Tube for a transducer, transducer comprising such a tube, and measuring system formed therewith

A measuring system for measuring at least one flow parameter, which is variable over time, of a fluid flowing in a pipe, the measuring system comprising:

• a transducer configured to detect pressure fluctuations in a Kármán vortex street formed in the flowing fluid, the transducer comprising:
• a tube configured to conduct a fluid flowing through the tube in a predetermined flow direction, the tube comprising:
• a tube wall which defines a lumen of the tube, the tube wall having a maximum wall thickness of more than 1 mm;
• and
• a bluff body disposed within the lumen and connected to an inner side of the tube wall facing the lumen,
• wherein the tube wall comprises two mutually spaced, equally shaped sub-segments, each having a sub-segment wall thickness deviating from the maximum wall thickness by more than 30% of the maximum wall thicknesses and/or by more than 1 mm, and each sub-segment wall thickness being less than 1 mm and/or more than 0.1 mm,
• wherein the two sub-segments include a first sub-segment disposed upstream of the bluff body relative to the flow direction and a second sub-segment disposed downstream of the first sub-segment relative to the flow direction and at least partially downstream of the bluff body,
• wherein the bluff body is configured to induce vortices in the flowing fluid such that the Kármán vortex street is formed in the fluid flowing downstream of the bluff body and along a measuring section defined by the first and second sub-segments of the tube wall;
• a piezoelectric, capacitive or optical first sensor element, which is fixed to the first sub-segment of the tube wall and is configured to detect elastic deformations of the first sub-segment and to convert the detected deformations into a first sensor signal corresponding to the deformations using a voltage and/or an electrical current dependent on the deformations;
• and
• a piezoelectric, capacitive or optical second sensor element, identical to the first sensor element, which is fixed to the second sub-segment of the tube wall and is configured to detect elastic deformations of the second sub-segment and to convert the detected deformations into a second sensor signal corresponding to the deformations using a voltage and/or an electrical current dependent on the deformations,
• wherein the second signal relative to the first signal represents the pressure fluctuations in the Kármán vortex street formed in the flowing fluid;
• and
• a measurement electronics unit configured to receive and process the first sensor signal and the second sensor signal and to generate measurement values representing the at least one flow parameter.