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Glossary - H |
Hall probe
Hall sensor
Hard magnet
Helmholtz coils
Hysteresis loop
Hysteresis loss
Hysteresisgraph
Hall probe
Probe to measure magnetic fields, containing an Hall sensor (see). Hall probes are made in two configurations: transversal and axial. Transversal probes measure magnetic field perpendicularly to the probe (like field produced by yokes or in air gaps). Axial probes measure field in the direction of the axis of the probe (like field from solenoids and long coils).
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Hall sensor
It is a four-terminal solid-state device capable of producing an output voltage proportional to the product of the input current and the magnetic field B perpendicular to the plane of the Hall sensor.
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Hard magnet
Ferromagnetic material with high coercivity (more than 1000 A/m). A hard magnet can store its magnetic energy in a permanent way, because its demagnetizing field is not enough to fully demagnetise it. The reverse is that it is more difficult to magnetize it.
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Helmholtz coils
The Helmholtz coils consist of a set of two identical coils fixed in the same axis at a distance equal to the radius of the coils. This configuration gives a wide homogeneous volume inside. It permits to measure the magnetic polarization JW of the working point (see) of a permanent magnet. It is also possible to create a uniform magnetic field supplying a current to the coil.
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Hysteresis loop
It is a closed curve obtained for a material by plotting the values of magnetic induction B, for the ordinates and magnetising force (or field) H, for abscissa, when the material passes through a complete cycle.
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Hysteresis loss
The energy per unit of mass expended to perform a complete hysteresis cycle. Graphically, it is the area of the cycle (in J/m3).
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Hysteresisgraph
Instrument to measure hysteresis loop and magnetic characteristics of hard magnetic materials. It consists of an electromagnetic yoke, power supply, fluxmeters and measuring coils.
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