| 摘要 |
PURPOSE:To ensure easy compensation of nonlinearity of a sensor part, by controlling an oscillating circuit, which applies the oscillated output to a pair of variable capacitors, whose capacities are differentially changed, as specified. CONSTITUTION:The output of an oscillator OSC is applied to capacitors C1 and C2, whose capacities are differentially changed, through a transistor. ACs i1 and i2 flow through the capacitors C1 and C2, which form a sensor, in correspondence with the moving amount X of a movable electrode 10. An average differential current I1-I2 of the currents i1 and i2 is converted to a voltage V0 by a current to voltage converter I/V having a resistor R0. The voltage V0 is inverted and amplified by an inverter circuit IA provided with resistors R1 and R2. A feedback current If is outputted from a resistor R3 and added to one average current I2. The result is applied to an integrating circuit IC, to which a reference current is applied, and the oscillator OSC is controlled by the feedback current. When the current If is adjusted so that the resistance value satisfies the expression I , the voltage V0 becomes the value satisfying the expression II, and easy compensation of the linearity of the sensor can be ensured. In the expression, alpha is a reference interval between the electrode 10 and fixed electrodes 11 and 12 at the time of x=0. |
