Abstract: In a method and a circuit arrangement for operating an ultrasound oscillation system, wherein an excitation voltage is applied to an ultrasound oscillation system comprising an ultrasound oscillator and components for forming an oscillation circuit for generating an excitation current and wherein the frequency of the excitation voltage is adjustable for operating the ultrasound oscillation system at a predetermined operating point, upon switching on the ultrasound oscillation system, the frequency, beginning with a startup frequency, is changed until the operating point is reached, and, upon switching off the ultrasound oscillation system, the frequency of the excitation circuit is recorded in a storage device and the recorded value is used for determining the startup frequency when the ultrasound oscillation system is again switched on.

Abstract: In a method and a circuit arrangement for operating an ultrasound oscillator with a constant oscillation amplitude wherein an excitation voltage U, whose frequency is disposed outside the resonance frequency of an ultrasound oscillation system, is applied to the ultrasound oscillator which includes components forming therewith an oscillation circuit for generating an excitation current I, whose size is adjusted by changing the frequency of the excitation voltage U to a predetermined value, the level of the excitation voltage U is detected by a voltage sensor and the predetermined value of the size of the excitation current I is set depending on the level of the excitation voltage U.