A Ring-Core Fluxgate for Spinner Magnetometer

Abstract

A ring-core fluxgate magnetometer was developed and tuned so as to have ideal characteristics for use as a sensor to a spinner magnetometer for rock magnetism and paleomagnetism. The most important points in this tuning is to obtain high sensitivity as well as flat responses in both amplitude and phase, and to make such characteristics little affected by temperature fluctuations, which is the largest error source in ordinary environment. The present design satisfies all of these requirements. A high sensitivity of 10mV/nT is achieved. The system transfer function is very close to Butterworth low-pass filter, with a cut-off frequency of 450Hz. Moreover, because a very linear phase response was obtained, sampling of magnetic signals at a constant time delay of about 500 microseconds will reproduce signals of 200Hz or less without any distortion. This is ideal for use in the recently developed, advanced spinner magnetometer, as multiple frequency components and/or variable rotational speeds are utilized in such systems.