Gm Global Technolgoy Operations, Inc.

Michael James O'Rourke

Michel Farid Sultan

Charles Robert Harrington

Antonio B Catalan

Joseph L Kenty

A low cost, bi-directional manifold air flow sensing device based on sensed temperature differential due to airflow achieves improved sensitivity and frequency response by eliminating the heater element of the conventional sensor topology, and operating the sensor elements at a relatively higher current so that each temperature sensing element heats both itself and the other temperature sensing element. The sensitivity is significantly increased due to the increased current in the sensor elements, and the frequency response is significantly increased due to closer spacing of the sensor elements. With this new topology, the sensor elements are said to be mutually heated. In a particularly advantageous mechanization, the sensing device includes two separate pairs of upstream and downstream sensing elements, and the sensing elements are connected in the four legs of a Wheatstone bridge. The sensitivity is doubled since sensor elements are connected in each of the bridge legs, and performance and cost are improved through the elimination of off-chip bridge components. A simple, low cost, temperature compensation circuit compensates for ambient temperature variations.

Bi-directional mass air flow sensor having mutually-heated sensor

A temperature sensor apparatus comprising: a capacitor with first and second conductors and a dielectric material between the conductors; a frequency generator coupled to the capacitor and providing an excitation signal thereto; a processor coupled to the capacitor, wherein the processor monitors a capacitance of the capacitor, converts the capacitance to a temperature signal, and alters a frequency of the excitation signal when the temperature signal passes a predetermined threshold.

Temperature sensor

A temperature sensor comprising: a wave guide with a cylindrical wall; a material of low emissivity included at the cylindrical wall for generating black body radiation into the wave guide, wherein at least a portion of the generated black body radiation is carried through the wave guide; a first sensor receiving the generated black body radiation and providing a first output signal indicative of a first magnitude of a first bandwidth of the generated black body radiation; and a second sensor receiving the generated black body radiation and providing a second output signal indicative of a second magnitude of a second bandwidth of the generated black body radiation, wherein a difference between the first and second output signals is a linearized indication of temperature of at least a portion of the wave guide.

The present invention is directed to a single solid state thermal diffusion sensor capable of measuring both the composition and flow of gaseous vapors traveling through a duct. The sensor comprises two orthogonal sensing patterns, each having a heating element positioned equidistant between two thermistor elements. The heaters and thermistors are made from thin film platinum deposited on a thermally insulating polyimide layer having low thermal diffusivity. A sinusoidal voltage is applied to each heating element for generating oscillating thermal waves which propagate through the gaseous vapor to their respective thermistors. The thermistors of a first, transversely positioned sensing pattern are responsive to both the composition and flow of the gaseous vapor, while the thermistors of a second, longitudinally positioned sensing pattern are responsive only to the composition of the gaseous vapor. Appropriate electronic circuitry utilizes the responses of the thermistor pairs for determining the composition and flow of the gaseous vapor.

Vapor composition and flow sensor

A gas vapor sensor indicates the relative concentrations and flow rate of a gas mixture. Acoustic noise is generated within a closed chamber by the gas mixture flowing therethrough or by ambient noise sources. The chamber has a fundamental resonant frequency which varies with the vapor concentration. Acoustic frequency components of the noise corresponding to the resonant frequency of the chamber are sharply reinforced and dominate the acoustic spectrum within the chamber. The spectrum is detected and frequency filtered by a pair of dissimilar parallel filters to produce two attenuated outputs. The difference between the attenuated outputs indicates the resonant frequency and is a measure of the vapor concentration. The strength of the acoustic spectrum together with the measured vapor concentration indicates the flow rate of the mixture.

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Warren, MI, United States of America

Michael James O'Rourke