A system for determining a location and an orientation of a wire, the system comprising: a test instrument having a single main body and a sensor array comprised of a plurality of sensors (S1, S2, S3, S4, S5, S6, S7, S8) situated within the single main body of the test instrument at a respective plurality of locations on the back of the test instrument, wherein each sensor in the plurality of sensors is situated spatially separate from the other sensors in the plurality of sensors, and wherein when the back of the test instrument is placed near the wire (305, 306, 307, 405, 406, 407, 505, 506) the sensors (S1, S2, S3, S4, S5, S6, S7, S8) within the test instrument are configured to sense a strength of a magnetic field induced by a signal in the wire (305, 306, 307, 308, 405, 406, 407, 505, 506) at the respective plurality of locations; a processor (650, 802) in the test instrument configured to determine the location and orientation of the wire relative to the plurality of sensors based upon the sensed strength of the magnetic field at the plurality of locations of the sensors and provide the determined location and orientation of the wire to a user, wherein the determined location and orientation are indicative of both a position of the wire and an angular orientation of the wire with respect to the respective locations of the plurality of sensors; a memory configured to store readings at each of the plurality of sensors for a plurality of locations and orientations of a test wire relative to the plurality of sensors; and a display configured to graphically display both the sensor array and the wire, wherein the sensor array is shown on the display and the wire is graphically displayed on the display relative to the sensor array based on the determined location and orientation of the wire relative to the respective locations of the plurality of sensors in the sensor array; characterised in that: the processor is further configured to compare the sensed strength of the magnetic field at the plurality of locations with readings previously stored in the memory to determine the location and orientation of the wire based on the comparison with the stored readings. a test instrument having a single main body and a sensor array comprised of a plurality of sensors (S1, S2, S3, S4, S5, S6, S7, S8) situated within the single main body of the test instrument at a respective plurality of locations on the back of the test instrument, wherein each sensor in the plurality of sensors is situated spatially separate from the other sensors in the plurality of sensors, and wherein when the back of the test instrument is placed near the wire (305, 306, 307, 405, 406, 407, 505, 506) the sensors (S1, S2, S3, S4, S5, S6, S7, S8) within the test instrument are configured to sense a strength of a magnetic field induced by a signal in the wire (305, 306, 307, 308, 405, 406, 407, 505, 506) at the respective plurality of locations; a processor (650, 802) in the test instrument configured to determine the location and orientation of the wire relative to the plurality of sensors based upon the sensed strength of the magnetic field at the plurality of locations of the sensors and provide the determined location and orientation of the wire to a user, wherein the determined location and orientation are indicative of both a position of the wire and an angular orientation of the wire with respect to the respective locations of the plurality of sensors; a memory configured to store readings at each of the plurality of sensors for a plurality of locations and orientations of a test wire relative to the plurality of sensors; and a display configured to graphically display both the sensor array and the wire, wherein the sensor array is shown on the display and the wire is graphically displayed on the display relative to the sensor array based on the determined location and orientation of the wire relative to the respective locations of the plurality of sensors in the sensor array; characterised in that: the processor is further configured to compare the sensed strength of the magnetic field at the plurality of locations with readings previously stored in the memory to determine the location and orientation of the wire based on the comparison with the stored readings.