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Wiegand Effect
The Wiegand effect is a nonlinear magnetic effect, named after its discoverer John R. Wiegand, produced in specially annealed and hardened wire called Wiegand wire. Wiegand wire is low-carbon Vicalloy, a ferromagnetic alloy of cobalt, iron, and vanadium. Initially, the wire is fully annealed. In this state the alloy is "soft" in the magnetic sense; that is, it is attracted to magnets and so magnetic field lines will divert preferentially into the metal, but the metal retains only a very small residual field when the external field is removed. During manufacture, to give the wire its unique magnetic properties, it is subjected to a series of twisting and untwisting operations to cold-work the outside shell of the wire while retaining a soft core within the wire, and then the wire is aged. The result is that the magnetic coercivity of the outside shell is much larger than that of the inner core. This high coercivity outer shell will retain an external magnetic field even when t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
John R
John R. (born John Richbourg, August 20, 1910 - February 15, 1986) was an American radio disc jockey who attained fame in the 1950s and 1960s for playing rhythm and blues music on Nashville radio station WLAC. He was also a notable record producer and artist manager. Richbourg was arguably the most popular and charismatic of the four announcers at WLAC who showcased popular African-American music in nightly programs from the late 1940s to the early 1970s. (The other three were Gene Nobles, Herman Grizzard, and Bill "Hoss" Allen.) Later rock music disc jockeys, such as Alan Freed and Wolfman Jack, mimicked Richbourg's practice of using speech that simulated African-American street language of the mid-twentieth century. Richbourg's highly stylized approach to on-air presentation of both music and advertising earned him popularity, but it also created identity confusion. Because Richbourg and fellow disc jockey Allen used African-American speech patterns, many listeners thought that ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Magnetic Hysteresis
Magnetic hysteresis occurs when an external magnetic field is applied to a ferromagnet such as iron and the atomic dipoles align themselves with it. Even when the field is removed, part of the alignment will be retained: the material has become ''magnetized''. Once magnetized, the magnet will stay magnetized indefinitely. To demagnetize it requires heat or a magnetic field in the opposite direction. This is the effect that provides the element of memory in a hard disk drive. The relationship between field strength and magnetization is not linear in such materials. If a magnet is demagnetized () and the relationship between and is plotted for increasing levels of field strength, follows the ''initial magnetization curve''. This curve increases rapidly at first and then approaches an asymptote called magnetic saturation. If the magnetic field is now reduced monotonically, follows a different curve. At zero field strength, the magnetization is offset from the origin by an am ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Rotary Encoder
A rotary encoder, also called a shaft encoder, is an electro-mechanical device that converts the angular position or motion of a shaft or axle to analog or digital output signals. There are two main types of rotary encoder: absolute and incremental. The output of an absolute encoder indicates the current shaft position, making it an angle transducer. The output of an incremental encoder provides information about the ''motion'' of the shaft, which typically is processed elsewhere into information such as position, speed and distance. Rotary encoders are used in a wide range of applications that require monitoring or control, or both, of mechanical systems, including industrial controls, robotics, photographic lenses, computer input devices such as optomechanical mice and trackballs, controlled stress rheometers, and rotating radar platforms. Technologies * Mechanical: Also known as conductive encoders. A series of circumferential copper tracks etched onto a PCB is used to ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Magnetic Stripe Card
The term digital card can refer to a physical item, such as a memory card on a camera, or, increasingly since 2017, to the digital content hosted as a virtual card or cloud card, as a digital virtual representation of a physical card. They share a common purpose: Identity Management, Credit card, or Debit card. A non-physical digital card, unlike a Magnetic stripe card can can emulate (imitate) any kind of card. Other common uses include loyalty card and health insurance card; physical driver's license and Social Security card are still mandated by some government agencies. A smartphone or smartwatch can store content from the card issuer; discount offers and news updates can be transmitted wirelessly, via Internet These virtual cards are used in very high volumes by the mass transit sector, replacing paper based tickets and earlier MagStrip cards. History Magnetic recording on steel tape and wire was invented by Valdemar Poulsen in Denmark around 1900 for recording au ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Clock Signal
In electronics and especially synchronous digital circuits, a clock signal (historically also known as ''logic beat'') oscillates between a high and a low state and is used like a metronome to coordinate actions of digital circuits. A clock signal is produced by a clock generator. Although more complex arrangements are used, the most common clock signal is in the form of a square wave with a 50% duty cycle, usually with a fixed, constant frequency. Circuits using the clock signal for synchronization may become active at either the rising edge, falling edge, or, in the case of double data rate, both in the rising and in the falling edges of the clock cycle. Digital circuits Most integrated circuits (ICs) of sufficient complexity use a clock signal in order to synchronize different parts of the circuit, cycling at a rate slower than the worst-case internal propagation delays. In some cases, more than one clock cycle is required to perform a predictable action. As ICs become mo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Keycard Lock
