High sensitivity 50 Hz-1 MHz probe for B and dB/dt

An accurate broadband sensor for the analysis of magnetic induction B in the range 10 nT-5 mT is presented. Choosing appropriate amplifier circuits allows measurement of either B or dB/dt, in the frequency range 50 Hz-1 MHz, which makes it possible to detect very weak high-frequency fields with attenuation of the 50 Hz power frequency. The probe is also suitable for on-site measurements of common-mode currents in cables with a resolution of about 10 mA. It has high immunity against electric fields and is useful both for time-domain measurements and for frequency-domain measurements.