Methods and apparatus for high cycle fatigue life test

摘要

A capacitance probe (10) measures and tracks frequency and amplitude changes of a component during a high cycle fatigue portion of a life test. The probe includes an internal oscillator (14), an adjustable receiver circuit (16), a product detector (18), and a pair of gain amplifiers (40, 42). The oscillator generates a single controlled frequency output. The receiver circuit receives the frequency and creates a DC voltage shift that nulls the capacitance bridge. The product detector detects an amplitude modulated product of the oscillator and rejects (92) undesirable frequencies. gain amplifiers detect (100) a DC voltage shift and permit the capacitance effect to be easily nulled.