CN1338044A

CN1338044A - Exhaust opacity measuring device

Info

Publication number: CN1338044A
Application number: CN 99816128
Authority: CN
Inventors: 约翰·D·迪多梅尼科; 克雷格·S·伦德尔; 詹姆斯·A·约翰逊; 唐纳德·H·斯特德曼; 加里·A·毕晓普
Original assignee: ENVIROTEST SYSTEM CORP
Current assignee: ENVIROTEST SYSTEM CORP
Priority date: 1998-12-11
Filing date: 1999-12-10
Publication date: 2002-02-27

Abstract

A remote emissions sensing system and method for sensing exhaust emissions from motor vehicles is provided where the system determines the opacity of an exhaust plume. The system comprises a radiation source that emits radiation which is passed through the exhaust plume of a motor vehicle to one or more detectors arranged to receive the radiation. A processor calculates the difference between the intensity of source radiation and the intensity of the radiation received by the detectors in first and second detection bands. The intensity difference in the second detection band measures exhaust opacity. If the exhaust opacity exceeds a predetermined level, the emissions data from other detection bands may be flagged as suspect or discarded. Alternatively, for a diesel powered vehicle, the exhaust opacity determination can be validated by a measurement of carbon monoxide in the exhaust plume.

Description

Exhaust opacity measuring device

Technical field

The present invention relates to a kind of long-range emission sensing system and method that is used for sensing automobile exhausting emission, wherein this system determines the turbidity of an exhaust plume (plume).

Technical background

Long-range emission sensing (RES) system is the system that people are familiar with.The patent No. is to have disclosed such system in 5,210,702 the United States Patent (USP), and it comprises an electromagnetism (EM) radiation source, and this radiation source is configured at motor road and during through this system, makes a branch of EM radiation pass the exhaust plume of motor vehicle.This system also comprises one or more detector, and detector is configured to after the exhaust plume of vehicle is passed in radiation, received radiation.Detector can be associated one or more wave filter with one or more detector, so that can determine to have the intensity of the EM radiation of specific wavelength or wavelength coverage.Can be selected wavelength easily, with corresponding to (for example hydrocarbon (HC), carbon monoxide (CO), carbon dioxide (CO in the exhaust plume ₂), nitrogen oxide (NO _X) molecular substance (spicies) (for example NO and the NO that are paid close attention to ₂) wavelength that absorbed.One or more detector output voltage representative is by the intensity of the measured EM radiation of this detector.

Then, these voltages are input to a processor.This processor calculate the known strength of light source and the intensity surveyed by detector between intensity difference, with the amount of determining to be absorbed (based on the predetermined wavelength that is associated with those materials) by the specific molecular material.According to measured uptake, can the concentration of one or more molecular substance in the emission be determined by a kind of known mode.

Chen, people such as G. have disclosed a system that is used for the remote sense exhaust turbidity in " feasibility of remote sense heavy vehicle particulate emissions thing (Feasibility of RemoteSensing of Particulate Emissions From Heavy-Duty Vehicles) " literary composition that AIAE American institute of automobile engineers (1996) is delivered.In this system, with the wavelength measurement turbidity of 710nm, and and CO ₂Measurement result is associated.

Existing RES system exists many defectives, and has been subjected to many-sided restriction.The incidence of the reading that these factors may lead to errors, the high relatively incidence that abandons data or high relatively " (flagged) of mark " test result.These and other problem all may influence the work of RES system.

At least work is carried out in the absorption (or transmittance) of the light of some RES components of system as directed ground by determining to pass the exhaust plume.By determining absorption/transmittance, can determine the concentration of those molecular substances in the emission specific wavelength (absorbing the wavelength at EM radiation place corresponding to each molecular substance in the exhaust plume).A problem is that various extraneous factors may influence measured intensity, and cause error.For example, if measured intensity because of the light scattering of particle in the exhaust plume, rather than by the molecular substance of being paid close attention to the absorption of radiation and weaken, this may cause error so.These and other shortcoming is determined to exist.

Summary of the invention

An object of the present invention is to overcome in the existing equipment shortcoming of these and other.

Another object of the present invention provides a kind of long-range emission sensing system and method that can telemonitoring vehicle exhaust turbidity.

Another purpose of the present invention is by measuring exhaust turbidity and utilizing measured exhaust turbidity to guarantee the precision of other measurement result, to improve the degree of accuracy of long-range emission sensing system and method.

A further object of the present invention is to provide the exhaust turbidity surveillance coverage to existing emission surveillance equipment.

