PURPOSE: To provide a variable capacitor which can eliminate the occurrence of errors caused by the shaking of a mobile electrode and a rotational angle detector which can operate over a wide temperature range.
CONSTITUTION: A variable capacitor is composed of a fixed electrode 10 and mobile electrode 11 which can rotate around its axis. The fixed electrode 10 has fixed electrode faces 101-104 arranged on parts of the side face of a first cylinder and the mobile electrode 11 has mobile electrode faces 111 and 112 arranged on parts of the side face of a second cylinder so that the facing areas of the fixed and mobile electrode faces can change in accordance with the rotational angle of the mobile electrode 11. A rotational angle detector is provided with an oscillation circuit, two systems of level changing means which change the levels of AC signals from the oscillation circuit in accordance with the capacitance variation of the variable capacitor, first and second AC-DC converting means which convert the AC signals from the level changing means into DC signals, and differential amplifier means which amplifies the difference between the DC signals from the converting means.
HAGIWARA HIROYUKI
SAKAMOTO NOBORU
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