A method to measure an electric current, comprising: providing a pair of conductive wires having corresponding first and second ends, said pair of wires being disposed so as to be equidistant over their full extents, said corresponding first ends being electrically connected to each other; placing, on each of said wires, a magnetic sensor having top and bottom leads between which a voltage drop occurs in the presence of a magnetic field, each such sensor having a free layer and a reference layer (3, 4, 5) having pinned magnetization, characterized in that said free layer and said reference layer have the form of a plurality of independent sensor stacks, each such stack having, in plan view, an aspect ratio of at least 1.2 and a length dimension of at most 1 micron and perpendicular to a direction of said pinned magnetization whereby all free layers of said sensor stacks are domain stable in the presence of a magnetic field and wherein said top and bottom leads are common to all said sensor stacks; and it that said method further comprises: providing a source of constant current for driving said magnetic sensors; passing said current between said corresponding second ends, thereby generating a magnetic field whose direction is different relative to each of the sensors whereby said sensors generate voltage drops whose magnitudes differ from one another, wherein a voltage drop generated by a sensor is an average of indivudual voltages generated by each said sensor stack; using a differential voltage amplifier to measure said difference in magnitude between said voltage drops; and thereby deriving a value for said electric current. providing a pair of conductive wires having corresponding first and second ends, said pair of wires being disposed so as to be equidistant over their full extents, said corresponding first ends being electrically connected to each other; placing, on each of said wires, a magnetic sensor having top and bottom leads between which a voltage drop occurs in the presence of a magnetic field, each such sensor having a free layer and a reference layer (3, 4, 5) having pinned magnetization, characterized in that said free layer and said reference layer have the form of a plurality of independent sensor stacks, each such stack having, in plan view, an aspect ratio of at least 1.2 and a length dimension of at most 1 micron and perpendicular to a direction of said pinned magnetization whereby all free layers of said sensor stacks are domain stable in the presence of a magnetic field and wherein said top and bottom leads are common to all said sensor stacks; and it that said method further comprises: providing a source of constant current for driving said magnetic sensors; passing said current between said corresponding second ends, thereby generating a magnetic field whose direction is different relative to each of the sensors whereby said sensors generate voltage drops whose magnitudes differ from one another, wherein a voltage drop generated by a sensor is an average of indivudual voltages generated by each said sensor stack; using a differential voltage amplifier to measure said difference in magnitude between said voltage drops; and thereby deriving a value for said electric current.