A system comprising: at least one coil configured to: generate a first magnetic field having a first frequency that induces a first reflected magnetic field in a conductive target during a first time period, wherein the first reflected magnetic field has a first magnetic field strength; and generate a second magnetic field having a second frequency that induces a second reflected magnetic field in the conductive target during a second time period, wherein the second reflected magnetic field has a second magnetic field strength that is different than the first magnetic field strength; at least one first magnetic field sensing element configured to detect the first magnetic field and the first reflected magnetic field during the first time period and to detect the second magnetic field and the second reflected magnetic field during the second time period; at least one second magnetic field sensing element configured to detect the first magnetic field and the first reflected magnetic field during the first time period and to detect the second magnetic field and the second reflected magnetic field during the second time period; and a processing circuit coupled to receive a respective output signal from the at least one first and at least one second magnetic field sensing elements (406, 408) and calculate an error value of the system. at least one coil configured to: generate a first magnetic field having a first frequency that induces a first reflected magnetic field in a conductive target during a first time period, wherein the first reflected magnetic field has a first magnetic field strength; and generate a second magnetic field having a second frequency that induces a second reflected magnetic field in the conductive target during a second time period, wherein the second reflected magnetic field has a second magnetic field strength that is different than the first magnetic field strength; generate a first magnetic field having a first frequency that induces a first reflected magnetic field in a conductive target during a first time period, wherein the first reflected magnetic field has a first magnetic field strength; and generate a second magnetic field having a second frequency that induces a second reflected magnetic field in the conductive target during a second time period, wherein the second reflected magnetic field has a second magnetic field strength that is different than the first magnetic field strength; at least one first magnetic field sensing element configured to detect the first magnetic field and the first reflected magnetic field during the first time period and to detect the second magnetic field and the second reflected magnetic field during the second time period; at least one second magnetic field sensing element configured to detect the first magnetic field and the first reflected magnetic field during the first time period and to detect the second magnetic field and the second reflected magnetic field during the second time period; and a processing circuit coupled to receive a respective output signal from the at least one first and at least one second magnetic field sensing elements (406, 408) and calculate an error value of the system.