A dynamic measurement of how well an A/D performs. In an ideal A/D converter, a pure sine wave on the analog input appears at the digital output as a pure (sampled) sine wave. In the real world, however, spurious signals due to nonlinear distortion witin the A/D appear in the digital output. These anomalies are usually combinations of harmonics of the fundamental and intermodulation products, produced when the fundamental and its harmonics beat with the sampled frequency.