Modified noble metal catalyst based calorimetric sensor and method

A modified noble metal catalyst based calorimetric sensor for sensing non-methane hydrocarbons in an automotive exhaust gas stream comprising:

• a first sensing element having an output for providing a signal indicative of a concentration of indicative of non-methane hydrocarbons, hydrogen (H.sub.2), and carbon monoxide (CO), wherein first sensing element is constructed with a heavily poisoned noble metal catalytic material dispersed through a body portion of the first sensing element, and a first temperature measurement device for providing a signal having a magnitude indicative of a first temperature proximate the heavily poisoned noble metal catalytic material;
• a compensating sensing element having an output for providing a compensating signal indicative of a concentration of hydrogen (H.sub.2) and carbon monoxide (CO), wherein the compensating sensing element is constructed with a lightly poisoned noble metal catalytic material dispersed through a body portion of the compensating sensing element, and a compensating temperature measurement device for providing a compensating signal having a magnitude indicative of a compensating temperature proximate the lightly poisoned noble metal catalytic material, wherein a poisoning concentration of the heavily poisoned noble metal catalytic material is greater than a poisoning concentration of the lightly poisoned noble metal catalytic material;
• and
• a circuit for combining the signal and the compensating signal, and for providing a combined signal indicative of a measure of non-methane hydrocarbons in the automotive exhaust gas stream.

A method for detecting non-methane hydrocarbons in an automotive exhaust gas stream comprising the steps of:

• exposing a heavily poisoned noble metal catalyst to the automotive exhaust gas stream and deriving a signal indicative of a temperature proximate the heavily poisoned noble metal catalyst;
• exposing a lightly poisoned noble metal catalyst to the automotive exhaust gas stream and deriving a compensating signal indicative of a temperature proximate the lightly poisoned noble metal catalyst;
• and
• combining the signal and the compensating signal and providing a signal indicative of a concentration of non-methane hydrocarbons in the automotive exhaust gas stream dependent thereon.