Principles and Applications of Ubiquitous Sensing

Chapter 7Magnetic Sensing

Broadly speaking, magnetic sensors can be classified into three major categories. In the first category we find sensors that can sense magnetic fields weaker than the earth's magnetic field (less than ). They are called low-field sensors. In the second category we find sensors capable of sensing magnetic fields in the range of to 10 . This is the range in which the earth's magnetic fields can be contained. The sensors are called medium-field sensors. In the third category we find sensors that can detect fields above 10 . They are called high-field sensors. A magnetic field is a vector quantity, but some sensors are capable of sensing only the magnitude, some only the direction, and others both the direction and the magnitude of a magnetic field.

Low-field sensors are often large and power-hungry, but they have indispensable places in many areas. In medicine, for example, a magnetoencephalogram is used to measure magnetic fields generated in the brain (Sander et al. 2012; Uchiyama et al. 2012; Yasui 2009). Low-field sensors are also fundamental building blocks ...