EGR distribution and fluctuation probe based on CO2 measurements

A diagnostic system for determining CO2 concentration comprising:

• a swept-λ laser having a sweep range including a CO2 absorption feature and at least one substantially zero absorption region;
• a beam splitter disposed adjacent to said laser to split an output light beam of said laser into a plurality of light beams;
• a plurality of probes coupled to said beam splitter, each of said probes being uniquely associated with a corresponding one of said plurality of light beams, each probe including:
• a single port housing;
• a sampling chamber defined within said housing;
• a pitch optical cable disposed within said housing, said pitch optical cable conveying said light beam to said sampling chamber;
• a catch optical cable disposed within said housing, said catch optical cable conveying said light beam from said sampling chamber;
• a mirror disposed adjacent said sampling chamber for reflecting said light beam to said catch optical cable;
• and
• a processor for determining CO2 concentration as a function of at least one light beam conveyed from said sampling chamber of at least one of said plurality of probes.

A method for determining concentration of a substance in a fluid stream, comprising the steps of:

• providing a probe with a sampling chamber;
• providing a swept-λ laser having a sweep range including a significant absorption feature of the substance and at least one substantially zero absorption region;
• producing a light beam with the laser;
• directing the light beam into said probe and through said sampling chamber, the sampling chamber containing the fluid stream to be measured;
• receiving the light beam at a detector, the detector producing an output signal representative of light intensity in the light beam;
• normalizing the output signal with a processor as a function of light intensity in the zero absorption region;
• and
• determining the concentration of the substance with a processor as function of the output signal of the detector, said normalizing step occurring prior said determining step.