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, lager values of Hall voltage can be generated. The semiconductor material indium arsenide (In As) is generally used. As illustrated in Fig.13-14, 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 to the direction of current. With current in the direction of the length of conductor, the generated voltage is developed across the which.
The amount of Hall voltage v/H is directly proportional to the value of flux density B. This means that gauss meter in Fig.13-15 uses an InAs probe in the magnetic field to generate a proportional Hall voltage v/H. This value of v/H 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.
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