Abstract: The invention is a butterfly valve for a flow duct of an air-conditioning installation. The butterfly valve comprises two butterfly valve faces and is mounted for rotation about an axis. A device with at least two measurement points for determining the volume flow rate of a gaseous medium flowing in the flow duct is provided. In order to specify a butterfly valve, for example for a volume flow rate controller, which can determine a high differential pressure, even at very low volume flow rates, the butterfly valve comprises at least one hollow chamber on each of its two butterfly valve faces. Each hollow chamber has at least one recess, preferably with a multiplicity of recesses formed in the manner of a perforation. One measurement point is associated with one hollow chamber and the other measurement point is associated with the other hollow chamber.

Abstract: The invention is a butterfly valve for a flow duct of an air-conditioning installation. The butterfly valve comprises two butterfly valve faces and is mounted for rotation about an axis. A device with at least two measurement points for determining the volume flow rate of a gaseous medium flowing in the flow duct is provided. In order to specify a butterfly valve, for example for a volume flow rate controller, which can determine a high differential pressure, even at very low volume flow rates, the butterfly valve comprises at least one hollow chamber on each of its two butterfly valve faces. Each hollow chamber has at least one recess, preferably with a multiplicity of recesses formed in the manner of a perforation. One measurement point is associated with one hollow chamber and the other measurement point is associated with the other hollow chamber.

Abstract: A generally closed lab hood having an opening closable by a movable door and connected to a variable-throughput suction source has a vent-control system having a sensor for detecting a velocity of flow of air into the hood and for generating an output corresponding to the detected velocity. A controller connected to the sensor and to the variable-throughput suction source receives the output and operates the suction source to set throughput of the source at a level corresponding to the output so that as the detected velocity increases the throughput of the suction source is increased and vice versa. The controller includes a sensor tube having an inner end opening into the hood and an outer end opening outside the hood and a sensor in the tube for detecting the velocity of air-flow therethrough. This tube is offset from the opening. The controller operates proportionally to set the throughput of the suction source relative to the air-flow velocity.

Abstract: A volume flow controller for air conditioning and ventilation apparatus which has a pivotable flap in a flow duct whose pivot shaft has a lever arm and which is articulated to a spring. To provide a mechanically self-actuating volume flow controller, in which the spring is matched to the control process by a simple adjustment, the spring is a leaf spring whose one end is connected with a lever and whose other end is so fastened on a cam disk that upon adjustment of the cam disk about a rotation point, the leaf spring is entrained by the cam disk and rolls on the curve thereof. A device is provided for fixing the cam disk.