VORRICHTUNG ZUR FESTSTELLUNG UND/ODER UEBERWACHUNG EINES VORBESTIMMTEN FUELLSTANDES IN EINEM BEHAELTER

摘要

The device has at least two vibration rods secured at a distance apart to a diaphragm, the edge of which is connected to a screw-in member. A clamping screw is secured to the diaphragm on the side away from the clamping rods tightly enough for the clamping screw and the diaphragm to adopt a position in which the axes of symmetry coincide. The clamping screw is surrounded by a stack of annular piezoelectric elements, electrodes and insulating rings. The stack forms the excitation and reception converter of the device. The stacked excitation and reception converter is clamped and secured between the diaphragm and a hexagon nut. The stack is supported by means of the terminating metal ring on a shoulder surrounding the diaphragm and positioned at a distance from it. The clamping force is selected so that the diaphragm is prestressed to a concave shape at the same time. The excitation converter excites the vibration rods to vibrate at their natural resonant frequency transversely to their longitudinal axes. The reception converter detects a change in the vibration behaviour of the vibration rods and use is made of this to determine and/or monitor the predetermined level. The change in both the vibration frequency and vibration amplitude of the vibration rods may be taken into account.