An instrumented tubing for determining a contribution of a given zone to fluid production of a reservoir, the instrumented tubing including a tube having an open end for collecting a fluid flowing from the given zone and a port for coupling the tube to a production tubing for letting the collected fluid flow into the production tubing, and a sensor for measuring a parameter of the collected fluid, wherein the sensor is connected to an electronic unit for determining the contribution of the given zone to the fluid production of the reservoir based on said measured parameter.