Magnet Applications: Hall Effect Sensor

What is a hall effect sensor? Put simply, a hall effect sensor is a transducer that varies its output voltage in response to a magnetic field. As mentioned in previous blogs, a magnetic field has two important characteristics, flux density and polarity. The output signal given from a hall effect sensor is the function of magnetic field density around the device. When the magnetic flux density around the sensor surpasses a certain stipulated threshold, the sensor detects it and generates an output voltage. Consider the below diagram: How do hall effect sensors work? Basically, hall effect sensors are made up of a thin piece of rectangular p-type semiconductor material, which passes a non-stop current through itself. Magnetic flux lines apply a force on the semiconductor material once the device is positioned within a magnetic field. This then deflects the charge carriers, electrons and holes to either side of the semiconductor material. This movement is a result of the magnetic force passing through the material. As these electrons and holes move side wards, the collection of charge carriers cause a potential difference to be produced between the two sides of the semiconductor material. Additionally, the movement of electrons through the semiconductor material is affected by the presence of an external magnetic field. These are positioned at right angles to it, however, it has been proven that this effect is greater when a flat rectangular shaped material is used. Analogue or digital? Hall effect sensors are available with either analogue or digital outputs. For analogue sensors, the output signal is taken directly from the output of the operational amplifier. Here the output voltage is directly proportional to the magnetic field which passes through the hall sensor. The continuous voltage output given by analogue sensors increases with a strong magnetic field and decreases with a weak magnetic field. Notably, as the strength of the magnetic field increases the output signal from the amplifier will also increase. This however, is only until it begins to saturate by the limits forced on it by the power supply. Any additional increase in the magnetic field will have no effect on the output but drive it more into saturation. On the other hand, digital output sensors have a Schmitt-trigger with built in hysteresis connected to the op-amp. Digital output sensors have just two states, “ON” and “OFF”. When the magnetic flux passes through, the hall sensor exceeds a predetermined value. Then, the output from the device switches rapidly from its “OFF” position to an “ON” position without any type of contact bounce. This built-in hysteresis removes any alternation of the output signal as the sensor moves in and out of the magnetic field. Applications Applications include: Automotive systems for the sensing of position, distance and speed. Magnetometers Laboratory instruments Brush-less DC motors Hall effect joysticks used in applications such as diggers, scissor lifts and cranes Hall effect thruster (HET) Wireless Communication Goudsmit UK Goudsmit UK sub-contract manufacture a vast variety of magnets and magnetic assemblies to suit your requirements, no matter the industry. Qualified to ISO 9001, AS9100 and TS16949, we’re the perfect partner for you. Contact us today for more information at info@goudsmit.co.uk or speak to a member of our team call us on +44 (0) 2890 271 001. For more information on our magnetic products visit our webpage or our brochure. Follow us on LinkedIn, Twitter and Facebook for regular updates.

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