| 摘要 |
A magnetic field sensor relies on variations in permeability of magnetic material to detect an external field. An exemplary magnetic field sensor includes a magnetic material and two or more conductors, at least one of which is connected to an electrical energy source. Current flowing through at least one of the conductors establishes a magnetic field in the magnetic material at a magnitude at which there is a generally linear relationship between the magnetic field and the permeability of the material. An external field to be sensed influences the permeability of the material. Sensing variations in the permeability of the magnetic material allows the external magnetic field to be sensed. Preferably, the conductors are mutually coupled and exhibit a mutual inductance between each other so that detectable changes in the current distribution between the conductors caused by an external magnetic field may be detected while the net current flowing in the conductors remains sufficient to maintain a magnetic field of sufficient magnitude in the material. The sensitivity of the sensor may be increased by increasing the number of conductors. Sensors may be formed as thin films. Exemplary magnetic sensors are able to detect relatively weak external magnetic fields, such as those emitted by the human brain and other biological bodies and may be used in a variety of applications involving non-contact sensing and monitoring of brain activities or status of consciousness.
|
