US Patent 7908920 Velocity-of-propagation fluid level measurement method

An apparatus for determining a level of a liquid in a tank is provided. The apparatus comprises a probe and electronics. The probe passes into the tank and is immersed in the liquid. The probe includes a fiducial in spaced relation with a distal end. The electronics are operably coupled to the probe. The electronics include a signal generator propagating a signal along the probe and a signal receiver receiving the signal propagated along the probe. The electronics determine a velocity of propagation and/or an amount of time for the signal to travel between the fiducial and the distal end. The level of the liquid in the tank is then determined using the velocity of propagation and/or amount of time.