Sonic liquid level measuring apparatus

Claim 1

Apparatus for measuring the level of the top surface of liquid in a tank, of the type comprising a first elongated vibration propagating body that extends downwardly in the tank from near its top, exciter means coupled to said body for recurrently imparting an excitation impulse to it that produces sonic vibration in it, at least one other elongated vibration propagating body extending down into the tank from near its top, detector means coupled to said other body for producing electrical signals in response to vibrations propagated through said other body from the exciter means and by way of the first body, and calculating means connected with said exciter means and said detector means for calculating liquid level in the tank as a function of time required for propagation of vibrations from the exciter means to the detector means, said apparatus being characterized by: A. a plurality of elongated bridging members extending transversely to said bodies and each connected to both of said bodies, said bridging members being fixed to said Bodies at lengthwise spaced intervals along them and being of substantially rigid material that propagates vibration so that as a result of each excitation of the first body, the detector means, during a time thereafter, receives successive periods of vibration, one transmitted through each of said bridging members and a final one transmitted through the liquid; and B. the calculating means comprising 1. means for counting the number of periods of vibration received by the detector means following each excitation impulse, 2. means for recording the time elapsed between receipt by the receiver of the last and the second-last of such periods of vibration, and 3. means for presenting an output representing a distance which corresponds to said number minus one plus a function of said elapsed time, and which output denotes said level.