Abstract: A wireless interface probe having a transmitter, a signal transport/measuring device, and a receiver as provided. The transmitter has two sensors: a liquid level sensor and a water level sensor. The liquid level sensor determines the boundary between gaseous and liquid media. The water level sensor detects the presence of conductive liquid such as water. Signals generated by the transmitter sensors are transported inductively to the receiver via the signal transport/measuring device. The signal transport/measuring device is a standard metallic measuring tape which affixes to the transmitter via metallic fasteners. The receiver decodes the signals generated by the transmitter and creates an audio and visual reading output. The output reading indicates to the operator the level of the free-phase hydrocarbons and the level of the water. The difference between the two levels is the thickness of the hydrocarbons, which can be determined by using the measuring tape.