John R. Wiegand

Last updated July 18, 2020

John Richard Wiegand (born 1912, Germany)^[1] 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.

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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.

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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.

References

↑ Brushing Up on Wiegand - he emigrated to the United States in the 1930s to study music (piano and choral conducting) in New York City.

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[1] Brushing Up on Wiegand - he emigrated to the United States in the 1930s to study music (piano and choral conducting) in New York City.