Hybrid piezoelectric and magnetostrictive actuator

摘要

An acoustic telemetry transducer (12) is formed by an electrical and mechanical combination of a piezoelectric device (18) and a magnetostrictive device (20). The two devices are electrically coupled so that their capacitive and inductive reactances approach a balance to provide an essentially resistive combined input at a selected frequency. Efficiency of circuits driving the transducer is improved. The devices are mechanically coupled so that the mechanical outputs add or reinforce each other. Two transducer pairs may be used in a two frequency telemetry system with each pair tuned to one of the frequencies for optimal reactance balancing and transduction efficiency. The acoustic telemetry transducer is useful for borehole logging. <IMAGE>