Sensor for measuring alcohol content of alcohol/gasoline fuel mixtures

A sensing device for determining the alcohol content of an alcohol/gasoline mixture which is provided via a fuel carrying line to an internal combustion engine for operation of that engine, comprising:

• means for measuring the temperature of the alcohol/gasoline mixture..
• a current-controlled light source emitting a light beam containing at least a first and a second wavelengths within the near-infrared spectrum, said light beam being transmitted through the alcohol/gasoline mixture within the fuel carrying line;
• means for switching the current through said light source between two fixed values, so as to correspondingly switch the light intensity at said first and said second wavelengths which is emitted by said light source;
• first and second thermopile-type detectors disposed so as to receive said emitted light beam after its transmission through the alcohol/gasoline mixture within the fuel carrying line, said first detector being optically filtered to receive a 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 for each of said fixed current values, and said second detector being optically filtered to receive a band of wavelengths centered about said second wavelength which does not overlap said band centered about said first wavelength so as to determine a second amount of absorbance by the alcohol/gasoline mixture at said second wavelength for each of said fixed current values;
• means for separately measuring the output voltage from each of said first and second thermopile-type detectors for each of said fixed current values;
• and
• computational means for determining, from said output voltages, the ratio of said first and second absorbances by the alcohol/gasoline fuel mixture at said first and said second wavelengths for each of said fixed current values, wherein said ratio (R) is equal to (V.sub.1A -V.sub.1B)/(V.sub.2A -V.sub.2B), with V.sub.1A and V.sub.1B being said voltage outputs by said first detector sensing at said first wavelength corresponding to each of said fixed current values respectively, and V.sub.2A and V.sub.2B being said voltage outputs by said second detector sensing at said second wavelength corresponding to each of said fixed current values respectively;
• such that said ratio of absorbances when considered with said temperature of the mixture is indicative of said alcohol content within the alcohol/gasoline mixture.

A sensing device 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:

• means for measuring the temperature of the alcohol/gasoline mixture;
• a current-controlled light source emitting a light beam containing at least a first and a second wavelengths 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;
• means for switching the current through said light source between two fixed values, so as to correspondingly switch the light intensity at said first and said second wavelengths which is emitted by said light source;
• first and second thermopile-type detectors disposed so as to receive said emitted light beam after its 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 for each of said fixed current values, 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 for each of said fixed current values;
• means for separately measuring the output voltage from each of said first and second thermopile-type detectors for each of said fixed current values;
• and
• computational means for determining, from said output voltages, the ratio of said first and second absorbances by the alcohol/gasoline fuel mixture at said first and said second wavelengths for each of said fixed current values, wherein said ratio (R) is equal to (V.sub.1A -V.sub.1B)/(V.sub.2A -V.sub.2B), with V.sub.1A and V.sub.1B being said voltage outputs by said first detector sensing at said first wavelength corresponding to each of said fixed current values respectively, and V.sub.2A and V.sub.2B being said voltage outputs by said second detector sensing at said second wavelength corresponding to each of said fixed current values respectively;
• such that said ratio of absorbances when considered with said temperature of the mixture is indicative of said alcohol content within the alcohol/gasoline mixture.

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:

• measuring the temperature of the alcohol/gasoline mixture;
• emitting a light beam from a current-controlled light source, said light beam containing at least a first and a second wavelengths 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;
• switching the current through said light source between two fixed values, so as to correspondingly switch the light intensity at said first and said second wavelengths which is emitted by said light source;
• 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 for each of said fixed current values, 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 for each of said fixed current values, said first and second detectors each generating an output voltage proportional to the incident light it receives at each of said wavelengths for each of said fixed current values;
• separately measuring the output voltage from each of said first and second detectors for each of said fixed current values;
• and
• computing from said output voltages, the ratio of said first and second absorbances by the alcohol/gasoline fuel mixture at said first and said second wavelengths for each of said fixed current values, wherein said ratio (R) is equal to (V.sub.1A -V.sub.1B)/(V.sub.2A -V.sub.2B), with V.sub.1A and V.sub.1B being said voltage outputs by said first detector sensing at said first wavelength corresponding to each of said fixed current values respectively, and V.sub.2A and V.sub.2B being said voltage outputs by said second detector sensing at said second wavelength corresponding to each of said fixed current values respectively;
• such that said ratio of absorbances when considered with said temperature of the mixture is indicative of said alcohol content within the alcohol/gasoline mixture.