SYSTEM FOR DETECTING A MEASUREMENT VARIABLE OF A FLUID BEING CONDUCTED IN A FLUID-CONDUCTING LINE, FLOW-THROUGH DEVICE FOR ARRANGING ON A FLUID-CONDUCTING LINE AND FOR ATTACHING A FLOWMETER, AND USE OF A FLOW-THROUGH DEVICE

The invention relates to a system for detecting a measurement variable of a fluid being conducted in a fluid-conducting line, said system having: - a flowmeter, in particular an ultrasonic flow meter, for detecting the measurement variable, - a flow-through device (10) for arranging on the fluid-conducting line and for attaching the flowmeter for detecting the measurement variable of the fluid being conducted by the line, said flowmeter having: - a first and second connection (12, 14), by means of which the flow-through device (10) can be connected to the fluid-conducting line, and - a measurement region (16) which is arranged between the first connection (12) and the second connection (14) and which can be coupled to the flowmeter for detecting the measurement variable, wherein the first connection (12), the measurement region (16), and the second connection (14) define a flow path (A) for the fluid through the flow-through device (10), and the measurement region (16) has at least two contact surfaces (20), which extend at least partly along the flow path (A), for contacting the flowmeter. The at least two contact surfaces (20) are designed to separate a coupling means under the effect of a pressing force, and the flowmeter is designed so as to exert at least the pressing force onto the at least two contact surfaces (20) by means of a coupling of the flowmeter to the measurement region (16). The invention additionally relates to a flow-through device and to a use thereof.