Importance

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Abstract

This invention generally pertains to a device for electrically detecting a liquid level such as water, oil and so on, which is suitably used for an automatic operating apparatus for a pump, or for a liquid level warning device. The device of the invention comprises an electric heater disposed flush with a liquid level to be detected, a heater temperature detector to electrically detect a heater temperature to generate a heater temperature signal, and an environment temperature detector to electrically detect an environment temperature to generate an environment temperature signal. In one aspect of the invention, there is further provided a reference signal generator to generate a reference signal depending on the range of the environment temperatures at which the liquid level is to be detected, and a comparative circuit to electrically compare a difference between the heater temperature signal and the environment temperature signal to generate a level signal. In another aspect of the invention, there is provided a comparative circuit to electrically compare a ratio of said heater temperature signal to said environment temperature signal with a reference ratio depending on the range of the environment temperatures at which said liquid level is to be detected to generate a level signal.

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First Claim