Sound generator for fatigue testing has a control circuit with a phase control circuit, which incorporates a phase detection circuit, that is used to quickly tune the sound applied to the test-piece to its resonance frequency

摘要

Control circuit for a sound generator (SCH) for a test piece (PSK) has an amplitude sensor (SEN), an amplitude control circuit and a phase control circuit that incorporates a phase detection circuit (PHD). A first square-wave measurement signal (e1), which is derived from a first sensor signal (ss), and a second square-wave signal (e2), which is derived from the output signal of an oscillator (VCO), are applied to the phase detection circuit. The latter determines the time difference between two signal flanks and generates a proportional voltage signal. The process interates until the phase difference is zero.