Abstract: In a method and a device according to the present invention, two piezo-elements of a piezo-electric actuator are driven with two voltages having a mutual phase difference. One of said piezo-elements is charged by a capacitive voltage step-up means to a voltage exceeding an available power supply voltage. A capacitor is coupled to the piezo-element, which divides the voltage of the piezo-element and simultaneously transfers part of the energy stored in the piezo-element to said capacitor. A part of the energy transferred to said capacitor is later transferred back to said piezo-element, providing an energy-saving feature. The second piezo-element is driven in a similar way providing the required phase difference. In a further embodiment, the waveforms of the two driving signals are corrected using balancing capacitors.

Abstract: The device according to the present invention comprises at least one magnetic field generating element, at least one magneto-resistor and at least one resistance-to-current converter generating a current signal dependent on the resistance value of said at least one magneto-resistor. According to the preferred embodiment of the invention four magneto-resistors are used. A plurality of signals dependent on the ratios of the resistance values of said magneto-resistors are generated, the signals being in different phases. The mutual equality of a predetermined pair of the signals and/or the linear combinations thereof is realized only at predetermined relative positions. The relative position of the movable object is determined by counting the number of such predetermined relative positions passed during the movement of the movable object.