The equivalent load of an induction hob is strongly dependent on many parameters such as the switching frequency, the excitation level, the size, type and material of the vessel, etc. However, real-time methods with the ability to capture the variation of the load with the excitation level have not been proposed in the literature. This is an essential issue as most of the commercial induction hobs are based on an ac bus voltage arrangement. This paper proposes a method based on a phase sensitive detector that offers an online tracking of the equivalent impedance for this type of arrangements. This algorithm enables advanced control functionalities such as clustering of vessels, material recognition and premature detection of ferromagnetic saturation, among others. After simulation and experimental validation, the method is implemented into a prototype with a system-on-chip (SoC) to verify its real-time behavior. The proposed approach is applied to different real-life situations which prove its great performance and applicability.