Ratiometric device

An article of manufacture comprises at least one non-transitory, tangible machine readable storage medium containing executable machine instructions for ratiometric measurement which comprise:

• generating a first current and a second current different from the first current;
• switching between the first and second currents at a current-select program;
• measuring, from a sensor device responsive to a gas, a sensor-cold temperature T(cold,sens) in response to the first current and a sensor-hot temperature T(hot,sens) in response to the second current;
• measuring, from a reference device a reference-cold temperature T(cold,ref) in response to the first current and a reference-hot temperature T(hot,ref) in response to the second current;
• wherein the reference device is either less responsive or more responsive to the gas than the sensor device;
• calculating a temperature difference ratio based on this equation:
• Δ
• 
• 
• T
• sens
• Δ
• 
• 
• T
• ref
• 
• =
• T
• hot
• ,
• sens
• -
• T
• cold
• ,
• sens
• T
• hot
• ,
• ref
• -
• T
• cold
• ,
• ref
• generating a thermal conductivity device output signal based on the temperature difference ratio.