A contact sensor for the repeatable detection of small, high frequency mechanical vibrations in external systems is presented herein. The sensor includes a metal housing with an attachment device at one end and an output at the other end. Inside the metal housing is a core assembly that includes a piezo transducer assembly suspended or isolated between an actuator and a biasing device. The actuator may be in the form of a ceramic sphere that sits at least partially within a recess on the inside of the housing and is in physical contact with the piezo transducer assembly. The biasing device may be in the form of a spring that causes the piezo transducer assembly to be pressed against the actuator at a contestant and known amount of tension.