Abstract
Abstract. A proof-of-concept hybrid magnetometer is presented, which simultaneously operates as both a fluxgate and a search coil, allowing it to sense the magnetic field from DC to 2 kHz using a single sensor. Historically, such measurements would normally require two dedicated instruments, and each would typically require deployment on its own dedicated boom as the instruments mutually interfere. A racetrack fluxgate core combined with a long solenoidal sense winding is shown to be moderately effective as a search coil magnetometer, and the search coil effect can be captured without introducing significant hardware complexity beyond what is already present in a typical fluxgate instrument. Several methods of optimising the search coil action of the hybrid instrument are compared with the best method providing sensitivity and noise performance between comparably sized traditional air-core and solid-core search coil instruments. This hybrid sensor topology should miniaturise to platforms such as CubeSats for which multiple boom-mounted instruments are generally impractical, so a single hybrid instrument providing modest, but scientifically useful, sensitivity from DC to kHz frequencies would be beneficial.
Highlights
Introduction and motivationSpace science missions (e.g. Angelopoulos, 2009; Kessel et al, 2013) often need two magnetic field instruments – a search coil magnetometer for high ( ≥∼ 10 Hz) frequencies (Fig. 1a) and a fluxgate for the static field and low frequencies (Fig. 1b)
Search coil magnetometers and fluxgate magnetometers (Hospodarsky, 2016; Primdahl, 1979) both sense the local magnetic field through the electromagnetic force (EMF) induced by changing magnetic flux described by the generalised induction equation (Eq 1) for a coil of wire of N turns and area A, in a field H, with a ferromagnetic core of relative permeability, μr: dd dH
This paper describes a proof-of-concept hybrid magnetometer which explores whether both the search coil and fluxgate sense
Summary
Space science missions (e.g. Angelopoulos, 2009; Kessel et al, 2013) often need two magnetic field instruments – a search coil magnetometer for high ( ≥∼ 10 Hz) frequencies (Fig. 1a) and a fluxgate for the static field and low frequencies (Fig. 1b). These two instruments will interfere with each other if they are located too close together. Search coils typically have no single dominant noise source, so compact space instruments tend to use a long ferromagnetic core for magnetic gain and tens of thousands of turns of wire to increase sensitivity. Since fluxgate sensitivity is essentially flat with frequency and search coil gain tends to increase with frequency until the self-resonance
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