Numerical Lock-In Amplifier and Measurement Technique
Original Publication Date: 1987-Aug-01
Included in the Prior Art Database: 2005-Feb-01
Lock-in amplifiers are one of the most widely used instruments in scientific laboratories. The basic function of a lock-in amplifier is to pick up a sinusoidal signal with a given frequency and phase (with respect to a given reference) buried in noise. The conventional lock- in amplifier is basically an analog instrument (although numerical interface facilities are available to digitize the output of the analog unit). Large numbers of active analog devices included in the analog circuit cause various kinds of drifts. As a result, even a state-of- the-art lock-in amplifier will provide an angle resolution of 0.1 degree, which is not sufficient for some applications which are sensitive to very tiny phase drift.