Patent ID: 7129715

Claim:
An oil deterioration detection apparatus comprising a sensing capacitor formed of paired electrodes dipped into oil whose deterioration is to be detected, the oil deterioration detection apparatus detecting deterioration of the oil on the basis of a change in electrostatic capacitance of the sensing capacitor, the apparatus comprising: a measurement signal generation circuit for generating a measurement signal to be supplied to the sensing capacitor in order to measure the electrostatic capacitance of the sensing capacitor; a detection signal output circuit for outputting a detection signal on the basis of a response wave signal produced from the sensing capacitor in response to supply of the measurement signal thereto, the detection signal reflecting the electrostatic capacitance of the sensing capacitor; and an output compensation mechanism for compensating the detection signal for an output level change stemming from a temperature characteristic and/or a time-course deterioration of the detection signal output circuit; wherein the output compensation mechanism comprises a reference element whose impedance temperature coefficient is smaller than that of the sensing capacitor; and an output compensation processing circuit for performing output compensation for the detection signal on the basis of a measured impedance of the reference element; wherein the reference element is a reference capacitor; and the output compensation processing circuit measures electrostatic capacitance of the reference capacitor through measurement of impedance of the reference capacitor; and wherein the reference capacitor has an electrostatic capacitance temperature coefficient of +1% or less within a temperature range of −30° C. to 120° C., wherein an electrostatic capacitance at 20° C. is used as a reference.