Importance

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Abstract

The flow monitoring device comprises a housing having a passageway therethrough for liquid flow through the housing. The passageway has an inlet opening and an outlet opening. A first thermistor is provided for sensing the temperature of the liquid in the passageway at a place near the inlet opening. A heating resistor is provided for heating the liquid at a place near the outlet opening and a second thermistor is provided for sensing the temperature of the liquid at the place near the outlet opening. A control circuit controls the input of heat energy to the heating resistor for heating the liquid just enough to maintain a predetermined temperature differential between the first and second thermistors. The passageway has a first larger-in-cross-section passageway portion at the place of the first thermistor for enhancing temperature sensing, a second larger-in-cross-section passageway portion at the place of the second thermistor for enhancing temperature sensing and a smaller-in-cross-section passage between the first and second larger passageway portions to cause a higher flow rate between those portions to thermally isolate those portions thereby to minimize, if not altogether eliminate, thermal pollution between those portions. The first and second passageway portions gradually widen from their inlet and outlet ends to the larger-in-cross-section portions to minimize turbulent flow through said first and second portions.

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First Claim