How is a coreless-based current sensor working if there is no concentrator to channel the magnetic field? Basically, the coreless current sensor, also called a field current sensor, has two Hall plates at some distance of each other in the IC, and sits on top of a PCB copper trace or a busbar. When AC or DC current flows in the main conductor, the device senses the field difference between the two places (H1 and H2). The device output is then proportional to the differential field sensed, which is proportional to the applied current, but not to the stray fields that can then be filtered out. The calibration of the conductor as well as the positioning of the sensor is thus crucial in order to get the differential coupling factor right.