These and other purpose of the present invention can be achieved by different embodiment according to the present invention.According to an embodiment, a kind of RES system and method comprises a radiation source, and this radiation source is configured so that the exhaust plume of passing motor vehicle through a branch of radiation in season of this system at motor road.One or more detector is configured to and receives this radiation after the exhaust plume of vehicle is passed in radiation.

One or more detector is exported a voltage, and this voltage is corresponding to the intensity of the radiation that this detector received.Then, these voltages are input to a processor, intensity difference between the known strength of this processor calculating light source and the intensity that detector is detected is with the amount (based on the presetted wavelength that is associated with this molecular substance) of determining that the specific molecular material is absorbed.According to measured uptake, can determine the concentration of one or more molecular substance in the emission.

According to an aspect of the present invention, the output of a reference detector is provided for a processor, and is monitored by this processor, to determine the turbidity of each exhaust plume.According to measured turbidity, can take a predetermined actions.For example,, can analyze the emission data so if exhaust turbidity surpasses a predetermined level, producing test result (by a kind of known mode), but also can become to suspect test result " mark " or abandon.

For those skilled in the art, by above general introduction and the following detailed description, other purpose of the present invention and advantage will be conspicuous.

Brief description of the drawings

Fig. 1 has described the long-range emission sensor device (RES) according to one embodiment of the invention.

Fig. 2 has described a data analysing method according to one embodiment of the invention.

Fig. 3 has described a disposal system according to one embodiment of the invention.

Fig. 4 has described the process flow diagram according to a method of one embodiment of the invention.

Detailed description of preferred embodiment

Fig. 1 has described a RES according to one embodiment of the invention.This RES measures the emission from a vehicle 10.This RES comprises a source 12, is used to generate radiation 20.When vehicle 10 tunnel during through RES, radiation 20 is guided through the exhaust plume 16 of vehicle 10.Shift eyeglass 18 received radiations 20, and give one or more detector 14 radiation 20 by plume 16 as returning radiative transfer.Detector 14 is configured to described returning and after the exhaust plume 16 of vehicle 10 is passed in radiation 22 it is measured.Detector 14 can be associated a wave filter (not shown in the drawings) with one or more detector 14, so that can determine to have the intensity of the radiation of specific wavelength or particular range of wavelengths by leach all wavelengths except that specific wavelength or particular range of wavelengths from return radiation 22.In addition, also can be used as source 12 to tuning laser,, in this case, will not need wave filter to generate the radiation 20 of a specific wavelength or particular range of wavelengths.

Can select wavelength easily, with corresponding to by the molecular substance of being paid close attention in the exhaust plume (for example HC, CO, CO ₂, NO, NO ₂(to call NO in the following text _X) or other molecular substance) wavelength that absorbed.Obtain representative one or more detector output voltage by the intensity of the measured radiation 22 of this detector 14.These detector output voltages are input to a processor 100.Detector 14 can be any suitable detector, for example spectrometer, indium antimonide or other known photodetector.

Preferable way is, source 12 is maintained on the stable substantially temperature, for example can adopt such method: source 12 is enclosed in the housing, with isolated itself and atmospheric conditions (for example sun, wind and rain).The temperature variation at 12 places may cause the additional error in the measurement result in the source.

Processor 100 can calculate the initial strength of radiation 20 and the intensity of the radiation 22 that detected by detector 14 between intensity difference, with determine by specific molecular substance with presetted wavelength that this molecular substance is associated on to the uptake of radiation.According to measured uptake, can be determined the concentration of one or more molecular substance in the emission by a kind of known mode.Usually a plurality of (for example, 50) measurement result is got by these systems on a preset time cycle (for example, 0.5 second), then these data points is associated, and they are analyzed, to determine the concentration of target discharge thing material.

According to one embodiment of the invention, disposal system 100 can be carried out various function, comprises the concentration of determining each emission composition.As discussed above, a plurality of passages of the equipment monitor among Fig. 1, each passage are used for a kind of independently emission composition.

According to one embodiment of the invention, RES can be used for diesel vehicle, particularly heavy-duty diesel vehicle, for example truck and motorbus.The present invention also can be used for measuring the concentration of the various emission compositions in the diesel engine truck exhaust and the amount of specific emission.Gas and particulate emissions thing have caused significant pollution to environment jointly.Particularly, heavy-duty diesel vehicle has produced a large amount of NO _XAnd particulate emissions thing.Because the possible carcinogenicity of diesel particulate emission is controlled this emission strictness usually.

