The fluid flows from bottom to top through the meter tube of the flow meter. The float is lifted until an annular gap between the meter ring and the cone-shaped float is produced which corresponds to the flow. The forces acting on the float are in equilibrium. The forces that are mainly acting on the float comprise buoyancy according to the principle of Archimedes,the flow force of the medium and the weight force. Each po-sition of the float corresponds to a flow value measured during calibration, which is transferred to a scale. The BGN variable area flow meter consists of a meter tube with connections, a meter ring, and a conical float. By means of a magnet, the po-sition of the float is transferred to an encapsulated follow magnet, which has been fitted to a pointer axle. The position of a second annular follow magnet fitted on the pointer axle is transferred to the scale by means of the pointer.