Solid state mass air flow sensor
Patent 4487063 Issued on December 11, 1984. Estimated Expiration Date: 
July 11, 2003. Estimated Expiration Date is calculated based on simple USPTO term provisions. It does not account for terminal disclaimers, term adjustments, failure to pay maintenance fees, or other factors which might affect the term of a patent.
July 11, 2003. Estimated Expiration Date is calculated based on simple USPTO term provisions. It does not account for terminal disclaimers, term adjustments, failure to pay maintenance fees, or other factors which might affect the term of a patent.Patent ReferencesDevice for measuring and/or monitoring the flow velocity of a flowing fluid Solid state fluid flow sensor Patent #: 3992940 InventorAssigneeApplicationNo. 06/512551 filed on 07/11/1983US Classes:73/204.19, For temperature374/114, By current modifying elements in circuit (e.g., bridge)73/204.23Having particular electrical heating, cooling, or thermal sensing elementExaminersPrimary: Goldstein, HerbertAttorney, Agent or FirmInternational ClassesG01F 1/698 (20060101)G01F 1/696 (20060101) AbstractA hot element anemometer uses solid state diode chips for the heated air flow sensing element and the ambient temperature sensing element in parallel circuit branches. The air flow sensing element carries a heating resistor on the diode chip. Constant current sources of equal value supply current through the diodes. The air flow sensor diode is in series with a resistor which determines the nominal temperature difference between the diode chips. A circuit compares voltages in the two diode branches and provides an air flow output signal and controls the temperature of the air flow sensor diode. To compensate for changes of thermal conductivity of the air temperature and various temperature effects in the circuit, a third current source is coupled to the ambient temperature sensing branch through a resistor network and includes resistors that can be adjusted to provide a functional calibration which yields an air flow signal free of linear temperature effects.Other References
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