Description

Vehicle exhaust emissions have historically been a major contributor to the world's air pollution problems. The direct relationship between reduced vehicle emissions and cleaner, healthier air is very well understood. AIM's automotive emissions measurement analyzers are being used worldwide to help identify and repair "dirty" vehicles.

The AIM IR and UV DOAS system collects direct real-time data [less than 10 msec for the UV and less than 80 msec for the IR] on a set of 25 or more analytes (such as NO, NO2, NH3, BTX, SO2, CO, CO2, HCs, etc ) emitted from vehicle exhausts as the vehicles intercept the light beam projected across the driving lane. Both IR and UV beams, containing all wavelengths from 180 nm in the UV to 5.5 microns in the IR, are projected through the measurement path. An AIM proprietary open-path projection system optimizes instrument sensitivity, and capture of the exhaust plume. The analyzers continuously reads, stores, and overwrites the background spectra. When a vehicle intercepts the beam, the most recent spectra set is saved and logged to the hard disk drive.

Fast signal collection (on the order of 10's of msec) and high speed A/D conversion followed by state-of-the-art data processing, including an AIM developed partial least squares singular value decomposition algorithm, yields the concentration of the measured analytes. The estimated total system response time to measure all 25 measurements is 0.08 second. Multiple readings are made and averaged. The data is then stored for subsequent post processing to analyze for unknowns, if desired. The systems are calibrated by passing cylinder gas through internal inline cal cells; but experience has shown no detectable drift over a 4 to 6 month operating period.

Data has been collected on-road vehicles, plus many parking lot tests, included diesel, gasoline, natural gas and methanol fueled automobiles and trucks. It has been shown that the data can be applied for "clean-screening", the detection of high emitters, as well as for investigating the chemical composition of the plume and probing fast reactions occurring in the plume. Results have been presented in ES&T, as well as at both the CRC and ACS Annual Conferences.

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Technical Articles Available on Vehicle Analyzers

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