Christophe Coillot

Induction Magnetometers Principle, Modeling and Ways of Improvement

This book provides an introductory overview of the research done in recent years in the area of magnetic sensors. The topics presented in this book range from fundamental theories and properties of magnets and their sensing applications in areas such as biomedicine, microelectromechanical systems, nano-satellites and pedestrian tracking. Written for the readers who wished to obtain a basic understanding of the research area as well as to explore other potential areas of applications for magnetic sensors, this book presents exciting developments in the field in a highly readable manner.

Very Low 1/f Noise and Radiation-Hardened CMOS Preamplifier for High-Sensitivity Search Coil Magnetometers

A 4 nV/√(Hz) at 10 Hz preamplifier with a 12-mW power consumption in complimentary metal-oxide-semiconductor 0.35 μm technology has been developed to go one step further in the integration of the preamplifier of a search coil magnetometer. The present application-specific integrated circuit (ASIC) preamplifier, combined with a 10-cm length, 12-mm diameter, and 15 000 turns search coil sensor demonstrates a noise equivalent magnetic induction as low as 2 pT/√(Hz) at 10 Hz and 14 fT/√(Hz) at 4 kHz. The measured current noise is only 46 fA/√(Hz). AC magnetometers (from 100 mHz to a few kHz) based on search coil sensors are used for space plasma physics investigations because of their excellent robustness and very high sensitivity. The present ASIC preamplifier offers a way to considerably save weight, volume, and power. This paper will focus on the design of the ASIC, driven by the following criteria: low thermal and 1/f noise, radiation hardness for space purpose, and power consumption.

Autocalibration Method for Anisotropic Magnetoresistive Sensors Using Offset Coils

In this paper, we present a zero-cost indoor calibration method for anisotropic magnetoresistive (AMR) sensors. The implemented circuit is designed to calibrate AMR sensors using integrated coils. A microcontroller is used to generate an artificial three-dimensional magnetic field by injecting three separate currents into three offset coils. We show the similarity of the results for residual calibration norm by using this method compared with the calibration of the sensor in free Earths magnetic field. Furthermore, this method does not need any other instruments such as Helmholtz coils or a platform for rotating the sensor. Here the sensor is placed inside a mu-metal box during calibration, and the calibration process is completely autonomous.