Low frequency magnetic field monitoring using anisotropic magnetoresistances

A dedicated study about magnetic sensing techniques based on anisotropic magnetoresistive sensors has revealed to be a suitable technology for low-frequency space applications like the eLISA mission. Low noise magnetic measurements at the sub-millihertz frequencies have been carried out using different noise reduction techniques in the signal conditioning circuit, where conventional techniques reversing the sensor bridge excitation do not reduce the potential 1/ f noise of the magnetoresistors, and alternative methods are necessary. In addition, a low-frequency noise analysis of the signal conditioning circuits has been performed in order to identify and minimize the different main contributions from the overall noise. The results for chip-scale magnetoresistances exhibit similar noise along the eLISA bandwidth (0.1mHz − 1Hz) than the bulky fluxgate magnetometers used in its precursor mission LISA Pathfinder.