An electromagnetic coil is an electrical conductor such as a wire in the shape of a coil. Electromagnetic coils are used in electrical engineering, in applications where electric currents interact with magnetic fields, in devices such as electric motors, generators, inductors, electromagnets, transformers, sensor coils such as in medical MRI imaging machines. Either an electric current is passed through the wire of the coil to generate a magnetic field, or conversely, an external time-varying magnetic field through the interior of the coil generates an EMF (voltage) in the conductor.
An inductor, also called a coil, choke, or reactor, is a passive two-terminal electrical component that stores energy in a magnetic field when electric current flows through it. An inductor typically consists of an insulated wire wound into a coil.
Magnetic-core memory is a form of random-access computer memory. It predominated for roughly 20 years between 1955 and 1975, and is often just called core memory, or, informally, core.
A Rogowski coil, named after Walter Rogowski, is an electrical device for measuring alternating current (AC) or high-speed current pulses. It sometimes consists of a helical coil of wire with the lead from one end returning through the centre of the coil to the other end so that both terminals are at the same end of the coil. This approach is sometimes referred to as a counter-wound Rogowski.
A Hall effect sensor is any sensor incorporating one or more Hall elements, each of which produces a voltage proportional to one axial component of the magnetic field vector B using the Hall effect.
Twistor memory is a form of computer memory formed by wrapping magnetic tape around a current-carrying wire. Operationally, twistor was very similar to core memory. Twistor could also be used to make ROM memories, including a re-programmable form known as piggyback twistor. Both forms were able to be manufactured using automated processes, which was expected to lead to much lower production costs than core-based systems.
A proximity card or prox card also known as a key card or keycard is a contactless smart card which can be read without inserting it into a reader device, as required by earlier magnetic stripe cards such as credit cards and contact type smart cards. The proximity cards are part of the contactless card technologies. Held near an electronic reader for a moment they enable the identification of an encoded number. The reader usually produces a beep or other sound to indicate the card has been read.
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.
The Wiegand interface is a de facto wiring standard which arose from the popularity of Wiegand effect card readers in the 1980s. It is commonly used to connect a card swipe mechanism to the rest of an access control system. The sensor in such a system is often a "Wiegand wire", based on the Wiegand effect, discovered by John R. Wiegand. A Wiegand-compatible reader is normally connected to a Wiegand-compatible security panel.
A card reader is a data input device that reads data from a card-shaped storage medium and provides the data to a computer. Card readers can acquire data from a card via a number of methods, including: optical scanning of printed text or barcodes or holes on punched cards, electrical signals from connections made or interrupted by a card's punched holes or embedded circuitry, or electronic devices that can read plastic cards embedded with either a magnetic strip, computer chip, RFID chip, or another storage medium.
An inductive sensor is a device that uses the principle of electromagnetic induction to detect or measure objects. An inductor develops a magnetic field when an electric current flows through it; alternatively, a current will flow through a circuit containing an inductor when the magnetic field through it changes. This effect can be used to detect metallic objects that interact with a magnetic field. Non-metallic substances, such as liquids or some kinds of dirt, do not interact with the magnetic field, so an inductive sensor can operate in wet or dirty conditions.
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, that is ID-1 format. The card stores a physical or digital pattern that the door mechanism accepts before disengaging the lock.
An access badge is a credential used to gain entry to an area having automated access control entry points. Entry points may be doors, turnstiles, parking gates or other barriers.
John Richard Wiegand discovered the Wiegand effect, a physical phenomenon in which a special wire, called a "Wiegand wire", produces small magnetic fields. The accompanying Wiegand reader detects the magnetic pulses produced by the two-domain wire embedded within, typically, plastic cards. There is also a Wiegand interface commonly used to transmit the data collected by a Wiegand sensor in a card reader. The Wiegand effect was first thought to be a commercially viable solution to better ignition systems for internal combustion engines. Echlin Corporation, an automotive parts manufacturer owned Sensor Engineering of Hamden, Connecticut in the 1970s. That application was displaced by the electronic ignition system.
A variety of types of electrical transformer are made for different purposes. Despite their design differences, the various types employ the same basic principle as discovered in 1831 by Michael Faraday, and share several key functional parts.
An MM code is a "machine-readable modulated" feature that has been added to German debit cards during manufacture as an anti-counterfeiting measure since 1979. It was developed by "Gesellschaft für Automation und Organisation" in Munich for the German ec-Card system and MM verification devices have been added to German ATMs from 1982 onwards. If a payment card contains an MM code as well as a magnetic stripe, any fraudster who counterfeits the card but fails to read and duplicate the MM code onto the copy will be detected when trying to use the counterfeit in a German automated teller machine.
An electromagnetic lock, magnetic lock, or maglock is a locking device that consists of an electromagnet and an armature plate.
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, Debit card or driver license. A non-physical digital card, unlike a Magnetic stripe card can emulate (imitate) any kind of card.
In electrical engineering, current sensing is any one of several techniques used to measure electric current. The measurement of current ranges from picoamps to tens of thousands of amperes. The selection of a current sensing method depends on requirements such as magnitude, accuracy, bandwidth, robustness, cost, isolation or size. The current value may be directly displayed by an instrument, or converted to digital form for use by a monitoring or control system.
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.
