The effect of winding and core support material on the thermal gain dependence of a fluxgate magnetometer sensor

Abstract

Abstract. Fluxgate magnetometers are an important tool in geophysics and space physics but are typically sensitive to variations in sensor temperature. Changes in instrumental gain with temperature, thermal gain dependence, are thought to be predominantly due to changes in the geometry of the wire coils that sense the magnetic field and/or provide magnetic feedback. Scientific fluxgate magnetometers typically employ some form of temperature compensation and support and constrain wire sense coils with bobbins constructed from materials such as MACOR machinable ceramic (Corning Inc.) which are selected for their ultra-low thermal deformation rather than for robustness, cost, or ease of manufacturing. We present laboratory results comparing the performance of six geometrically and electrically matched fluxgate sensors in which the material used to support the windings and for the base of the sensor is varied. We use a novel, lowcost thermal calibration procedure based on a controlled sinusoidal magnetic source and quantitative spectral analysis to measure the thermal gain dependence of fluxgate magnetometer sensors at the ppm • C −1 level in a typical magnetically noisy university laboratory environment. We compare the thermal gain dependence of sensors built from MA-COR, polyetheretherketone (PEEK) engineering plastic (virgin, 30 % glass filled and 30 % carbon filled), and acetal to examine the trade between the thermal properties of the material, the impact on the thermal gain dependence of the fluxgate, and the cost and ease of manufacture. We find that thermal gain dependence of the sensor varies as one half of the material properties of the bobbin supporting the wire sense coils rather than being directly related as has been historically thought. An experimental sensor constructed from 30 % glass-filled PEEK (21.6 ppm • C −1 ) had a thermal gain dependence within 5 ppm • C −1 of a traditional sensor constructed from MACOR ceramic (8.1 ppm • C −1 ). If a modest increase in thermal dependence can be tolerated or compensated, then 30 % glass-filled PEEK is a good candidate for future fluxgate sensors as it is more economical, easier to machine, lighter, and more robust than MACOR.

The Origin of Observed Magnetic Variability for a Sol on Mars From InSight

“…The ambient temperature at the sensor head is measured directly. In addition to the winding geometry changes, there can be changes in the magnetic permeability of the sensor mu‐metal core with large temperature variations (Miles et al., 2017).…”

In situ calibration of offsetting magnetometer feedback transients on the Cassiope spacecraft

“…The MGF data processing software (mgftools) described herein is maintained in the Cassiope mission Subversion repository. Release versions of this code are available at: https:// epop.phys.ucalgary.ca/data/ (Miles et al, 2019).…”

MagneToRE: Mapping the 3-D Magnetic Structure of the Solar Wind Using a Large Constellation of Nanosatellites

“…The next-generation, nanosatellite-scale "Tesseract" magnetometer sensor (Figure 7A) leverages low-noise custom fluxgate cores (Miles et al, 2019) to create a compact, rigid, symmetric, and magnetically stable probe. This sensor design also incorporates temperature compensation (Miles et al, 2017), which may be advantageous for some potential trajectories (e.g., lunar orbit; Section 4.2). Each magnetometer would deploy 60 cm from its probe via the BLAZE magnetometer boom (Figure 7B), which is composed of non-magnetic materials (titanium and carbon-fiber with phosphor bronze springs).…”