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]
Energy harvesting
[edit]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
[edit]Typical applications fall into three main categories; pulse generation applications, power transmission applications and combined sensing and energy harvesting applications.[2]
Pulse generation
[edit]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
[edit]By placing the Wiegand sensor within an oscillating electro-magnetic fields (e.g. from a Helmholtz 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
[edit]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
[edit]- ^ "Google Scholar". scholar.google.com. Retrieved 2020-05-12.
- ^ a b "Wiegand Sensors" (PDF). POSITAL.
- ^ Saggini, Stefano; Ongaro, Fabio; Corradini, Luca; Affanni, Antonio (2015). "Low-Power Energy Harvesting Solutions for Wiegand Transducers". IEEE Journal of Emerging and Selected Topics in Power Electronics. 3 (3): 766–779. doi:10.1109/JESTPE.2015.2424598. S2CID 42681896.
- ^ "Google Scholar". scholar.google.com. doi:10.1109/tmag.2017.2713837. hdl:10131/00012485. S2CID 44644693. Retrieved 2020-05-12.
- ^ "Circuit Parameters of a Receiver Coil Using a Wiegand Sensor for Wireless Power Transmission".
- ^ "WHITE PAPER: Energy Harvesting with the Wiegand Effect" (PDF). POSITAL.