Question

Why the hall voltage should be measured for both the directions of current

Answer 1

Maximum hall voltage is perpendicular to the magnetic field and the current. Sometimes the angles could be a bit off for example the angle could turn out to be 85 or 84 degrees. this slight change leads to the detection of a lower voltage. thus it is necessary to measure from both sides in order to get said lower voltage.

im not sure if this clear please look into other answers as well.

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