An oscillator or a sensor comprising a unit including two frequency determining elements each of which comprises at least one interdigital converter for acoustic surface waves and a back-coupling circuit comprising an amplifier, wherein the frequency determining elements are distinguished by a temperature dependence of a synchronous frequency. The frequency determining elements are embodied in the form of acoustic surface wave resonators, and the temperature coefficients of n-th order of the synchronous frequency of the two acoustic surface wave resonators have different sings if they are not equal to zero and the temperature coefficients of (n+1st) order of the synchronous frequency of the two acoustic surface wave resonators have the same sign and the temperature coefficients from the first order to (n-1st) order of the synchronous frequency of the two acoustic surface wave resonators are equal to zero if n is greater than 1, wherein n being equal to or greater than 1, c) the ratio between the converter openings and the ratio between the lengths in the direction perpendicular to the edge teeth of the converter and to strips of the object reflectors having different frequency determining elements which are assembled in one unit are selected in such a way that the oscillator frequency variation is minimum within the range of given temperatures.