The magnetoelectric (ME) effect is an electric output in response to an applied magnetic field. In a heterostructure configuration where the two-phases are engineered with close interface contact, a giant electric response to a magnetic field has been found, which is designated as the ME voltage (or charge) coefficient α^ME. This effect is mediated by a mechanical-coupling between magnetostrictive and piezoelectric phases. In this thesis, I concentrate on application study for ME sensors with respect to noise control and rejection, thermal stability, triple-axis sensor design, array imaging, DC and AC magnetic sources detection and active mode ME sensor development, which is important for future ME sensor device applications.