Abstract:

In order to avoid   the crosstalk between the measured signal and the reference signal, and the noise introduced during the transmission of the signal in traditional design, a virtual (DLIA:Digital Lock-In Amplifier) based on LabVIEW platform is designed. An  automatic frequency tracking module is used in this design, and the mismatch between the frequencies of the measured signal and the reference signal is greatly reduced. By optimizing the output signal, an excellent waveform was observed, based on the traditional quadrature phase sensitive detection algorithm. The experimental results show that the  SNR(Signal to Noise Ratio) of the measured signal is less than -20 dB, the minimum detectable amplitude is up to 10 μV, and the relative error of the frequencylocking  by the automatic frequency tracking module and that of the measured signal's amplitude are less than 0.02% and 0.05%, respectively.That there is good measuring stability of the designed virtual DLIA  with automatic frequency tracking module.

Key words: signal detection, digital lock-in amplifier(DLIA), automatic frequency tracking, virtual instrument