Technology Corporation

James H Trageser

A method and apparatus are disclosed for obtaining a very accurate mass flow rate for a fluid flowing in a conduit in accordance with the principles of King's Law. A single temperature sensitive resistive element is disposed within the fluid flow path. The temperature sensitive resistive element constitutes one leg of a resistor bridge across which the inputs of a differential amplifier are disposed. The output of the differential amplifier is employed as a feedback current source to the bridge in order to maintain the temperature sensitive resistive element at a constant temperature in the self-heating mode. Another leg of the bridge is rapidly switched back and forth before two different resistances such that the temperature sensitive resistive element correspondingly alternates between two different 'constant' temperatures. The two voltage drops necessary to maintain the temperature sensitive resistive element at its corresponding two 'constant' temperatures are repeatedly sampled, and calculations are performed to convert this information into power dissipation information by which King's Law may be applied to obtain mass flow rate and, if desired, the ambient temperature of the fluid flowing with the conduit.

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Dayton, OH, United States of America

James H Trageser