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

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.

Evaluation of the Performance of Micro-Drills in Drilling a Machinable Ceramic Material

The performance of three different micro-drills in drilling a machinable ceramic material has been evaluated in terms of the critical feed speed (mm/min) at a given rotation rate (rpm). The critical speed is the feed speed from and above which the chipping on the rear side of the machinable ceramic material takes place. The determined critical speed turns out to increase with rotation rate in the tested range of 2k-8k rpm, forming the critical boundary line. The drilling performance of the micro-drills can be evaluated quantitatively by using the position of the critical boundary lines in the space of feed speed vs. rotation rate: the upper the critical boundary line, the higher the drilling performance of the micro-drill.

Influence of Parameters on Microstructure of CePO4/ZrO2 Machinable Ceramics

Machinable ceramic was widely attended for it could extend application range of ceramic. As a kind of common ceramic, ZrO2 ceramic was used widely, but it was difficult to be machined. CePO4 powder was added into ZrO2 powder to prepare composite powder. In this paper, two dispersion methods were used to prepared composite powder: mechanical mixed method and flocculation of multiphase suspension were used. Composite powder that prepared by mechanical mixed method sintered at 1450°C, 1550°C and 1600°C respectively. SEM was used to study microstructure of samples. Result of SEM showed that microstructure of sample that sintered at 1550°C was better than others, and there was no obviously default was found in it. Effect of mechanical mixed method was better than flocculation of multiphase suspension in this paper.