Abstract: A liquid sensing apparatus for a fuel tank comprises a first optical sensor for producing an output having a first state that corresponds to the first optical sensor being exposed to air and a second state that corresponds to the first optical sensor being exposed to fuel; and a circuit for detecting the first and second optical sensor output states. The sensor circuit also has self test capability for testing both active and passive components. The sensor circuits can be accessed using a two wire only interface, and thermal stability can be achieved with the electronic circuit as shown.

Abstract: A liquid sensing apparatus for a fuel tank comprises a first optical sensor for producing an output having a first state that corresponds to the first optical sensor being exposed to air and a second state that corresponds to the first optical sensor being exposed to fuel; a second optical sensor for producing an output having a first state that corresponds to the second optical sensor being exposed to air or water, and a second state that corresponds to the second optical sensor being exposed to fuel; and a circuit for detecting the first and second optical sensor output states. The sensor circuits can be accessed using a two wire only interface, and thermal stability can be achieved with the electronic circuit as shown.

Abstract: An apparatus and method for measuring the torque of a rotating shaft is provided, utilizing a single sensor which provides a signal which is processed to yield a temperature compensated value of the torque applied to a rotating shaft. A magneto-optic material such as a Faraday film is positioned adjacent to the rotating shaft and is subjected to a saturating magnetic field. Ferrous elements are provided about the periphery of the rotating shaft and cause the modulation of the magnetic field applied to the magneto-optic material. The rotation of the linear polarization vector of light passing through the magneto-optic material when the material is magnetized to the saturation level changes in accordance with temperature. Thus, the amplitude of the output optical signal varies in accordance with the temperature of the shaft.

Abstract: A displacement detector provides a light beam which impinges on an article with different combinations of light altering materials such as reflecting and non-reflecting surfaces, wave retarding plates, and linear polarizers attached to the article to determine angular position, relative angular displacement, and speed of rotatably mounted articles. These beam altering materials change either the polarization state or the magnitude of the light in a predictable manner. When used on different ends of a rotating shaft, the shaft speed and torsional displacement of the front shaft end with respect to the rear shaft end can be determined. When used with an article such as a rotatably mounted throttle, the angular displacement of the throttle can be determined.