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.[1] 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.[2]

A Wiegand Sensor and the parts it is made of, including the wrapped coil and the Vicalloy wire.
A Wiegand Sensor.

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.[3]

In certain applications, both functions of the pulses (magnetic sensing and energy harvesting) are exploited. The pulse energy is used to power ultra-low power circuitry or ICs which, in turn, use the timing of the pulses to perform calculation tasks (e.g. count event data).[4]

Applications

Typical applications fall into three main categories; pulse generation applications, power transmission applications and combined sensing and energy harvesting applications.[2]

Pulse generation

As a reliable source of consistently timed pulses, Wiegand sensors are used in industrial and commercial flow-metering applications (e.g. water and gas), and also to calculate rotation speed in tachometers (e.g. high-speed trains).

Power transmission

By placing the Wiegand sensor within an oscillating electro-magnetic fields (e.g. from a Helmholz coil), Wiegand sensors can be used to provide energy for low power applications in environments where high frequency transmission is challenging (e.g. transcutaneous power for medical devices).[5]

Sensing and energy harvesting

Wiegand sensors are commonly used in ‘Batteryless’ rotary encoder technology for self-powered revolution counting. Harnessing both the timing of the pulses and the pulse energy, such rotary encoders provide reliable multiturn counting even in the absence of external power or batteries.[6]

References
  1. "Google Scholar". scholar.google.com. Retrieved 2020-05-12.
  2. "Wiegand Sensors" (PDF). POSITAL.
  3. "Low-Power Energy Harvesting Solutions for Wiegand Transducers".
  4. "Google Scholar". scholar.google.com. doi:10.1109/tmag.2017.2713837. Retrieved 2020-05-12.
  5. "Circuit Parameters of a Receiver Coil Using a Wiegand Sensor for Wireless Power Transmission".
  6. "WHITE PAPER: Energy Harvesting with the Wiegand Effect" (PDF). POSITAL.
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