Introduction of Hall Effect:
In 1879, E. H. Hall observed that a small voltage is generated across a conductor carrying current in an external magnetic field. The hall voltage was very small with typical conductors, and little use was made of this effect. However, with the development of semiconductors, larger values of Hall voltage can be generated. The semiconductor materials indium arsenide (InAs) is generally used. The InAs element inserted in the magnetic field can generate 60 mV with B equal to 10 KG and an I of 100 mA. The applied flux must be perpendicular, the generated voltage is developed across the width.
The amount of Hall voltage vH is directly proportional to the value of flux density B. This means that values of B can be measured by means of vH. As an example, the Gauss meter uses an InAs probe in the magnetic field to generate a proportional Hall voltage vH. This value of vH is then read by the meter, which is calibrated in Gauss. The original calibration is made in terms of a reference magnet with a specified flux density.