Abstract: An Eddy Currest Tester for detecting defects in conductive materials employs phase rotation circuitry for eliminating the effects of lift-off signals from the reactive component of the output of an eddy current probe. An operator digitally selects a frequency which is input to the eddy current probe which is adjacent a test material. The signal output from the eddy current probe is amplified and demodulated into reactive and resistive components which are processed by phase rotation circuitry. The phase rotation circuitry is calibrated by applying a lift-off signal thereto while a phase adjust switch is on. When the phase adjust switch is on the reactive signal component is applied to a zero crossing detector which in conjunction with a flip flop controls the counting direction of an counter which addresses a sine-cosine table in a eraseable programable read only memory.