Sensitive ac Hall Effect Circuit

A description is given of a Hall effect circuit which uses a constant magnetic field and a 270 cps alternating current source supplying the driving current to the sample. Provision is made for canceling voltages caused by misalignment of the Hall voltage probes as well as other unwanted voltages induced from the driving circuit. The cancelation of the unwanted voltages is accomplished within the sample by controlling the current distribution so that the unwanted voltages never appear at the Hall voltage probes. This allows the detector circuitry to be kept simple, keeps shielding problems to a minimum, and eliminates the necessity for using balancing resistors in the low level Hall voltage circuit. Sensitivity compares favorably with other ac methods.