Exhaust turbidity is a measured value to vehicle particulate emissions thing.

In the process of measuring vehicle emission turbidity, can carry out turbidity measurement, CO measurement and CO ₂Measure, to obtain a reliable and accurate measured value turbidity.Any measurement to turbidity comprises a certain error factor inherently, and reason is that surrounding air waters down the exhaust plume.When measuring turbidity to CO ₂The corresponding measurement that concentration is carried out is with same water down of reflection surrounding air to the exhaust plume.According to the CO in the predetermined exhaust plume ₂Aspiration level, get turbidity measured value and a CO ₂A ratio of measured value has reduced to water down the factor, thereby causes an accurately measurement to turbidity.

For being vehicle powered with diesel oil, by the turbidity measurement result is compared with a measurement result of taking from the CO in the same exhaust plume in the identical substantially time, the turbidity measurement result can further be verified.The CO amount in the plume and the value of the turbidity in the plume are proportional.Therefore, if the value height of turbidity, the CO amount also should be high so.If CO amount is low, and the value of the turbidity of being surveyed is high, so this can be used as turbidity measure in possible error indication or because of the indication of other factors to the possible interference of measuring.

In a better embodiment, used the independently turbidity passage of a definite turbidity.Preferable way be make this independently passage use the radiation of about 0.30～1.50 micron wave length.This wavelength coverage is expected to provide more accurate turbidity to measure.A system so also can comprise a CO at least ₂, CO and reference channel.In this case, noise around reference channel is used for monitoring and correction appear at the low-level particulate material of exhaust plume.

According to one embodiment of the invention, can be described with reference to the method that 2 couples one in figure is used to analyze emission.In step 300, provide some standard.These standards that are used for the analysis to measure result may be not quite similar, and depend on related specific emission.In step 302, if these standards are satisfied, in step 310, this process turns back to step 300 so, to determine whether also having more standard to be analyzed.This process continues, until there not being more standard to be analyzed in step 310.

In step 302, if these standards are satisfied, whether so in step 304, this process determines whether these standards are not satisfied a kind of like this degree: prepare in step 306 they to be abandoned, perhaps prepare in step 308 simply they marks in addition.

After these standards have been satisfied, in step 320, can compensate the result at environmental conditions.In step 322, system compensates at system condition and in step 324, can further be analyzed data.With reference to next embodiment of the present invention, can be understood better whole this method.

According to one embodiment of the invention, standard can comprise the checking to turbidity.According to this embodiment, the output of one or more detector of RES system is input to processor 100, as described at Fig. 3.Processor 100 can comprise an exhaust turbidity determining unit 102.Processor 100 can be carried out various known functions, comprises the concentration of determining all gases emission.In addition, processor 100 also can be determined exhaust turbidity by exhaust turbidity determining unit 102 according to the measurement of being carried out.

According to one embodiment of the invention, by wavelength turbidity to be measured with about 3.9um, exhaust turbidity determining unit 102 can use the reference channel of RES system to determine exhaust turbidity.Exhaust turbidity determining unit 102 from reference channel and at least the passage paid close attention to of another one receive measurement result.According to an embodiment, the passage of being paid close attention to can be CO ₂Passage.

For each measured particular time interval, if the intensity of reference channel is less than the input intensity by 12 normal radiation 20 that generate of radiation source, processor 100 weakening and CO reference channel intensity so ₂Weakening of intensity on the passage compares, if the strength degradation of the reference channel of being surveyed can be concluded so: the particle in the exhaust plume is just stopping up or the part of deflection radiation 20, so this part does not turn back to detector 14 as returning radiation 22.Turbidity results from by appearing at particulate material in the exhaust plume to the scattering and the absorption of radiation.

According to one embodiment of the invention, can be used for definite turbidity to the output of one or more detector from the exhaust plume that is detected vehicle.The output of detector (voltage level) can be monitored by processor 100.Can be used to the voltage drop in the reference channel to indicate and the turbidity of definite exhaust.Therefore, can be selected specially wavelength or wave band that reference channel is surveyed, so that the composition of emission (comprises CO ₂, CO, HC and NO _X) do not disturb the turbidity reading.

