Systems and methods for operating and calibrating electrical parameter measurement devices are provided herein. The devices may include a current sensor that includes a plurality of magnetic field sensors positioned around a measurement area that receive a current carrying conductor under test. The sensor may include a plurality of concentric rings of magnetic field sensors that provide accurate measurements that ignore magnetic fields from conductors or other components outside of the measurement area. The sensors may be used to determine the position of a conductor under test, and such information may be used to produce accurate measurements by accounting for the conductor's position. A calibration system May 10 also be provided that is operative to generate calibration data that is subsequently used to provide more accurate measurements. The calibration data may include one or more lookup tables, coefficients for one or more mathematical formulas, or other types of data.