Exhaust opacity measuring device

A remote sensing system for remotely determining the opacity of a vehicle exhaust plume for a diesel powered vehicle comprising:

• a radiation source arranged to pass radiation through an exhaust plume of a motor vehicle;
• one or more detectors arranged to receive the radiation after it passes through the exhaust plume of the motor vehicle and generate at least one signal indicative of the intensity of radiation in at least two different detection bands received at the one or more detectors;
• a first of said detection bands being selected to include a wavelength of radiation at which there is substantial absorption of radiation by carbon monoxide, and a second of said detection bands being selected to include a wavelength of radiation at which there is substantially no absorption of radiation by a gaseous component of a vehicle exhaust plume;
• and
• a processor programmed to determine the difference between the intensity of the radiation provided by the radiation source in the at least two different detection bands and the intensity of the radiation received by the one or more detectors in the at least two detection bands, based on the at least one signal generated by the one or more detectors, and to disregard the radiation intensity measurement in the second of said detection bands for exhaust opacity based at least in part on the determined intensity difference in the first detection band.

A method for remotely sensing exhaust emissions to determine the opacity of an exhaust plume from a motor vehicle comprising the steps of:

• a) passing radiation from a radiation source through an exhaust plume of a motor vehicle;
• b) receiving the radiation at one or more detectors after it passes through the exhaust plume of the motor vehicle;
• c) generating at least a first signal indicative of the intensity of the radiation received at the one or more detectors in a first detection band which includes a wavelength at which there is substantial absorption of radiation by a gaseous component of the exhaust plume, and a second signal indicative of the intensity of the radiation received at the one or more detectors in a second detection band which includes a wavelength at which there is substantially no radiation absorbed by a gaseous component of the exhaust plume;
• d) determining from the first and second generated signals the difference between the intensity of the source radiation and the intensity of the radiation received at the one or more detectors in the first and second detection bands;
• e) comparing the determined differences in said first and second detection bands to obtain a measurement of the exhaust opacity;
• and
• f) discarding the radiation intensity measurements in said first detection band if the exhaust opacity exceeds a predetermined threshold level.

A method for remotely sensing exhaust emissions to determine the opacity of an exhaust plume from a diesel powered vehicle comprising the steps of:

• a) passing radiation from a radiation source through an exhaust plume of a motor vehicle;
• b) receiving the radiation at one or more detectors after it passes through the exhaust plume of the motor vehicle;
• c) generating at least a first signal indicative of the intensity of the radiation received at the one or more detectors in a first detection band which includes a wavelength at which there is substantial absorption of radiation by carbon monoxide, a second signal indicative of the intensity of-the radiation received at the one or more detectors in a second detection band which includes a wavelength at which there is substantially no radiation absorbed by a gaseous component of the exhaust plume;
• and
• d) determining from the first and second generated signals the difference between the intensity of the source radiation and the intensity of the radiation received at the one or more detectors in the first and second detection bands;
• e) determining exhaust opacity from said intensity difference in said second detection band;
• f) discarding the determined exhaust opacity if the intensity difference in the first detection band does not fall within a predetermined correlation with the exhaust opacity.