For determining of the turbidity in the exhaust plume, can comprise determining that from the turbidity in the exhaust plume of heavy-duty diesel vehicle the exhaust of this vehicle may comprise particulates such as dried carbon black.Generally, the big I of most diesel oil particle is between 0.02～0.5 micron scope.According to the present invention, can be used to the output of one or more detector to calculate the turbidity of the exhaust plume of a heavy-duty diesel vehicle that is detected.The output of detector can be monitored by processor 100, promptly monitors the variation of the radiation intensity that the particle (for example carbon black) because of the diesel exhaust gas plume causes.Then, the intensity of variation of the radiation intensity that is detected is used to measure the turbidity of diesel exhaust gas emission.

Can be used for proofreading and correct the gasmetry wavelength that is used for ambient noise, turbidity and other factors to the minimizing of measured reference channel intensity, because contaminant gases does not absorb on reference wavelength.Then, can convert the wavelength absorption of measured pollutant to visible concentration value.If one of these visible concentration values surpass a predetermined minimum value at least, then can be the concentration of pollutant and measured CO ₂Associate.Slope is measured pollutant and measured CO ₂Ratio.These slopes can be used for carrying out other calculating, and are described as other place of this paper.

In a preferred embodiment, the turbidity measurement is used for verifying the measurement result of other composition of exhaust plume.Have a large amount of particulate materials in the high turbidity value representation exhaust plume, exist a large amount of particulate materials may cause the scattering or the absorption of radiation on one or more characteristic wavelength of the various compositions that are used for the exhaust plume.

In such a case, when high turbidity occurred, RES can be marked as the reading of being got suspection or invalid.Better way is that delay a period of time reads these more afterwards and is marked as invalid reading and additional reading, is precipitated out from exhaust cigarette center pillar to allow sizable a part of particulate material.In order to realize this point, RES can monitor turbidity and CO reading, until for getting various exhaust gas compositions (for example CO, CO ₂, HC, NO and NO ₂) reading, turbidity and CO concentration have dropped to one and have thought under the acceptable predetermined level.After this time delay, can use CO ₂Reading verified the existence of the plume that is enough to be used in measuring, because can be according to such as factors such as type of vehicle, fuel type and environmental conditionss, to the desired CO of a concrete vehicle exhaust row plume ₂Concentration is estimated.In this mode, RES can provide the accurate measurement result of exhaust gas composition, even has one will introduce the high turbidity of such measurement result to a sizable error usually the time when initial exhaust plume.

Be subjected to the influence of various factors, for example be subjected to the influence of air, wind and vehicle rear turbulent flow, the number percent turbidity is easy to rapid dilution.Because can be CO ₂Reading is used as a tracking symbol (tracer) in the descried place of exhaust plume, so and if CO ₂Related out of true (promptly aspect slope, having big error), can think since then that so the turbidity measurement result for example, from the dust of tire, and is abandoned this reading from another source.If association is accurate (promptly having little error aspect slope), so measured slope be multiply by an association factor, for example multiply by 1000, depend on the scale and the unit of employed measurement, it has caused a standardized turbidity.

Fig. 4 has described the process flow diagram of a method that is used to survey exhaust turbidity according to an embodiment of the invention.In step 200, a reference channel and one or more emission passage (CO for example ₂Passage) output can be received by processor 100.Can carry out various checkings to data, error prevents or the signal Processing routine, to guarantee that plume enough is used to carry out turbidity and determines.In step 202, if these checking routines determine that plume is insufficient, so plume may be marked as suspection or abandon, measure to prevent wrong turbidity.

Yet, if measurement result is verified that in step 204, processor 100 can be determined the number percent turbidity according to all the other measurement results so.Particularly, by calculating the slope and the CO of reference channel output ₂The ratio of the slope of passage output can be determined the number percent turbidity, can be changed these results, so that a woods lattice Germania scale equivalent result to be provided.In brief, a woods lattice Germania scale equivalent result is determined by making the number percent turbidity equal the number between 0～5.Woods lattice Germania scale and turbidity contrast are as follows:

Turbidity	Woods lattice Germania equivalence
Turbidity	Woods lattice Germania equivalence	0％	0
15％	1	0％	0
15％	1	30％	2
50％	3	30％	2
50％	3	70％	4
100％	5	70％	4

After the number percent turbidity was determined, people may wish by one or more checking routine checking turbidity measurement result.Particularly, according to an embodiment, should be marked as suspection to all number percent turbidities of being lower than a predetermined amount.In one embodiment, predetermined amount can be-5.0%, although also can use other value.

In addition, in using the definite process of least square, also can be determined a slope error value according to known certain methods with reference to slope.According to this slope error,, a turbidity error amount determines this turbidity error amount by being multiply by a predetermined value.For example, according to an embodiment, the predetermined factor can be 1000.According to another embodiment of the invention, this factor can be 100.If this turbidity error amount surpasses a predetermined value, so number percent turbidity measurement result is labeled as suspection.The predetermined value that for example is used for the turbidity error can be 2%.

