VEHICLE EXHAUST EMISSIONS ANALYZER

• US 3,696,247 A
• Filed: 11/12/1970
• Issued: 10/03/1972
• Est. Priority Date: 11/12/1970
• Status: Expired due to Term

• Current Assignee: Daniel E. Weber, Lionel D. Mcintosh
• Original Assignee: Daniel E. Weber, Lionel D. Mcintosh
• Inventors: McIntosh, Lionel D., Weber, Daniel E.
• Primary Examiner(s): Wibert, Ronald L.
• Assistant Examiner(s): Evans, F. L.
• Application Number:
  US05/088,784
• Time in Patent Office: 691 Days
• Field of Search: 250/43.5R,83.3H,218,226 356/74,81,88-101,51
• US Class Current: 250/339.07
• CPC Class Codes: F02D 41/1451 the sensor being an optical sensor
• CPC Class Codes: G01J 3/36 Investigating two or more bands of a spectrum by separate detectors
• CPC Class Codes: G01J 3/42 Absorption spectrometry; Double beam spectrometry; Flicker spectrometry; Reflection spectrometry beam switching arrangements G01J3/08
• CPC Class Codes: G01N 21/3504 for analysing gases, e.g. multi-gas analysis

Abstract

An infrared absorption analyzer for measuring the concentration of CO, CO2, H-C and NO in a stream of vehicle exhaust emissions passing through the same sampling cell. The analyzer employs a single source of infrared radiation and a double beam optical comparator system, which is common to and shared by all of the measuring channels, and a dispersive type spectrophotometer, which has a plurality of exit slits and a single entrance slit through which it is alternately excited by respective ones of the beams, one of which passes through the sampling analytical cell.

Claims

2. Analyzer apparatus in accordance with claim 1 wherein said means for alternately presenting includes a chopper device located in the path of both of said beams and operable to interrupt the transmission of one of said beams to said entrance slit when the other beam is being transmitted thereto and a focusing member common to and located in the path of both of said beams between said chopper device and said entrance slit for directing the chopped beams along the same path through said entrance slit into said spectrometer.

3. Analyzer apparatus in accordance with claim 1 wherein each of said signal processing channels includes a synchronous balanced demodulator having a pair of opposite polarity field effect transistors in the respective demodulation branches thereof and a synchronous switching circuit operated from and in synchronism with said chopper device and connected to the field effect transistors in the demodulator of each signal processing channel.

4. An absorption type, dispersive infrared analyzer apparatus for analysis of vehicle exhaust gas emissions including CO, CO2, HC and NO, said analyzer apparatus comprising, in combination, a source of infrared radiation, means deriving a reference beam and a sampling beam from radiation received from said source and directing said beams along two different paths, a single sampling cell having an inlet adapted to be connected to the vehicle exhaust and an outlet in communication with the atmosphere, said cell located in the path of said sampling beam for selective absorption of a portion of the radiation directed therethrough by the aforementioned components of the vehicle exhaust gases in accordance with the concentration thereof passing through the cell, a spectrometer having an entrance slit, means for dispersing radiation entering said slit into spectral lines of the infrared spectrum, and a plurality of exit slits spaced to pass the dispersed radiation in selected bands of the infrared spectrum identified with the aforementioned components of the exhaust gas, means located in the path of the reference beam and the sampling beam for directing the reference beam and the sampling beam alternately into said spectrometer through said entrance slit, a plurality of infrared detectors each positioned behind a different one of said exit slits and providing an electrical signal corresponding to the intensity of the radiation passing through its associated slit, a plurality of signal processing channels each connected to a different one of said detectors and providing a signal output therefrom corresponding to thE difference in intensity between the reference beam and sampling beam passing through the exit slit for the detector corresponding to that channel, and signal utilization means connected to receive the output signal from respective ones of said channels.

5. Analyzer apparatus in accordance with claim 4 wherein said means for directing the reference beam and sampling beam alternately into said spectrometer includes chopper means located in the path of both said beams and operated to interrupt transmission of one beam to said entrance slit when the other beam is being transmitted therethrough and a focusing mirror common to and located in the path of both said beams between the chopper means and said entrance slit for directing the chopped reference beam and the chopped sampling beam along the same path through said entrance slit into said spectrometer.

6. Analyzer apparatus in accordance with claim 5 further including a plane mirror in the path of said reference beam and wherein said chopper means has a mirrored surface on one side thereof facing said plane mirror to reflect the reference beam upon said focusing mirror.

7. Analyzer apparatus in accordance with claim 6 including an adjustable iris diaphragm member in the path of the reference beam to adjust the intensity thereof relative to the sampling beam and compensate for any difference in the optical path lengths thereof.

8. Analyzer apparatus in accordance with claim 5 wherein the only moving part of the optical apparatus is said chopper means.

9. Analyzer apparatus in accordance with claim 5 wherein each of said signal processing channels comprises a balanced demodulator having a pair of opposite polarity field effect transistors therein and includes a synchronous switching circuit operated from and in synchronism with said chopper means and connected to the field effect transistors of each demodulator in each signal processing channel.

10. Analyzer apparatus in accordance with claim 5 wherein said sampling cell is of an optimized length for CO, CO2, H-C and NO gases and wherein the CO2 exit slit of said spectrometer is tuned to the carbon 13 isotope to prevent saturation of the CO2 measuring channel due to the optimized sampling cell common to each measuring channel.

11. Analyzer apparatus in accordance with claim 5 wherein said spectrometer includes a cell filter between the exit slit and the detector device of the CO2 channel thereof to prevent optical cross talk between the CO and the CO2 channels.