LIQUID LEVEL SENSOR HAVING AN INTEGRAL PTC AND NTC THERMISTOR

摘要

An integral thermally responsive resistor device for liquid level sensing applications. A barium titanate first body member having a positive temperature coefficient of resistance is in intimate thermal association and in parallel electrically with a second body member of negative temperature coefficient material. The resistivity of the barium titanate dominates total device resistance for self-heating at low temperatures, while the resistivity of the negative temperature coefficient material dominates total device resistance at higher temperatures. In a preferred embodiment, the barium titanate is a cylindrical core which has a tubular outer sleeve of iron vanadium borophosphate glass. Two spaced electrodes electrically connect the core and outer sleeve in parallel and provide electrical interconnection means to a liquid level sensing circuit.