A keycard lock is a lock operated by a keycard, a flat, rectangular plastic card. The card typically, but not always, has identical dimensions to that of a credit card or American and EU driver's license. The card stores a physical or digital pattern that the door mechanism accepts before disengaging the lock. There are several common types of keycards in use, including the mechanical holecard, barcode, magnetic stripe, Wiegand wire embedded cards, smart card (embedded with a read/write electronic microchip), RFID, and NFC proximity cards. Keycards are frequently used in hotels as an alternative to mechanical keys. The first commercial use of key cards was to raise and lower the gate at automated parking lots where users paid a monthly fee. Overview Keycard systems operate by physically moving detainers in the locking mechanism with the insertion of the card, by shining LEDs through a pattern of holes in the card and detecting the result, by swiping or inserting a magnetic ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Low-power Electronics
Low-power electronics are electronics, such as notebook processors, that have been designed to use less electric power than usual, often at some expense. In the case of notebook processors, this expense is processing power; notebook processors usually consume less power than their desktop counterparts, at the expense of lower processing power. History Watches The earliest attempts to reduce the amount of power required by an electronic device were related to the development of the wristwatch. Electronic watches require electricity as a power source, and some mechanical movements and hybrid electromechanical movements also require electricity. Usually, the electricity is provided by a replaceable battery. The first use of electrical power in watches was as a substitute for the mainspring, to remove the need for winding. The first electrically powered watch, the Hamilton Electric 500, was released in 1957 by the Hamilton Watch Company of Lancaster, Pennsylvania. The first quartz ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Magnetic Field
A magnetic field is a vector field that describes the magnetic influence on moving electric charges, electric currents, and magnetic materials. A moving charge in a magnetic field experiences a force perpendicular to its own velocity and to the magnetic field. A permanent magnet's magnetic field pulls on ferromagnetic materials such as iron, and attracts or repels other magnets. In addition, a nonuniform magnetic field exerts minuscule forces on "nonmagnetic" materials by three other magnetic effects: paramagnetism, diamagnetism, and antiferromagnetism, although these forces are usually so small they can only be detected by laboratory equipment. Magnetic fields surround magnetized materials, and are created by electric currents such as those used in electromagnets, and by electric fields varying in time. Since both strength and direction of a magnetic field may vary with location, it is described mathematically by a function assigning a vector to each point of space, cal ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Magnetic Sensor
A magnetometer is a device that measures magnetic field or magnetic dipole moment. Different types of magnetometers measure the direction, strength, or relative change of a magnetic field at a particular location. A compass is one such device, one that measures the direction of an ambient magnetic field, in this case, the Earth's magnetic field. Other magnetometers measure the magnetic dipole moment of a magnetic material such as a ferromagnet, for example by recording the effect of this magnetic dipole on the induced current in a coil. The first magnetometer capable of measuring the absolute magnetic intensity at a point in space was invented by Carl Friedrich Gauss in 1833 and notable developments in the 19th century included the Hall effect, which is still widely used. Magnetometers are widely used for measuring the Earth's magnetic field, in geophysical surveys, to detect magnetic anomalies of various types, and to determine the dipole moment of magnetic materials. In an airc ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Wiegand Sensor
Wiegand sensors are magnetic sensors that do not need any external voltage or current, and make use of the Wiegand effect to generate a consistent pulse every time magnetic field polarity reverses. Wiegand sensors are made by wrapping a coil around a Vicalloy wire core, which, due to the hysteresis inherent in the Wiegand effect, induces a pulse in the coil each time the magnetic polarity of the Vicalloy wire core reverses. They can be used in a range of magnetic sensing applications and have the additional advantage that the energy of each pulse can be harvested. Energy harvesting The consistency of the pulses produced by Wiegand sensors can also be used to provide energy for ultra-low power electronics to be operated using a single pulse. In addition, successive pulses can be stored to offset energy demand of low-power energy circuits. Alternatively, the pulses can be used to trigger, or ‘wake-up’, intermittently powered electronic circuits. In certain applications, both ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Barkhausen Effect
The Barkhausen effect is a name given to the noise in the magnetic output of a ferromagnet when the magnetizing force applied to it is changed. Discovered by German physicist Heinrich Barkhausen in 1919, it is caused by rapid changes of size of magnetic domains (similarly magnetically oriented atoms in ferromagnetic materials). Barkhausen's work in acoustics and magnetism led to the discovery, which became the main piece of experimental evidence supporting the domain theory of ferromagnetism proposed in 1906 by Pierre-Ernest Weiss. The Barkhausen effect is a series of sudden changes in the size and orientation of ferromagnetic domains, or microscopic clusters of aligned atomic magnets (spin (physics), spins), that occurs during a continuous process of magnetization or demagnetization. The Barkhausen effect offered direct evidence for the existence of ferromagnetic domains, which previously had been postulated theoretically. Heinrich Barkhausen discovered that a slow, smooth inc ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Coercivity
Coercivity, also called the magnetic coercivity, coercive field or coercive force, is a measure of the ability of a ferromagnetic material to withstand an external magnetic field without becoming demagnetized. Coercivity is usually measured in oersted or ampere/meter units and is denoted . An analogous property in electrical engineering and materials science, electric coercivity, is the ability of a ferroelectric material to withstand an external electric field without becoming depolarized. Ferromagnetic materials with high coercivity are called magnetically ''hard'', and are used to make permanent magnets. Materials with low coercivity are said to be magnetically ''soft''. The latter are used in transformer and inductor cores, recording heads, microwave devices, and magnetic shielding. Definitions Coercivity in a ferromagnetic material is the intensity of the applied magnetic field (''H'' field) required to demagnetize that material, after the magnetization of the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
