Patent ID: 7511477

Claim:
A displacement detector comprising: a constant-current supply unit configured to output a constant current including an alternating current; a coil portion, to which the constant current is supplied; a magnetic core supported to be movable relative to said coil portion in a movable range; and a signal processing circuit configured to determine a displacement of said core to said coil portion in accordance with a change in output voltage of said coil portion under a condition of supplying the constant current to said coil portion; wherein said signal processing circuit comprises: (a) a peak-hold circuit which defines a characteristic-value extracting unit configured to extract a characteristic value from the output voltage of said coil portion, (b) a level shift circuit configured to add a level shift voltage to the characteristic value, (c) an A/D conversion circuit disposed between said peak-hold circuit and said level shift circuit and configured to convert the characteristic value into a digital signal, and (d) a temperature compensation circuit configured to perform a temperature compensation to an output of said level shift circuit; wherein a fluctuation width of temperature coefficient of a total of the characteristic value and the level shift voltage in said movable range is smaller than the fluctuation width of temperature coefficient of the characteristic value in said movable range.