An apparatus and method for monitoring the liquid/solid interface position of an alloy ingot being formed by either direct chill or electromagnetically enhanced direct chill casting systems comprising an inductive sensor wire disposed about the mold wall of the casting system, driving the sensor wire to cause a magnetic flux to penetrate into the ingot, and sensing the change in the impedance or components of the impedance of the system. Monitoring the liquid/solid interface position allows ready adjustment to operating controls, such as, containment/stirring inductors, cooling systems and casting parameters, thereby producing a desirable ingot.