In addition, that can be marked as the number percent turbidity measurement result on a certain haze levels suspection or abandon.For example, can determine: the measurement result greater than about 50% turbidity should be dropped, because so the turbidity of a large amount can not accurately be read probably, may show it is photoresistance plug or the another kind of temporary transient problem that does not reflect the turbidity of exhaust plume on the contrary.The value that other is predetermined, for example 70%, 80%, 90% or 100%, also can be used.

In the situation of the vehicle of diesel, most preferred verification method is, the measurement result of the turbidity measurement result of getting at synchronization with the CO that got compared, because exist a association between the exhaust turbidity of CO emission and diesel vehicle.Use this method, the predetermined association between CO and the turbidity measurement result can be used for determining whether that should be considered as a concrete turbidity measurement result effectively, suspect or invalid.

Therefore, exhaust turbidity of can be on a brief time interval remotely determining a vehicle in moving according to equipment of the present invention.In addition because many existing emission surveillance equipments are used for other purpose to a reference channel, so one can use with existing systems according to equipment of the present invention, measure so that turbidity to be provided.According to an embodiment, data handling system 100 is used with existing system, allow an existing emission-monitoring system also to monitor turbidity, therefore substituting expense can minimize.

For those skilled in the art, by investigating instructions of the present invention disclosed herein and giving practice, other embodiments of the invention and use will become fairly obvious.Only should be shown instructions and example exemplary.The only appended from here claim of scope of the present invention is limited.

Claims

1. A remote sensing system for remotely determining the turbidity of a vehicle exhaust plume comprising:

a radiation source configured to transmit radiation through the exhaust plume of a motor vehicle;

One or more detectors configured to receive radiation after it has passed through the exhaust plume of a motor vehicle and to generate at least one signal indicative of at least two signals received at the one or more detectors Intensity of radiation in different detection bands;

a first of the above detection bands is selected to include a wavelength at which a gaseous component of the vehicle exhaust plume absorbs radiation significantly; and a second of the above detection bands is selected to include a wavelength at which radiation is substantially non-absorbing to a gaseous component of the vehicle exhaust plume; and

a processor programmed to determine, based on at least one signal generated by one or more detectors, the intensity of radiation provided by the radiation source in at least two different detection bands The difference in intensity between the intensities of radiation received by the one or more detectors in and based at least in part on the determined difference in intensity in the second detection band, ignoring at least for Radiation intensity measurements in a first detection band of the aforementioned detection bands for a component of .

2. The system of claim 1, wherein the processor compares the difference in intensity in the second detection band to the difference in intensity in the first detection band to determine exhaust turbidity.

3. The system of claim 2, wherein the intensity measurement of one or more gas constituents for the vehicle exhaust plume is flagged as suspect when exhaust turbidity exceeds a first predetermined level, and when the exhaust Intensity measurements for one or more gas components of the vehicle exhaust plume are flagged as discarded when the turbidity exceeds a second predetermined level.

4. The system of claim 2, wherein the percent turbidity is determined from a ratio of the difference in intensity in the second detection band to the difference in intensity in the first detection band.

5. The system of claim 1, wherein the second detection wavelength band includes a wavelength in the range of about 0.3 microns to about 1.5 microns.

6. The system of claim 5, further comprising means for isolating the radiation source from ambient environmental conditions to minimize temperature changes in the radiation source.

7. A remote sensing system for remotely determining exhaust plume turbidity of a diesel powered vehicle comprising:

a first of said detection bands is selected to include a radiation wavelength at which carbon monoxide absorbs radiation significantly; and a second of said detection bands is selected to include a radiation wavelength, At this wavelength of radiation, a gaseous component of the vehicle exhaust plume has substantially no absorption of radiation; and

a processor programmed to determine, based on at least one signal generated by one or more detectors, the intensity of radiation provided by the radiation source in at least two different detection bands relative to the intensity in the at least two detection bands an intensity difference between intensities of radiation received by the one or more detectors, and based at least in part on the determined intensity difference in the first detection band, ignoring the aforementioned detection band for vehicle exhaust turbidity Radiation intensity measurements in the second detection band.

8. The system of claim 7, wherein the exhaust turbidity is discarded based on a change in a predetermined correlation between the determined intensity difference in the first detection band and the determined intensity difference in the second detection band measurement results.

