Magneto-optical/magnetic data carrier e.g. hard disk, demagnetising device, for use in lorry, has frequency adjusting device to decrease voltage frequency until measured amplitude of current flowing at resonance circuit is adjusted to value

摘要

The device has an excitation winding interconnected with a capacitor (5) of a resonance circuit that is fed over an inverter. An output voltage of the inverter is synchronized to a frequency of the circuit. A current measuring device measures amplitude of current flowing at the circuit. A frequency adjusting device (13) decreases a frequency of an input terminal voltage until the measured amplitude is adjusted to a preset value.