To provide an inexpensive controller by providing a low speed A/D converter controlling a displacement sensor and a low speed processor.

Energizing current is inputted to the displacement sensor 21 from the origination means 13 of the controller 10 and a synchronizing signal corresponding to the period of exciting current is outputted from a synchronizing signal generation means 14 to a modulation means 15. The demodulation means 15 outputs a data acquirement command to a conversion means 11 in accordance with the synchronizing signal. The conversion means 11 acquires an output signal from the displacement sensor 21 at timing when the data acquirement command is inputted, executes A/D conversion and transfers the signal to the demodulation means 15. The demodulation means 15 demodulates converted data and a control signal output means 16 controls an actuator 20 in accordance with demodulated data. The conversion means 11 executes A/D conversion only when it receives data acquirement command which is discretely acquired and therefor the controller can be realized with a low speed converter.