Piezoelectrically driven ultrasonic generator

Ultrasonic system for measuring fluid flow by comparing the responses from pulsed beams transmitted obliquely in opposite directions through fluid flowing in a pipe section. The transducer assembly includes a driving element comprising a piezoelectric generator in the form of a disk with a high mass backing element bonded to one face and an acoustic wave transformer bonded to the other face. The wave transformer element varies in cross-section in an axial direction, comprising disks of maximum dimension at the generator face and at the radiating face, which are separated by a connecting portion of minimum dimension. In preferred form, the wave transformer is shaped like a barbell. An advantage of this configuration is that the beam pattern is a function of frequency, having a dominant central lobe at about 45 kilocycles per second which becomes relatively depressed with respect to increasing side lobes as the frequency is increased. Although the invention has been described in general terms, the primary uses of the system and components as disclosed herein are for the measurement of the flow of gases.