9. The system of claim 8, wherein the one or more detectors generate at least one signal indicative of the intensity of radiation received at the one or more detectors in at least three different detection wavelength bands;

the third detection band includes a wavelength of radiation absorbed by carbon dioxide; and

Wherein, the processor compares the intensity difference in the third detection band with the intensity difference in the second detection band to determine the exhaust turbidity.

10. The system of claim 9, wherein the intensity measurement of one or more gas constituents for the vehicle exhaust plume is flagged as suspect when the exhaust gas turbidity exceeds a first predetermined level, and when the exhaust gas plume An intensity measurement of one or more gas constituents for the vehicle exhaust plume is flagged as discarded when the gas turbidity exceeds a second predetermined level.

11. The system of claim 9, wherein the percent turbidity is determined from a ratio of the intensity difference in the third detection band to the intensity difference in the second detection band.

12. The system of claim 8, wherein the second detection wavelength band includes a wavelength in the range of about 0.3 microns to about 1.5 microns.

13. The system of claim 12 further comprising means for isolating the radiation source from ambient environmental conditions to minimize temperature variations of the radiation source.

14. A method for remotely sensing exhaust emissions to determine the turbidity of a motor vehicle exhaust plume comprising the steps of:

a) passing radiation from a radiation source through the exhaust plume of a motor vehicle;

b) receiving radiation at one or more detectors after the radiation has passed through the exhaust plume of the motor vehicle;

c) generating at least one first signal indicative of the intensity of radiation received at one or more detectors in a first detection wavelength band comprising a wavelength at which the row a gaseous component of the plume substantially absorbs the radiation; and generating a second signal indicative of the intensity of the radiation received at the one or more detectors in a second detection wavelength band, the first 2. The detection band includes a wavelength at which radiation is substantially non-absorbing by a gaseous component of the vehicle exhaust plume;

d) from the generated first and second signals, determining an intensity difference between the intensity of the radiation source and the intensity of radiation received at the one or more detectors in the first and second detection bands;

e) comparing the above-determined intensity difference in the first and second detection bands to obtain a measure of exhaust turbidity; and

f) if the exhaust turbidity exceeds a predetermined threshold level, then discard the above-mentioned radiation intensity measurements in the first detection band;

15. The method of claim 14, further comprising the step of:

g) Repeat steps a to f until the exhaust gas turbidity no longer exceeds the predetermined threshold level.

16. The method of claim 15, further comprising the step of:

h) determining the concentration of at least one gaseous component of the vehicle exhaust plume from the determined intensity difference in at least one detection band comprising a wavelength at which the gaseous component of the exhaust plume Significant absorption of radiation;

17. The method of claim 16, wherein the first detection wavelength band includes a wavelength at which carbon dioxide absorbs radiation significantly;

18. The method of claim 17 for determining exhaust opacity of a diesel powered vehicle, further comprising the step of:

generating a third signal indicative of the intensity of radiation received at the one or more detectors in a third detection wavelength band; the third detection wavelength band includes a wavelength at which carbon monoxide reacts to radiation have significant absorption;

from the generated third signal, determining an intensity difference between an intensity of source radiation and an intensity of radiation received at the one or more detectors in a third detection wavelength band;

The exhaust gas turbidity is verified by comparing the determined intensity difference in the third detection band with a predetermined correlation between the exhaust gas turbidity and the carbon monoxide concentration.

19. The method of claim 17, wherein the second detection wavelength band includes a wavelength in the range from about 0.3 microns to about 1.5 microns.

20. A method for remotely sensing exhaust emissions to determine exhaust plume turbidity of a diesel powered vehicle comprising the steps of:

b) receiving the radiation at one or more detectors after the radiation has passed through the motor vehicle exhaust plume;

c) generating at least one first signal indicative of the intensity of radiation received at the one or more detectors in a first detection wavelength band comprising a wavelength at which, carbon monoxide absorbs radiation significantly; and generating a second signal indicative of the intensity of the radiation received at the one or more detectors in a second detection band comprising a wavelength at At this wavelength, a gaseous component of the vehicle exhaust plume has substantially no absorption of radiation;

e) determining exhaust turbidity from said intensity difference in said second detection band;

f) if the intensity difference in the first detection band does not fall into a predetermined correlation with the exhaust turbidity, discarding the determined exhaust turbidity;

21. The method of claim 20, wherein the second detection wavelength band includes a wavelength in the range from about 0.3 microns to about 1.5 microns.