A multichannel weak magnetic field measuring system for neuromagnetic diagnosis is provided having a plurality of dc-SQUID magnetometers. Bias current setting circuits are provided for detecting an even harmonic component of the output across the terminals of the corresponding SQUID and automatically adjusting a DC bias current to the SQUID. Accordingly, the level of the component becomes a predetermined value. Circuitry is also included for equalizing the magnetic flux detection sensitivities of these dc-SQUID magnetometers. Abnormal operation detecting circuits are also provided for producing abnormal operation detected outputs when the level of the corresponding even harmonic component is smaller than a certain threshold value.
Weak magnetic field measuring system using dc-SQUID magnetometer with bias current adjustment and/or detecting function of abnormal operation