An electronic circuit is described that allows the use of an inexpensive Hall probe as a high-performance magnetic-field sensor. The circuit contains a high-precision voltage reference, a proportional control thermostat, a 16 bit serial analog-to-digital converter, and a digital control subsystem integrated into a single programmable logic device. The precision of the probe is of about 4 &mgr;T. ©1997 American Institute of Physics.