourth resistor;
• means for obtaining a first electrical signal which is a function of the voltage across said first resistor;
• means for obtaining a second electrical signal which is a function of the voltage across said third resistor;
• and
• means for comparing said first electrical signal to said second electrical signal and providing an output signal.