System and method for remote emissions sensing including calculation and calibration techniques compensating for temperature and pressure effects
First Claim
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1. A method of correcting for an effect of temperature and pressure on one or more exhaust gas constituents of an exhaust plume, in a measurement path, emitted from a motor vehicle during an emissions test, the method comprising:
- measuring ambient temperature and ambient pressure at a vehicle emissions test site;
measuring, from an exhaust plume of a passing motor vehicle, an amount of a selected gas constituent present in the exhaust plume in the measurement path;
generating, for the selected gas constituent, a temperature correction value based, in part, on the measured ambient temperature, wherein the temperature correction value is determined from a temperature correction proportionality coefficient that is defined by a temperature correction curve polynomial function that describes the temperature correction proportionality coefficient as a function of the measured amount of the selected gas constituent, and wherein the step of generating the temperature correction value comprises;
(i) determining the temperature correction proportionality coefficient as a function of the measured amount of the selected gas constituent according to the temperature correction polynomial function; and
(ii) generating the temperature correction value by multiplying the temperature correction proportionality coefficient by the temperature difference between a base temperature and the measured ambient temperature;
generating, for the selected gas constituent, a pressure correction value based, in part, on the measured ambient pressure, wherein the pressure correction value is determined from a pressure correction proportionality coefficient that is defined by a pressure correction curve polynomial function that describes the pressure correction proportionality coefficient as a function of the measured amount of the selected gas constituent, and wherein the step of generating the pressure correction value comprises;
(i) determining the pressure correction proportionality coefficient as a function of the measured amount of the selected gas constituent according to the pressure correction polynomial function; and
(ii) generating the pressure correction value by multiplying the pressure correction proportionality coefficient by the pressure difference between a base pressure and the measured ambient pressure;
applying the temperature correction value and the pressure correction value to the measured amount of the selected gas constituent to generate a corrected gas amount for the selected gas constituent; and
storing the corrected gas amount generated for the selected gas constituent in a memory.
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Abstract
A remote emissions sensing (RES) system and method for measuring the exhaust gas composition of a motor vehicle is provided, including calibration methodologies for compensating for the effects of ambient temperature and/or pressure.
59 Citations
6 Claims
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1. A method of correcting for an effect of temperature and pressure on one or more exhaust gas constituents of an exhaust plume, in a measurement path, emitted from a motor vehicle during an emissions test, the method comprising:
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measuring ambient temperature and ambient pressure at a vehicle emissions test site; measuring, from an exhaust plume of a passing motor vehicle, an amount of a selected gas constituent present in the exhaust plume in the measurement path; generating, for the selected gas constituent, a temperature correction value based, in part, on the measured ambient temperature, wherein the temperature correction value is determined from a temperature correction proportionality coefficient that is defined by a temperature correction curve polynomial function that describes the temperature correction proportionality coefficient as a function of the measured amount of the selected gas constituent, and wherein the step of generating the temperature correction value comprises; (i) determining the temperature correction proportionality coefficient as a function of the measured amount of the selected gas constituent according to the temperature correction polynomial function; and (ii) generating the temperature correction value by multiplying the temperature correction proportionality coefficient by the temperature difference between a base temperature and the measured ambient temperature; generating, for the selected gas constituent, a pressure correction value based, in part, on the measured ambient pressure, wherein the pressure correction value is determined from a pressure correction proportionality coefficient that is defined by a pressure correction curve polynomial function that describes the pressure correction proportionality coefficient as a function of the measured amount of the selected gas constituent, and wherein the step of generating the pressure correction value comprises; (i) determining the pressure correction proportionality coefficient as a function of the measured amount of the selected gas constituent according to the pressure correction polynomial function; and (ii) generating the pressure correction value by multiplying the pressure correction proportionality coefficient by the pressure difference between a base pressure and the measured ambient pressure; applying the temperature correction value and the pressure correction value to the measured amount of the selected gas constituent to generate a corrected gas amount for the selected gas constituent; and storing the corrected gas amount generated for the selected gas constituent in a memory. - View Dependent Claims (2, 3, 4, 5)
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6. A system for correcting for an effect of temperature and pressure on one or more exhaust gas constituents of an exhaust plume, in a measurement path, emitted from a motor vehicle during an emissions test, comprising:
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means for measuring ambient temperature and ambient pressure at a vehicle emissions test site; means for measuring, from an exhaust plume of a passing motor vehicle, an amount of a selected gas constituent present in the exhaust plume in the measurement path; means for generating, for the selected gas constituent, a temperature correction value based, in part, on the measured ambient temperature, wherein the temperature correction value is determined from a temperature correction proportionality coefficient that is defined by a temperature correction curve polynomial function that describes the temperature correction proportionality coefficient as a function of the measured amount of the selected gas constituent, and wherein generating the temperature correction value comprises; (i) determining the temperature correction proportionality coefficient as a function of the measured amount of the selected gas constituent according to the temperature correction polynomial function; and (ii) generating the temperature correction value by multiplying the temperature correction proportionality coefficient by the temperature difference between a base temperature and the measured ambient temperature; means for generating, for the selected gas constituent, a pressure correction value based, in part, on the measured ambient pressure, wherein the pressure correction value is determined from a pressure correction proportionality coefficient that is defined by a pressure correction curve polynomial function that describes the pressure correction proportionality coefficient as a function of the measured amount of the selected gas constituent, and wherein generating the pressure correction value comprises; (i) determining the pressure correction proportionality coefficient as a function of the measured amount of the selected gas constituent according to the pressure correction polynomial function; and (ii) generating the pressure correction value by multiplying the pressure correction proportionality coefficient by the pressure difference between a base pressure and the measured ambient pressure; means for applying the temperature correction value and the pressure correction value to the measured amount of the selected gas constituent to generate a corrected gas amount for the selected gas constituent; and means for storing the corrected gas amount generated for the selected gas constituent for further processing.
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Specification