1980 Volume 32 Issue 10 Pages 649-659
This is a report on the first ring-core type fluxgate magnetometer manufactured in Japan under a cooperative work among the three teams: Tohoku University team, Tohoku Institute of Technology team, and Tokai University team. The ring core consists of 6-81.3 Mo-permalloy tape of 10μm thick and 3mm width wound m times around a ceramic bobbin of diameter d. In order to find the best core, two identical sets of the following twelve different kinds of core were prepared: 5-79 Mo-permalloy and 6-81.3 Mo-permalloy, each with m=9, 12, and 15 turns, and d=20mm and 30mm. One set was examined by the Sendai team (Tohoku Univ. and Tohoku Inst. Tech.) and the other by the Tokai Univ. team. Each of the cores is wound by a 150-turn driving toroidal coil and packed in a 1, 100-turn pickup coil case. When a common ten-volt drive current is applied, the output voltages V for the 12 cores are in the following relations: V6-81>V5-79, V30>V20, and V9>V12>V15. In the next step we applied drive currents with V0=6, 8, 10, and 12 volts, and measured the input power W and the output gain G for various values of the drive frequency f0, and found that G becomes largest for the smallest W at f0=10kHz. Finally we constructed a fluxgate magnetometer with a 6-81.3 ring core of m=9, d=20mm, and f0=10kHz and recorded geomagnetic variations at the Onagawa Magnetic Observatory of Tohoku University. The records were compared with simultaneous records by a commercial fluxgate magnetometer with two-core type sensors. The conclusion is that our ring-core type magnetometer is so sensitive, small, and light in comparison with the previous satellite-borne two-core type magnetometers that, in future, an improved ring-core type one can be loaded on Japanese spacecraft.
