In this paper we present the implementation of a digital lock-in amplifier (LIA) completely based on Labview with a general-purpose data acquisition board (or a high quality sound card) and a high-gain low-noise amplifier. The signal analysis is processed by the software. We describe some characteristics of the LIA including output voltage vs. frequency and output phase vs. noise. The LIA can be used to measure the small signals, even in presence of broadband noise which is several times greater than the signal itself. Since the signal processing takes place on the computer, .
