Wiegand Effect

Information about Wiegand Effect

The Wiegand effect is named after its discoverer, John R. Wiegand.

Overview

The Wiegand effect is a pulse-generating phenomenon in a special alloy wire that is processed in such a way as to create two distinct magnetic regions in the same homogeneous piece of wire, referred to as a shell and a core. It occurs when such a specially processed wire (a "Wiegand wire") is moved past a magnetic field. The two distinct magnetic regions react differently to any applied magnetic field: the shell requires a strong magnetic field to reverse its magnetic polarity, whereas the core will revert under weaker field conditions. The polarity of the wire will very rapidly shift and generate strong, short (~10 µs) electrical pulses without any additional external power being supplied. This is known as the "Barkhausen jump" or "Barkhausen effect". The Barkhausen jump can be detected by a coil wrapped around the material, when the small amount of voltage described above is generated.

Wiegand wire

Wiegand wire is produced by cold-working a 0.010 inch (0.254 millimeter) diameter ferromagnetic wire made of Vicalloy, a mixture of cobalt, iron, and vanadium. The cold-working process consists of increasing amounts of twist and de-twist of the wire under applied tension in several steps. The wire is then age-hardened to hold in the tension built up during the cold-working process. This procedure causes the Wiegand wire to have a soft magnetic center, the core, and a work-hardened surface with a higher magnetic coercivity, the shell. When an alternating magnetic field of proper strength is applied to the Wiegand wire, the core's magnetic field will switch polarity and then reverse again, causing a Wiegand pulse to be generated.

The patented cold-working process that produces the Wiegand wire permanently locks in the ability to exhibit Barkhausen effect discontinuities in the material. To achieve magnetic switching, the wire is put in the presence of alternating longitudinal magnetic fields. The resultant hysteresis loop contains large discontinuous jumps known as Barkhausen discontinuities that occur due to shell and core polarity switching.

Uses in sensor technology

Sensor based on the proprietary and patented Wiegand effect require only a few simple components: a short length of Wiegand wire, a sensing coil, and alternating fields, which are generally derived from small permanent magnets. Sensors of this type can be used across a wide range of conditions. The Wiegand effect occurs from -80 degrees Celsius to 260 degrees Celsius. Wiegand effect sensors are used in water, gas, and electric meters for electronic indexing. They also have many automotive applications such as antilock braking, speed sensing, and position indicators. They have been used in anemometers and other wind speed applications, machine controls, shaft speed sensing, and numerous rotational counting applications. Wiegand wires are also used in access control systems.

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
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Work hardening, or strain hardening, is an increase in the strength of a material due to plastic deformation. In metallic solids permanent change of shape is usually carried out on a microscopic scale by defects called dislocations which are created by stress and rearrange
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In metallurgy, vicalloy is a precipitation-hardening, ductile permanent magnet alloy capable of being processed into strip, bar, and wire products prior to heat treatment for electromechanical device applications (such as Wiegand wires).

It consists of 0.03% carbon, 0.
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2, 3
(amphoteric oxide)
Electronegativity 1.88 (Pauling scale)
Ionization energies
(more) 1st: 760.4 kJmol⁻¹
2nd: 1648 kJmol⁻¹
3rd: 3232 kJmol⁻¹

Atomic radius 135 pm
Atomic radius (calc.
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3, 4, 6
(amphoteric oxide)
Electronegativity 1.83 (Pauling scale)
Ionization energies
(more) 1st: 762.5 kJmol⁻¹
2nd: 1561.9 kJmol⁻¹
3rd: 2957 kJmol⁻¹

Atomic radius 140 pm
Atomic radius (calc.
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5
(amphoteric oxide)
Electronegativity 1.63 (Pauling scale)
Ionization energies
(more) 1st: 650.9 kJmol⁻¹
2nd: 1414 kJmol⁻¹
3rd: 2830 kJmol⁻¹

Atomic radius 135 pm
Atomic radius (calc.
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coercivity, also called the coercive field, of a ferromagnetic material is the intensity of the applied magnetic field required to reduce the magnetization of that material to zero after the magnetization of the sample has been driven to saturation.
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An access badge is the identification used to gain entry to the office or other places that have automated access controlled entry points. Entry points may be doors, turnstiles, parking gates or other controlled entry points.
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piece of identification (ID) is a document designed to verify aspects of a person's identity. It is also called an identity document or, if in the form of a small standard-sized card, an identity card (IC).
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Physical security describes measures that prevent or deter attackers from accessing a facility, resource, or information stored on physical media. It can be as simple as a locked door or as elaborate as multiple layers of armed guardposts.
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Proximity card is a generic name for contactless integrated circuit devices used for security access or payment systems. It can refer to the older 125 kHz devices or the newer 13.56 MHz contactless RFID cards, most commonly known as contactless smartcards.
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Radio-frequency identification (RFID) is an automatic identification method, relying on storing and remotely retrieving data using devices called RFID tags or transponders.
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Security is the condition of being protected against danger or loss. In the general sense, security is a concept similar to safety. The nuance between the two is an added emphasis on being protected from dangers that originate from outside.
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Security engineering is the field of engineering dealing in developing detailed engineering designs for security systems and for security of spaces. It is similar to systems engineering in that its motivation is to make a system meet requirements, but with the added dimension of
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The Wiegand interface is a defacto wiring standard which arose from the popularity of Wiegand effect RFID card readers in the 1980s. It is commonly used to connect a card swipe mechanism to the rest of an electronic entry system.
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