Wiegand sensors are magnetic sensors that do not need any external

voltage Voltage, also known as electric pressure, electric tension, or (electric) potential difference, is the difference in electric potential between two points. In a static electric field, it corresponds to the work needed per unit of charge to m ...

or current, and make use of the

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. Wiegand wire is low-carbon Vicalloy, a ferromagnetic alloy of cobalt, iron, and ...

to generate a consistent pulse every time

magnetic field A magnetic field is a vector field that describes the magnetic influence on moving electric charges, electric currents, and magnetic materials. A moving charge in a magnetic field experiences a force perpendicular to its own velocity and to ...

polarity reverses. Wiegand sensors are made by wrapping a coil around a

Vicalloy Vicalloy is a family of cobalt-iron-vanadium wrought ferromagnetic alloys which have high coercivity and are used to make permanent magnets and other magnetic components. Vicalloy is precipitation hardened and can be formed by a number of cold ...

wire core, which, due to the hysteresis inherent in the

, induces a pulse in the coil each time the

magnetic polarity A magnet is a material or object that produces a magnetic field. This magnetic field is invisible but is responsible for the most notable property of a magnet: a force that pulls on other ferromagnetic materials, such as iron, steel, nicke ...

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.

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. In certain applications, both functions of the pulses (magnetic sensing and

energy harvesting Energy harvesting (EH, also known as power harvesting or energy scavenging or ambient power) is the process by which energy is derived from external sources (e.g., solar power, thermal energy, wind energy, salinity gradients, and kinetic energ ...

) 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).

Applications

Typical applications fall into three main categories; pulse generation applications,

power transmission Power transmission is the movement of energy from its place of generation to a location where it is applied to perform useful work. Power is defined formally as units of energy per unit time. In SI units: :\text = \frac = \frac Since the develo ...

applications and combined sensing and

applications.

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 Rotational frequency (also known as rotational speed or rate of rotation) of an object rotating around an axis is the frequency of rotation of the object. Its unit is revolution per minute (rpm), cycle per second (cps), etc. The symbol for ...

in tachometers (e.g.

high-speed trains High-speed rail (HSR) is a type of rail system that runs significantly faster than traditional rail, using an integrated system of specialised rolling stock and dedicated tracks. While there is no single standard that applies worldwide, lines ...

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 A medical device is any device intended to be used for medical purposes. Significant potential for hazards are inherent when using a device for medical purposes and thus medical devices must be proved safe and effective with reasonable assura ...

Sensing and energy harvesting

Wiegand sensors are commonly used in ‘Batteryless’

rotary encoder A rotary encoder, also called a shaft encoder, is an electro-mechanical device that converts the angular position or motion of a shaft or axle to analog or digital output signals. There are two main types of rotary encoder: absolute and increme ...

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 Power most often refers to: * Power (physics), meaning "rate of doing work" ** Engine power, the power put out by an engine ** Electric power * Power (social and political), the ability to influence people or events ** Abusive power Power may a ...

or batteries.

References

{{reflist Magnetic devices