PLANAR THREE-AXIS MAGNETOMETERS USED IN UNSHIELDED MAGNETOCARDIOGRAPHY

Gradiometer is widely used to suppress environmental noise in unshielded magnetocardiography(MCG).However,the efficiency of hardware gradiometer is reduced by the imbalance caused by the imperfection of hand-wound process and the asymmetry of structure.To further suppress the noise,magnetometers are usually applied to compensate the imbalance of hardware gradiometer.We designed and developed the planar three-axis magnetometers based on the low-Tc superconducting quantum interference devices(SQUIDs).By increasing the coupling coefficient between SQUID and its feedback coils,the dynamic range of each magnetometer fulfilled the technical demand of long-time running without overflow,and the crosstalk between the three magnetometers decreased.With the help of the planar three-axis magnetometers,MCG signal with high signal-to-noise ratio was recorded in our unshielded laboratory environment.