Abstract: Methods and apparatus for non-invasive determination of one or more physical properties of a material in a conduit are presented. In one example, the method comprises initiating a vibration on a wall of the conduit at a first location, capturing a response to the vibration at the first location, capturing a response to the vibration at a second location, and determining at least one physical property of the material based on at least one of the captured responses at the first location and the second location.

Abstract: A non-invasive method for measuring the level of filling material in a vessel and for detecting the presence of the filling material in the vessel at a predetermined set point level is based on monitoring the oscillation of the vessel's outside wall that follows an impact load applied to the external surface of the vessel's wall. The method may employ short range level measurement and long range level measurement procedures. The short-range level measurement utilizes the macro-dynamic properties of the oscillating space in the vicinity of the center of the impact. The long-range level measurement utilizes the properties of the transverse elastic waves propagating along the vessel's wall after the impact. The value of the measured level may be determined by a joint evaluation of the output of the short range level measurement procedure and the output of the long range level measurement procedure.