Basics Hall/Reed/Magnet
Basic Knowledge of Hall/Reed/Magnet - Sensors
Hall elements are using the hall effect (an electrical voltage occurs in a current passed conductor that is inside a magnet field) for signal generation. As semiconductor elements, hall elements are mostly integrated in circuits which have additional functions like temperature compensation or amplification.
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Reed contacts consist only of an iron-nickel layer or an iron-gold alloy and are sealed away under protective atmosphere in a glass tube. The contact area consists of a very hard alloy, usually rhodium or wolfram. Reed contacts are switching up to 10kV and 5A with a speed of up to 7 GHz. The sensitivity of a reed switch is given in mT (Millitesla) or Gauss.
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As special form of the hall sensors, MR-sensors additionally have an internal permanent-magnet inside of the sensor housing. The magnetic field that is generated in this way is biased magnetically the hall element and leaving the active area of the sensor. Ferromagnetic materials that enter the magnetic field are taking energy of it and changing the direction of the field lines. Because of the directed change of the field lines, a MR-sensor can detect and evaluate the speed of the target as well as the movement direction. This field change is registered by the hall sensor and the internal sequence control circuit is processing the signal digitally or analogously.
MR-sensors of Pulsotronic detect targets with up to 20 kHz in a temperature range between -40°C and +120°C, independently of the target shape. The module of the gear wheel is used as standard for the optimal function of the MR-sensors..
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