Vortex flow meter and method for testing a vortex flow meter

A method for testing a piezo element of a vortex flow meter, the method comprising:

• providing the vortex flow meter, including:
• a measuring tube for guiding the medium with a measuring tube wall and a measuring tube lumen formed by the measuring tube wall, wherein the measuring tube wall has an opening;
• a bluff body arranged in the measuring tube;
• a sensor device designed to detect flow vortices caused by the bluff body, the sensor device including a paddle, a sensor main body, and a piezo element, wherein the sensor main body is arranged in the opening and seals media-tight with the measuring tube wall, wherein the paddle projects into the measuring tube lumen and is designed to be deflected by flow vortices from a force-free resting position, and wherein the piezo element is arranged on a rear side of the sensor main body facing away from the measuring tube and is designed to detect deformations of the sensor main body caused by deflections of the paddle and to convert the deformations into an electrical measurement signal;
• and
• an electronic operating circuit designed to detect and evaluate the measurement signal via an evaluation circuit and to provide flow measurement values,
• wherein the electronic operating circuit includes a measuring circuit including an operational amplifier having an inverting input, a non-inverting input and an output, and further includes a first capacitor,
• wherein the first capacitor forms a feedback between the output and the inverting input or the non-inverting input, wherein the respective input is a measurement input,
• wherein the respective other input is a reference input and can be supplied with a first reference voltage, and wherein the output is connected to the evaluation circuit of the electronic operating circuit,
• wherein the piezo element can be supplied with a second reference voltage on a side facing away from the operational amplifier, which is equal to the first reference voltage,
• wherein the measuring circuit further includes a first switch having a first position and a second position,
• wherein the electronic operating circuit is designed to connect the piezo element via the first position of the first switch to the measurement input of the operational amplifier and to charge the piezo element with a first charging voltage via the second position of the first switch, and
• wherein the electronic operating circuit is further designed to derive via the evaluation circuit from a discharge process of the piezo element an information relating to a state of the piezo element, and/or an electrical connection of the piezo element to the electronic operating circuit, and/or a mechanical connection to the sensor main body;
• switching the first switch from its first position to its second position to charge the piezo element;
• switching the first switch to its first position after charging the piezo element to discharge the piezo element;
• and
• detecting the discharge process via the electronic operating circuit and deriving an information relating to a state of the piezo element and/or an electrical connection of the piezo element from a discharge measurement signal.