| 摘要 |
A sensor for detecting whether liquid is present at a location in a tank, comprises a probe placed at the location, containing a negative temperature coefficient resistor (NTC) and a positive temperature coefficient resistor (PTC) mutually connected in series relation. The positive temperature coefficient resistor exhibits a progressive resistance variation responsive to temperature change. An electrical power source delivers a constant electric current to the probe. The detector further comprises a comparator for comparing the total resistance of the serially mounted resistors with a threshold.
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