This letter presents principles and applications of a virtual multi-channel lock-in amplifier that is a simple but effective method to recover small ac signal from noise with high presison. The fundamentals of this method are based on calculation of
cross-correlation function. Via this method, we successfully built up a magnetoelectric measurement system which can perform precise and versatile measurements without any analog lock-in amplifier. Using the virtual multi-channel lock-in amplifier, the output of the magnetoelectric measurement system is extensively rich in magnetoelectric coupling behaviors, including coupling strength and phase lag, under various dc bias magnetic field and ac magnetic field.
