| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a liquid level sensor capable of outputting a fixed output voltage at any time even when the liquid level of a liquid under test intersects with respective sensing electrodes at any point. Ž<P>SOLUTION: The liquid level sensor is provided with a substrate 21 vertically erected, a first sensing electrode 22; a second sensing electrode 23; and a third sensing electrode 24. The first, second third sensing electrodes are arranged in this order from bottom to top. The liquid level sensor includes a fourth sensing electrode 25 for measuring the electrostatic capacity between the electrodes without being influenced by the dielectric constant of the liquid under test, and is designed to stop charging and only perform discharging when a time constant relating to the electrostatic capacity measured by the first sensing electrode 22 becomes smaller than a time constant relating to the electrostatic capacity measured by the fourth sensing electrode 25, and to stop discharging and only perform charging when a time constant relating to the electrostatic capacity measured by the third sensing electrode 24 becomes larger than the time constant relating to the electrostatic capacity measured by the fourth sensing electrode 25. Ž<P>COPYRIGHT: (C)2010,JPO&INPIT Ž
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