John R. Wiegand discovered the Wiegand effect

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....

, a physical phenomenon in which a specially constructed Wiegand wire can detect small magnetic fields. The Wiegand wire is commonly used as a sensor to read security access cards. There is also a Wiegand Protocol commonly used to transmit the data collected by a Wiegand sensor in a card reader.