Spectroscopic remote sensing exhaust emission monitoring system

Abstract

A spectroscopic IR and UV-vis absorption remote exhaust emission monitoring system and sensing instrument for non-invasive, multicomponent analysis of the exhaust plume emitted by in-use vehicles. The concentration of CO, CO HC, NO, N O, C H , NH , SO , Aromatic hydrocarbons, aldehydes, HONO, NO , and dust, among others and in any combination there-of, in such a mixture can be determined in real-time, or via post-processing of stored spectral data. The sensor employs an IR and a UV-vis sources, and the physically offset, collimated beams traverse the probed air column, typically a roadway, a plurality of times, before returning to the instrument. Although the IR and UV-vis beams converge at the optics opposite the instrument, they are not coaxial and, thus, do not require an optical device (i.e., dichroic beam splitter) to separate them. The separate IR and UV-vis beams are focused on the slits of rapid spectrometers, where they are analyzed to yield wavelength-resolved spectra (i.e., graphs of digital signal intensity versus radiation wavelength). These spectrometers can either be rapid scanning dispersive devices, dispersive devices employing linear or two-dimensional detector arrays, or Fourier transform spectrometers. The graphs are converted into absorbance spectra and are subsequently processed with pattern recognition algorithms and a spectral reference database to afford analyte concentration.