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In this article, we present research, development, calibration, and characterization of a novel concept of a digitally compensated, low-noise magnetometer based on anisotropic magnetoresistance sensors that is suitable for space applications. The main idea of the design was to reduce the number of precise analog components while using the digital signal processing power available in a modern microcontroller. Our most recent effort targeted lowering power consumption, enhancement of radiation hardness, and overall improvement of the parameters. The principle of operation is presented in detail, along with a detailed description of the instrumentation used to characterize the real instrument, including its noise, linearity, and temperature stability in the range of −20 °C to +70°C. The results of total ionizing dose (TID) testing at a gamma-ray irradiation facility are discussed at the complete magnetometer and part levels. This is an extended version of an article presented at I2MTC 2020 that contains the results of a second radiation test done with a slightly modified design. The instrument worked well throughout the entire irradiation session (TID of 1.05 kGy over 72 h), and the stability of main parameters was very good (50 pT/Gy offset and 1 ppm/Gy sensitivity stability). [ABSTRACT FROM AUTHOR]

This paper considers the possibilities of using digital feedback for precise anisotropic magneto-resistance (AMR) magnetometers using commercial off-the-shelf (COTS) components. Requiring only a few analog parts, most of the signal processing is done digitally within an STM32 microcontroller. Because most of the precision is made by the feedback circuit, the analog-to-digital converter (ADC) can be a low-cost type. The compensation source is made with a pulsewidth modulation-driven H-bridge sourced from a voltage reference, so the cost reduction when compared to a “full-analog” design is large. The demodulation of a flipped-AMR signal is done with software after the AD conversion because it improves the offset stability and brings the reduction of the preamp’s and ADC’s LF noise. This paper presents the full characterization of a real instrument, including its noise, linearity, stability, and power consumption. [ABSTRACT FROM AUTHOR]

This paper describes a novel method for calibrating dc-precise magnetometers in the low field range ($\pm 100~\mu \text{T}$), which gives acceptable results even in laboratory conditions with significant magnetic interference. By introducing a closely mounted reference magnetometer and a specific calibration procedure, it is possible to compensate for the external magnetic field disturbances caused, e.g., by the local transportation operated with dc power supplies. The field compensation occurs only shortly after the calibrating coils are energized. In this case, the leakage of the coil’s magnetic flux to the reference sensor due to the cancelation of the time-varying compensating field was negligible. When using 60 cm coils and reference sensor in 2.5 m distance, we were able to calculate magnetometer gains with a standard deviation of 91 ppm. We show that an overall uncertainty of 0.1% can be achieved. [ABSTRACT FROM AUTHOR]

A completely nonmagnetic calibration platform has been developed and constructed at DTU Space (Technical University of Denmark). It is intended for on-site scalar calibration of high-precise fluxgate magnetometers. An enhanced version of the same platform is being built at the Czech Technical University. There are three axes of rotation in this design (compared to two axes in the previous version). The addition of the third axis allows us to calibrate more complex devices. An electronic compass based on a vector fluxgate magnetometer and micro electro mechanical systems (MEMS) accelerometer is one example. The new platform can also be used to evaluate the parameters of the compass in all possible variations in azimuth, pitch, and roll. The system is based on piezoelectric motors, which are placed on a platform made of aluminum, brass, plastic, and glass. Position sensing is accomplished through custom-made optical incremental sensors. The system is controlled by a microcontroller, which executes commands from a computer. The properties of the system as well as calibration and measurement results will be presented. [ABSTRACT FROM AUTHOR]

The Chelyabinsk meteorite fragment that landed in the Chebarkul lake in Russia on February 15, 2013 weighed over half a ton. We provide magnetic field maps that were obtained during underwater measurements above the fragment. The data acquisition process was multiple global position system referenced magnetic surveys 0.5–1 m above the top of the lake sediment layer at 10 m water depth. Gradiometric configuration of the survey using two triaxial fluxgate magnetometers helped to suppress local geological anomalies. The location of the ice crater and the underwater magnetic anomaly provided final meteorite landing coordinates, which were made available during meteorite recovery. [ABSTRACT FROM PUBLISHER]

Vector feedback is a concept which can significantly improve linearity and stability of a magnetic field sensor. The feedback coils effectively cancel the measured magnetic field in the inner volume of the triaxial sensor. Thus, in case of fluxgates, it suppresses one possible source of nonlinearity—cross-field sensitivity error. The triaxial sensor axes orthogonality should be primarily defined by the orientation of the feedback coils, while the sensitivities are defined by feedback coil constants. The influence of the homogeneity of the feedback field and the influence of the sensor inner layout on calibration parameters of a vectorially compensated triaxial fluxgate magnetometer are presented. [ABSTRACT FROM PUBLISHER]