| 摘要 |
The device comprises at least two oscillating rods which are attached, at a given distance apart, to a membrane, the edge of which is connected to a screwed piece. On the side of the membrane remote from the oscillating rods, a tensioning screw is ridigly connected to the membrane so that the tensioning screw and the membrane adopt a position relative to each other in which the axes of symmetry coincide. The tensioning screw is surrounded by a pile of annular piezoelectric elements, electrodes and insulating rings. This pile consitutes the exciting and receiving transducer of the device. The transducer is clamped and fastened between the membrane and a hexagonal nut. The pile thus rests on pressure points arranged between the membrane and a metal ring which terminates the pile. The clamping force is chosen so that the membrane is simultaneously pretensioned in a concave shape. The exciting transducer causes the oscillating rods to oscillate at their natural resonance frequency in opposite directions and perpendicular to their longitudinal axes. Any change in the oscillating behaviour of the oscillating rods is detected by the receiving transducer and used to determined and/or monitor the predetermined volume. It is thus possible to exploit both the frequency and the amplitude of oscillation of the oscillating rods. |
