Sensor for measuring alcohol content of alcohol gasoline fuel mixtures

Claim 1

A sensing device for determining the alcohol content of an alcohol/gasoline fuel mixture during the operation of an engine, said sensing device comprising: a light source emitting a light beam containing at least a first and a second wavelength within the near-infrared spectrum, said light beam being continuously transmitted at a substantially constant intensity through the alcohol/gasoline fuel mixture during the operation of the engine; first and second detectors which are disposed so as to continuously receive said light beam after its transmission through the alcohol/gasoline fuel mixture, said first detector producing an output corresponding to a first amount of absorption by the alcohol/gasoline fuel mixture at said first wavelength, and said second detector producing an output corresponding to a second amount of absorption by the alcohol/gasoline fuel mixture at said second wavelength; detector means disposed adjacent said first and second detectors so as to continuously produce an output corresponding to a drift in ambient temperature of said first and second detectors, said detector means being shielded from said light source to substantially prevent said detector means from receiving said light beam; means for measuring said outputs from said first and second detectors and said detector means; and computational means for determining, from said outputs, the difference between said outputs of said first detector and said detector means and the difference between said outputs of said second detector and said detector means, the ratio of said differences being a ratio of said first and second absorbances by the alcohol/gasoline fuel mixture at said first and said second wavelengths, such that said ratio of absorbances provides an output indicative of the alcohol content within the alcohol/gasoline mixture during the operation of the engine.

Claim 18

A method for determining the alcohol content of an alcohol/gasoline mixture containing up to about 85% by volume of alcohol, which is provided via a fuel carrying line to an internal combustion engine for operation of that engine, comprising the following steps: continuously emitting a light beam at a substantially constant intensity from a light source during the operation of the engine, said light beam containing at least a first and a second wavelength within the near-infrared spectrum, wherein at said first wavelength, the alcohol is significantly more absorbing than the gasoline component of the mixture and at said second wavelength, the alcohol and gasoline components are both essentially non-absorbing, said light beam being transmitted through the alcohol/gasoline mixture over a single optical path of predetermined length through the fuel carrying line; continuously detecting at a first and second detector said emitted light beam after transmission through the alcohol/gasoline mixture within the fuel carrying line, said first detector being optically filtered to receive a spectral band of wavelengths centered about said first wavelength so as to determine a first amount of absorbance by the alcohol/gasoline mixture at said first wavelength, and said second detector being optically filtered to receive a spectral band of wavelengths centered about said second wavelength which does not overlap said band centered around said first wavelength so as to determine a second amount of absorbance by the alcohol/gasoline mixture at said second wavelength, said first and second detectors each generating an output voltage proportional to the sum of the incident light it receives at each of said wavelengths and an ambient temperature; continuously detecting said ambient temperature with a third and fourth thermopile-type detectors disposed adjacent to said first and second detectors such that each said third and fourth thermopile-type detectors produces an output voltage corresponding to a drift in said ambient temperature of a corresponding one of said first and second detectors, said third and fourth detector being shielded by opaque screens from said light source to substantially prevent said third and fourth detectors from receiving said light beam, said third detector corresponding to said first detector and said fourth detector corresponding to said second detector; measuring said output voltage from each of said first, second, third and fourth detectors; and computing from said output voltages, the difference between said output voltages of said first and third detectors and the difference between said output voltages of said second and fourth detectors, the ratio of said differences being a ratio of said first and second absorbances by the alcohol/gasoline fuel mixture at said first and said second wavelength, wherein said ratio (R) is equal to (V 1 -V 3 )/(V 2 -V 4 ), with V 1 and V 2 being said output voltages by said first and second detectors sensing at said first and second wavelengths, respectively, and V 3 and V 4 being said output voltages by said third and fourth detectors sensing said drift in said ambient temperature; such that said ratio of absorbances is indicative of the alcohol content within the alcohol/gasoline mixture.

Claim 19

A method for determining the alcohol content of an alcohol/gasoline mixture containing up to about 85% by volume of alcohol, which is provided via a fuel carrying line to an internal combustion engine for operation of that engine, comprising the following steps: continuously emitting a light beam at a substantially constant intensity from a light source during the operation of the engine, said light beam containing at least a first and a second wavelength within the near-infrared spectrum, wherein at said first wavelength, the alcohol is significantly more absorbing than the gasoline component of the mixture and at said second wavelength, the alcohol and gasoline components are both essentially non-absorbing, said light beam being transmitted through the alcohol/gasoline mixture over a single optical path of predetermined length through the fuel carrying line; continuously detecting at a first and second detector said emitted light beam after transmission through the alcohol/gasoline mixture within the fuel carrying line, said first detector being optically filtered to receive a spectral band of wavelengths centered about said first wavelength so as to determine a first amount of absorbance by the alcohol/gasoline mixture at said first wavelength, and said second detector being optically filtered to receive a spectral band of wavelengths centered about said second wavelength which does not overlap said band centered around said first wavelength so as to determine a second amount of absorbance by the alcohol/gasoline mixture at said second wavelength, said first and second detectors each generating an output voltage proportional to the sum of the incident light it receives at each of said wavelengths and an ambient temperature; continuously detecting said ambient temperature with a third and fourth thermopile-type detectors disposed adjacent to said first and second detectors such that each said third and fourth thermopile-type detectors produces an output voltage corresponding to a drift in said ambient temperature of a corresponding one of said first and second detectors, said third and fourth detector being shielded by opaque screens from said light source to substantially prevent said third and fourth detectors from receiving said light beam, said third detector corresponding to said first detector and said fourth detector corresponding to said second detector; measuring said output voltage from each of said first, second, third and fourth detectors; and computing from said output voltages, the difference between said output voltages of said first and third detectors and the difference between said output voltages of said second and fourth detectors, the ratio of said differences being a ratio of said first and second absorbances by the alcohol/gasoline fuel mixture at said first and said second wavelength, wherein said ratio (R) is equal to (V 1 -V 3 )/(V 2 -V 4 ), with V 1 and V 2 being said output voltages by said first and second detectors sensing at said first and second wavelengths, respectively, and V 3 and V 4 being said output voltages by said third and fourth detectors sensing said drift in said ambient temperature; such that said ratio of absorbances is indicative of the alcohol content within the alcohol/gasoline mixture.