Development and Validation of an Absorption Sensor for Time-Resolved Measurements of CO and CO2

A sensor was developed for simultaneous measurements of carbon monoxide and carbon dioxide fluctuations in internal combustion engine exhaust gases. This sensor utilizes low-cost and compact LEDs that emit in the 3-5[micro]m wavelength range which are more appropriate for practical applications than the more traditionally used lasers. An affordable, fast response sensor that can measure these gases has broad application that can lead to more efficient, fuel flexible engines and regulations of harmful emissions. LEDs have a more spectrally broad and diverging emission than lasers which presented many design challenges. The optical design software ZEMAX was utilized to overcome these challenges. CO and CO[sub2] LED measurements are conducted in their fundamental bands centered at 4.7[micro]m and 4.3[micro]m, respectively, while a reference LED at 3.6[micro]m is used as a reference for H2O. Tests were carried out using a simple flow cell for validation and calibration of the instrument. The sensor was able to see 0.1% changes in CO2 and about 0.3% changes CO. No interference between CO and CO2 was observed