Synthesizing signal generator for use with lock-in amplifiers in audiofrequency measurements

摘要

Lock-in amplifiers may be used to measure audiofrequency signals with linearity errors of 10?3 or less. Accuracy is often limited, however, by errors of 1–2 percent in the quadrature separation of the lock-in's polarizing signals. A signal generator is described which in the range 31 Hz–8 kHz provides sinusoidal measuring signals together with a square-wave signal which may be phase-shifted in precise steps of 90°. With this square wave as the external reference of a lock-in, signals may be resolved into orthogonal components with accuracies of 1 in 104. The generator is programmable, and so permits sequences of measurements to be executed under computer control.