Abstract: A sensor for mixing ratio of liquid fuel comprising: a cylindrical enclosure having both inlet and outlet opening to act as a passage through which a mixing liquid fuel flows; a transparent column concentrically disposed into the enclosure to make outer surface contact with the liquid fuel; light emitting diode and photo diode each provided so as to sandwich the column in the lengthwise direction, so that the light emitted from the former enters the column through its one end and reflects at the boundary of the column and the liquid fuel, and go out of the other end thereof to fall on the latter; a temperature compensation photo diode disposed in the enclosure with the light of the light emitting diode partly as a light source to rectify the characteristics influenced under the ambient temperature variation; a voltage control circuit provided to control the voltage across the light emitting diode so as to maintain uniform output from the temperature compensation photo diode.

Abstract: A sensor for mixing ratio of gasoline and alcohol comprising: a transparent column, both ends of which are supported by grips; the surface of the column is positioned in direct contact with a mixing liquid of gasoline and alcohol; a light emitting diode disposed so that light beams therefrom are incident on one end of said transparent column and the mixing liquid, said beams incident on said boundary at less than a critical angle being totally refracted, while said beams incident on said boundary at more than the critical angle being totally reflected to pass within said column so as to go out from the other end thereof, said critical angle depending upon a mixing degree of said liquid; a photo diode placed to receive the light beams reflected from the boundary so as to generate an output in accordance with the quantity of the light beams received; and the column being substantially determined its lengthwise and diametrical dimension such that the light beams incident upon the boundary at a critical angle, ar

Abstract: An air/fuel ratio sensor having an unambiguous output with respect to both the fuel-rich and the fuel-lean regions and which does not require the introduction of atmospheric air. The sensor is composed of first and second elements, each having porous electrodes formed on opposite sides of an oxygen-ion-conductive electrolyte plate. The two elements are arranged to define between them a gas compartment communicating with the atmosphere to be detected via one or more diffusion limiting portions. One of the elements serves as an oxygen concentration differential electrochemical cell and the other one as an oxygen pump. An internal reference oxygen source is formed on the side of one of the elements opposite the gas compartment, and a small current is caused to flow the first element so as to transfer oxygens from the gas compartment to the oxygen source.