| 摘要 |
PURPOSE: To detect the concentration of an additive of an unknown fuel quickly by referring to a map having a known concentration range of the additive formed based on a signal difference by a first and a second signal detection mans with the use of a capacitive sensor. CONSTITUTION: A capacitive sensor 15 detects as a static capacitance the change of a dielectric constant due to a state of gasoline flowing in a piping. First voltages VH, VH are impressed to a first electrode 18 (18A, 18B) and a second electrode 19 (19A, 19B) of the sensor 15, and a first detection voltage VOA from a processing circuit 28 is read into a control unit 36. Then, second voltage VH, VL are impressed to the electrodes, and a second detection voltage VOB is read into the unit 36. The unit 36 operates a voltage differenceΔV=VOA-VOB from the voltage VOA, VOB. Based on the operated voltage differenceΔV and detection voltage VOA, a concentration range of additives in the unkown fuel is decided with reference to a map having a known concentration range in a memory area 36A.
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