Fuel-cladding interaction for pressurized water reactors is of interest to the nuclear energy community because of its impact on fuel safety and performance. The complex behavior of fuel-cladding mechanical interaction can result in diameter changes of the cladding. These can be due to internal pressure changes due to fission gas release or fuel pressing directly on the cladding due to fuel swelling. Regardless of the cause of diameter changes, an accurate diameter measurement of the cladding can provide detailed information about the conditions of the fuel and cladding. Other efforts have been made to perform cladding diameter measurements, but contact method have been used with limited applicability to many tests [1]. Electrical impedance based instrumentation is class of measurements that is based on “interrogating” a sensor by providing a current and measuring the voltage (or vise versa) across a system. The parameter of interest is determined by relating it to the measured impedance (calculated from the current and voltage) through the use of an analytic, empirical, or numerical model. These systems are used for a wide variety of measurands in the nuclear industry. They are attractive for in-pile applications because of the potential to be robust to irradiation.