| 摘要 |
PROBLEM TO BE SOLVED: To provide electrodes and circuits for a liquid level detector capable of detecting an accurate liquid level by simple structure, without being affected by a liquid temperature change, a conductivity change and an electrostatic capacity change. SOLUTION: This system is constituted of the electrode constituted of three electrodes as total comprising one common electrode and two measuring electrodes, and constituted to bring a current ratio by conductive resistances or electrostatic capacities between the common electrode and the respective measuring electrodes into a liquid level according to the liquid level, the transmission circuit 51 for generating an alternating current signal, the transmission output variable circuit 52 for bringing a current value flowing to the electrode 2 or 12 within a prescribed range, the current-voltage conversion circuits 53, 54 for converting the currents flowing in the measuring electrodes into voltages, an AD converter 55 for converting the currents into digital values, and the control circuit 56 and the output circuit 57 provided with functions for acquiring a peak value of the alternating current signal supplied to the electrode 1 or 11 to control the AD converter, for computing the current ratio based on the output values of the AD converter, and for outputting a result as an output signal. COPYRIGHT: (C)2005,JPO&NCIPI
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