| 摘要 |
PROBLEM TO BE SOLVED: To provide a capacitive level detector which does not incorrectly operates, even if a housed substance is attached to the electrode. SOLUTION: The level detector includes the main electrode 2 and a ground electrode 4 attached so as to protrude into a housing container 6; a capacitance-voltage transducer 11 for transducing an alternating voltage from a high-frequency oscillator 11a into the magnitude according to the capacitance between the electrodes 2 and 4; a synchronization rectifying circuit 12 for rectifying the alternating voltage outputted from the capacitance-voltage transducer 11 by detecting, in synchronization with the high-frequency oscillator, only the component having the phase shift of 90 degrees; and a comparator 13 for comparing a direct voltage outputted from the synchroninous rectification circuit 12 with a reference voltage. COPYRIGHT: (C)2005,JPO&NCIPI
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