Development of high resolution programmable oversampling MI sensor system with 32-bit ADC for multi-channel bio-magnetic measurements

In order to further improving noise performance and achieving higher spatial resolution for bio-magnetic sensing, there is a tendency to develop a multi-channel integrated system for micro magnetic sensors. In this study, we have developed a high resolution programmable oversampling MI sensor system, as a unit module for multi-channel integrated bio-sensor system, based on Pk-pk VD-type MI magnetometer. We have achieved a high field detection sensitivity with good linearity, and a noise level lower than 1 pT/Hz1/2, by utilizing the time-differential measurement in each MI element for suppressing the low frequency noise components and increasing the stability of sensor system. Meanwhile, the proposed MI sensor system can be easily enlarged into multi-channel system, and is more suitable for integration and mass production. Furthermore, we have successfully achieved the real time R peak and T wave measurements of magnetocardiography (MCG) via new MI sensor system, with a high real time signal-to-noise ratio (SNR) of about 20 dB. We have at the first time achieved the clear P wave measurements of MCG using MI sensor, in an unshielded environment. The real time MCG measurements via new MI sensor system at room temperature, in an unshielded environment, will contribute to the diagnosis of heart disease.