Simultaneous Measurements of Wire Diameter and Conductivity Using a Combined Inductive and Capacitive Sensor

Metallic wires are used in many industrial applications, where the diameter and conductivity are key parameters to be measured. In eddy currents testing, the inductance of the sensor is affected by both the diameter and conductivity of sample wire. Consequently, wire diameter and conductivity cannot be determined from a single inductance measurement. In this paper, a novel combined inductive and capacitive sensor is designed, in which the diameter can be inversed from the capacitance measurement of the sensor. Based on the diameter value, the inductance measurement can be used to accurately determine the conductivity of the wires using a look-up table approach. In addition, a model for a wire inside of the capacitive sensor is derived. Measurements have been carried out for 16 samples and the results have verified the proposed approach. This technique could contribute to real-time in-situ quality control of wire + arc additive manufacture processes.