| 摘要 |
PROBLEM TO BE SOLVED: To provide a liquid level detector capable of accurately detecting the liquid level of a sample and the arrival at the liquid surface with a simple structure where the electrostatic capacity changes rapidly when arriving at the liquid surface, and the reference value cannot be followed, so that there is no period when the difference between the AC output signal of the electrostatic capacity detecting circuit and the reference value held in the reference value holding circuit becomes smaller than a prescribed threshold in one cycle of the AC output signal. SOLUTION: This liquid level detector is equipped with a reference value holding circuit 5, which holds the peak value of AC output signal of an electrostatic capacity detecting circuit 4 as a reference value, a definite time constant longer than one cycle of the AC output signal, and a liquid level detecting circuit 6, which outputs liquid level detection signals on condition that there is no period when the difference between the AC output signal of the electrostatic capacity detecting circuit 4 and the reference value held in the reference value holding circuit 5 becomes smaller than a prescribed threshold in one cycle of the AC output signal, and does not output it if there is a period when the output signal of a differential circuit becomes smaller than the prescribed threshold in one cycle.
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