To provide a liquid level detection apparatus capable of accurately detecting a liquid level even when liquid spill or dew condensation of a gas phase is generated and even when liquids having respectively different dielectric constants are separated.
When liquid spill is generated in an interdigital electrode, electrostatic capacity CA of a liquid level sensor is increased as shown by a broken line (a), the influence of the electrostatic capacity is increased in accordance with reduction of a liquid level and the influence is reduced in accordance with increase of the liquid level. Also n-times electrostatic capacity n×CB of a warning sensor is similarly increased as shown by a broken line b, influence of the electrostatic capacity is increased in accordance with reduction of the liquid level and the influence is reduced in accordance with increase of the liquid level. When differential capacity CA-B between the electrostatic capacity CA of the liquid level sensor and the n-times electrostatic capacity n×CB of the warning sensor is found out, the differential capacity CA-B is almost equal between existence of liquid spill (refer to symbol e) and no liquid spill and the influence of liquid spill can be canceled. By setting a warning threshold by the differential capacity CA-B, the influence of liquid spill can be suppressed.
| WO/2004/059259 | LIQUID LEVEL DETECTION GAUGE AND ASSOCIATED METHODS |
KATO SHIMPEI
FUKUHARA TOSHIAKI
| JP2007040753A | 2007-02-15 | |||
| JPH11108735A | 1999-04-23 | |||
| JPH03162627A | 1991-07-12 | |||
| JPS6379016A | 1988-04-09 |
| US6443006B1 | 2002-09-03 |
Toshimitsu Ichikawa