| 摘要 |
PURPOSE:To prevent the fluctuation of output owing to the change in ambient temperature, mechanical vibration, etc. by inserting a variable-impedance element in between the output of an impedance-type sensor and reference potential and by controlling the element according to the integrated value of detection output. CONSTITUTION:Two-phase modulated-wave signal is prepared MD from the output of a signal generator SG and impressed on a series circuit of impedances Z1 and Z2 of the differential impedance type sensor DS. The impedances Z1 and Z2 change differentially according to displacement and the output thereof is subjected to synchronous detection DT and smoothed, whereby detection outputs D and E are obtained. These outputs D and E are further passed through a demodulator DM and thereby demodulation output F is obtained. Based on the difference between the detection output D and reference voltage Er, a control part CT controls the capacity of a variable-capacity diode D, offsets the change in distributed capacity in the output of the sensor DS and stabilizes the fluctuation of a DC signal G caused by the change in temperature, mechanical vibration, etc. |
