1 pT-noise fluxgate magnetometer design and its performance in geomagnetic measurements

We present a design of a low-noise, fundamentalmode, orthogonal fluxgate magnetometer with amorphous wires. The noise obtained in open-loop was as low as 5, 2 and 0.8 pT/√ Hz at 0.1, 1 and 5 Hz, respectively. As the instrument is a self-contained device, powered with batteries, we were able to run a series of geomagnetic measurements and compare them to a low-noise observatory magnetometer. The geomagnetic measurements were performed at the SANSA Space Science facility in Hermanus, South Africa. The offset drift is still an issue, however we show that the instrument is fully suitable for measurements down to 10 mHz. With numeric compensation of the offset drift, sub-mHz measurements are possible. As the instrument is non-cryogenic and portable, more applications, such as magnetotellurics or an unshielded magnetocardiography with a gradiometric sensor, are foreseen.