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.
The electronics industry relies heavily on devices that acquire, store and transmit data. NVE Corp’s spintronics technology focuses on magnetic sensors, couplers, and memory which perform these activities w...
Furthermore, AMR should be recognized as the combined solid -fluid system, whereby, in essence, a temperature gradient is established throughout the AMR and a fluid is used to transfer heat from the cold end to the hot. This subtle but important idea produced a new magnetic cycle distinct from Carnot, Ericsson, Brayton, or Stirling [6].
...th a growing proportion of elderly people. Global market dynamics and innovations in big data and social networking are transforming the business strategies of companies everywhere—and forcing them to rethink fundamental rules of engagement. For better or worse, the future entrepreneurs will have to surface as one the most disruptive forces. As big data pushes for alternative ways of working – proactive solutions that drive information must quickly figure out which new policies and tools can be utilized most effectively. This grants enormous opportunities for key technological breakthroughs that will be needed for the next generation of transport.
The events leading up to the Rwandan genocide began decades earlier. There has been a long history of “ethnic” tensions, though it is really a matter of social class. The classification began with the German and Belgian colonizers in the early 1900’s. These colonizers created the social classes of “Hutu” and “Tutsi”, and distributed identification cards with such information (Johnson). The genocide was set off when the president’s plane was shot down (Genocide in Rwanda). Though it was never determined who shot the plane down, the Rwandan Patriotic Front, who were Tutsi rebels, have been blamed (The Rwandan Genocide). Immediately following the assassination, violence erupted in the capital city, Kigali. (Genocide in Rwanda)
advance education because of their parents and relatives. As well as Alexie did I learned to read by reading anything I saw and from help by my teacher. I shared what I have learned with my parents so that they will learn with me. It helped me when I was able to read English because the material in school was easier. I wouldn’t be able to have the education I have now because in the United states we might be surrounded by different language but English will always be the main language.
Gestational surrogacy, especially when it involves commercial surrogates, challenges the status quo in the ethical theory of reproduction, because with this technology the process of producing a child can no longer remain a private matter. Now a public contract exists between two parties, the couple and the surrogate ...
A brushless DC motor has a permanent magnet or magnets for the armature. The external magnetic field comes from any number of electromagnets that are turned on and off at the correct times by a timing device.
There is a layer of magnetic material on the surface of the platter. Today, thin-film media is used here. Thin-film media is a microscopic. layer of pure metal bonded to the substrate surface through an interim. layer.
The magnetic susceptibility χ (=M/H) (FC and ZFC) as a function of temperature measured at low applied field (H=50 Oe) is presented in Fig.5. The molar susceptibility shows a monotonic increase upon cooling down to ~ 22 K, where a steeper increase is observed. Below this temperature a bifurcation between the ZFC and the FC curves is evident (see inset of Fig.5. On the other and above 22 K the reciprocal magnetic susceptibility (1/χ) as a function of temperature shows a linear trend (Fig. 5 right scale). In detail, above ca. 30 K, in the paramagnetic region, the Curie-Weiss law is strictly followed. By fitting the linear part of the 1/χ curve with 1/χ = (T-p)/C, in the 30-310 K temperature range, a Curie-Weiss temperature, p = -2.3 K, and the Curie constant, C = 1.30 cm3.K.mol-1, (µeff = 3.2 µB) were obtained. The small negative Curie-Weiss temperature indicates the presence weak antiferromagnetic exchangeinteraction between the Ni magnetic centres. Indeed, the χT curve (Fig. 6 left scale) shows a downward curvature, typical of systems with antiferromagnetic correlations and/or non-negligible spin-orbit coupling. The χT=1.31 cm3.K.mol-1 at 310 K undergoes a small and gradual decrease to 1.19 emu.K.mol-1 at 24.5 K. The Curie constant value, either obtained by1/χ linear fit or the χT product for T>>p is in reasonable agreement with the expected spin-only theoretical value for NiII in octahedral environment with S=1 spin state (C = 1 cm3.K.mol-1and µeff = 2.83 µB considering g = 2) for unquenched orbital moment C = 3.91 cm3.K.mol-1and µeff = 5.59 µB).
People noticed long ago that people from different parts of the world often had different skin tone. For example, people who lived in the tropics usually had darker skin than people who lived in colder climate had lighter skin.
The uses of superconductors are innumerable. They are used in the medical field often, so their use if valuable to common citizens such as yourself and me. Their uses medically include MRI (Magnetic Resonance Imaging) so that doctors do not have to invade the human body for exams, as well as speeding the results of the exams to almost instant information.
This voltage is concentrated in the coil of the read head, and can be interpreted as the data stored on the magnetic disk. When the direction of the flow of electric current is reversed, the magnetic field’s polarity is reversed. The head is mounted in a “slipper” (or holder) positioned above the disk at 0.5-2.5 microns from the surface. When the disk is revolving around its axis, an air current creates a velocity gradient between the surface and air. This creates enough lift to oppose the spring, pressing the head towards the disk.
When the generated fields pass through magnetic materials which themselves contribute internal magnetic fields, ambiguities can arise about what part of the field comes from the external currents and what comes from the material itself. It is common to define another magnetic field quantity, usually called the "magnetic field strength" designated by H. It can be defined by the relationship, H = B0/μ0 = B/μ0 – M, and has the value of unambiguously designating the driving magnetic influence from external currents in a material, independent of the material's magnetic response. The relationship for B can be written in the equivalent form, B = μ0(H + M), H and M will have the same units, amperes/meter. To further distinguish B from H, B is sometimes called the magnetic flux density or the magnetic
A magnet has an invisible field that forces other objects to respond to its properties. This powerful force, which is referred to as the magnetic field, has particles called electrons that actively shift and move within the field. These electrons constantly revolve around the poles, thereby creating energy that attracts objects. Because of this, a magnet has the ability to draw objects towards itself. This ability, which is called magnetism, is caused by the force field that magnets create through its protons (positive charge) and electrons (negative charge).