A test fixture includes an outer conductor and an inner conductor disposed within and electrically isolated from the outer conductor. The inner conductor includes a top portion having a first diameter, a bottom portion having a second diameter, and a third portion proximate the bottom portion that has a third diameter that is less than the second diameter and is greater than the first diameter. An electrical property of a chamber component disposed within the outer conductor is measurable based on application of a signal to at least one of the outer conductor or the inner conductor.