I didn't know much about Hall-effect sensors until I built a solar M&C system (in 2003) and I wanted to accurately measure currents (into/out of battery, out from solar array, and out of auxiliary charger). I didn't want to use shunt resistors because of losses, dealing with voltage offsets, and calibration uncertainty. I ended up using some metrology-grade Closed Loop Hall Effect Current Sensors (F.W. Bell CLN-200).

Hall-effect sensors by themselves are pretty poor for this application, but these sensors consist of a traditional (AC type) current transformer, but instead of a closed core, there's a Hall-effect sensor placed in a small gap in the core loop. Instead of measuring current from the transformer windings, the windings are fed from an op-amp current source with feedback from the Hall-effect sensor with the result that the magnetic field produced by the transformer windings exactly cancels the magnetic field produced from the current flowing through the source cable. The current in the cable is thus known because it equals the product of the CT current and the turns ratio (in this case 200/1).

The Hall-effect sensor here is only sensing the presence or absence of a magnetic field, and the CT is driven to null the field, so the system calibration is simple. (There's no need for any temperature compensation of the Hall-effect sensor.) Also, IIRC, these sensors have a pretty high operational bandwidth (DC to ~200kHz).