The Giant Magneto Impedance phenomenon is known since 1930 and its main application
was measuring extremely weak magnetic fields.
With its proprietary GMI technology (patent granted), FLUX GmbH Austria is the first encoder manufacturer which implemented this physical principle in position measurement systems.
The Giant Magneto Impedance (GMI) is a completely different physical phenomenon than the magnetoresistance and Hall effect which are usually applied in position measuring systems.
Magnetoresistance and Hall effect phenomenons can be explained by the Lorentz force that changes the flow of charge carriers (direct current) in a conductor, when it is placed in an external magnetic field. Consequently by changing the flow path in a conductor of direct current, the resistance of the path changes. The sensors based on these principles have some disadvantages like: position hysteresis (also known as backlash in a drive system), punctual scanning, low signal to noise ratio and relative low accuracy thus limiting their use mostly to “low end” applications. These disadvantages are specific to all types of magnetoresistance sensors: anisotropic (AMR), giant (GMR), tunnel (TMR).
The Giant Magneto Impedance is based on the skin-effect. An external magnetic field changes the permeability and consequently the skin depth of a ferromagnetic material with GMI properties which is passed by an alternating current.