Abstract: A liquid level sensing apparatus, and related method, that utilizes a tuning fork assembly to detect the presence of not only a liquid or air at a particular location within a container, but also a solid material at that location. The tuning fork assembly includes an excitation transducer and a receiving transducer mechanically coupled to a pair of paddles that are exposed within the container, and a phase-locked loop control system applies an excitation signal to the excitation transducer having a frequency that is regulated to track the tuning fork's resonant frequency. A comparator compares that resonant frequency with a prescribed threshold, to determine whether the tuning fork assembly is disposed in air or a liquid. A failure of the phase-locked loop control system to lock the frequency of the excitation signal at any particular frequency indicates that the tuning fork assembly is over-damped and likely contacted by a solid material.