GMR Applications :: science

GMR Applications A Microcontroller-based scheme for measurement of magnetic field position using Giant Magnetic Resistor (GMR) in Contactless Measurement and Robotics Omidreza Esmaeili Motlagh Faculty of Electronic Engineering, Mazandaran University ( UMZ ), Babol, Iran Magnetic sensors in contactless applications: Magnetic sensors can be used for all sorts of applications where a contactless measurement of position and orientation is required. For instance in cars, where a large number of sensors are employed, magnetic sensors obviously have great advantages over their counterparts which involve the use of moving parts. Also they are variety of Magnetic sensors used in industry to simplify designs in different cases. For instance the current measurement using shunt resistor is in some cases impractical or impossible. For large currents the shunt resistors are heavy and they cause voltage drop and dissipate heat. They are not insulated and the conductor should be disconnected for mounting. Contactless current sensors may be used for remote conductors at high potentials, underground cables etc. Today a wide range of AC and DC contactless current sensors is produced. Also precise contactless magnetic sensors are always required by car industry, chemical industry and many other industries, for measurement of power and many other applications. Solid-state magnetic field sensors are moving into a growing range of new contactless applications because of their small size, low power consumption, and relatively low cost. The first aim of the project therefore will be to become familiar with different kinds of magnetic sensors, especially new GMR family and to investigate their characteristics and behavior in presence of applied magnetic field. [1] Giant Magnetic Resistor (GMR): Structure: The sensor consists of stack of magnetic and non-magnetic layers and Giant Magnetic Resistivity or GMR effects occur when these ultra-thin magnetic layers are set in close proximity to each other. Alternately magnetic and non-magnetic layers can be built up with the magnetic fields either parallel or anti-parallel, creating very sensitive low to high resistance components. The resistance of a GMR sensor as a measure for the applied field varies with the angle between the hard internal magnetization and the soft magnetic covering layers which follows the magnetic field. [2] The Giant Magnetic Resistor is a resistive device whose Ohmic value changes gradually only when a nearer external magnetic field changes its relative orientation and the originated field intensity or the distance between magnet and GMR are not relevant within certain limits. Any rotary button or knob containing a magnet on it, may work as a contactless switch when its rotation is detected by a GMR.