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Geoscientific Instrumentation, Methods and Data Systems An interactive open-access journal of the European Geosciences Union

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Geosci. Instrum. Method. Data Syst., 6, 377-396, 2017
https://doi.org/10.5194/gi-6-377-2017
© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 3.0 License.
Research article
11 Oct 2017
The effect of winding and core support material on the thermal gain dependence of a fluxgate magnetometer sensor
David M. Miles1,2, Ian R. Mann2, Andy Kale2, David K. Milling2, Barry B. Narod3,4, John R. Bennest5, David Barona2, and Martyn J. Unsworth2 1Department of Physics and Astronomy, University of Iowa, Iowa City, IA, USA
2Department of Physics, University of Alberta, Edmonton, AB, Canada
3Narod Geophysics Ltd., Vancouver, BC, Canada
4Department of Earth, Ocean and Atmospheric Sciences, University of British Columbia, Vancouver, BC, Canada
5Bennest Enterprises Ltd., Summerland, BC, Canada
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, low-cost 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 MACOR, 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.

Citation: Miles, D. M., Mann, I. R., Kale, A., Milling, D. K., Narod, B. B., Bennest, J. R., Barona, D., and Unsworth, M. J.: The effect of winding and core support material on the thermal gain dependence of a fluxgate magnetometer sensor, Geosci. Instrum. Method. Data Syst., 6, 377-396, https://doi.org/10.5194/gi-6-377-2017, 2017.
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Short summary
Fluxgate magnetometers are an important geophysical tool but are typically sensitive to changes in sensor temperature. We used a novel, low-cost calibration procedure to compare six matched sensors in which the material used as the mechanical support is varied and found that 30 % glass-filled PEEK engineering plastic is a good candidate for sensors. It is more economical, easier to machine, lighter, and more robust than historically used machinable ceramic.
Fluxgate magnetometers are an important geophysical tool but are typically sensitive to changes...
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