NOVELTY - The device for the determination of the concentrations of components of a biogas mixture (2), comprises tube line (1), an ultrasonic flow rate measurement device, a temperature-measuring unit, and an evaluation unit. The gas mixture flows through the tube line and consists of three components. The speed of sound and the temperature of the flowing gas mixture in the tube line are determined. The evaluation unit determines the concentration of the water vapor as a function of the temperature and the relative humidity of the gas mixture of 100%.    USE - Device for the determination of the concentrations of components of a gas mixture (claimed).    ADVANTAGE - The device ensures effective determination of the concentrations of components of a biogas mixture and reduces the measurement error completely.    DETAILED DESCRIPTION - The device for the determination of the concentrations of components of a biogas mixture (2), comprises tube line (1), an ultrasonic flow rate measurement device, a temperature-measuring unit, and an evaluation unit. The gas mixture flows through the tube line and consists of three components. The speed of sound and the temperature of the flowing gas mixture in the tube line are determined. The evaluation unit determines the concentration of the water vapor as a function of the temperature and the relative humidity of the gas mixture of 100%. The evaluation unit is intended, in which the speed of sound is determined via an ultrasound measurement, and the speed of sound results through evaluation of the ideal gas equation, in which the concentrations of the components of the gas mixture are determined. The concentration of the water vapor is considered with the determination of the concentrations of the two further components. A humidity-measuring unit is intended, in which the relative humidity of the flowing gas mixture in the tube line is measured. A pressure sensor is intended, in which the absolute pressure of the flowing gas mixture in the tube line is determined. The evaluation unit considers the measured absolute pressure with the determination of the concentration of the water vapor in the gas mixture. The tube line acts as a discharge tube for the gas mixture and/or for the biogas. The tube line is arranged in the upper region of a fermenter, into which the biomaterial is filled. The ultrasonic flow rate measurement device is arranged so that the flow velocity of the flowing gas mixture in the tube line is determined according to the Doppler- or the run time difference principle. The evaluation unit determines on the basis of determined concentrations and the molecular weights of the individual components of the gas mixture and/or the biogas, and on the basis of the determined flow velocity of the volume or mass flow of one of the components of the gas mixture and/or the biogas. The evaluation unit of the energy flow and/or the energy production of the biogas is determined and initialized under consideration of the determined concentration of the individual components and the flow velocity of the biogas in the tube line. A display unit is intended, which sends a message, if the energy flow and/or the energy production of the biogas falls below a given minimum limit value. A unit for the production of biogas consists of a number of fermenters. A control/regulation unit is intended, which controls the temperature of each individual fermenter and/or the feeding of each individual fermenter with bulk material. The energy flow and/or the energy production of the biogas reach a constant value. An INDEPENDENT CLAIM is included for a method for the determination of the concentrations of components of a gas mixture.    DESCRIPTION OF DRAWING(S) - The drawing shows a longitudinal cross-section of an ultrasonic flow rate measurement device.    Tube line (1)    Biogas mixture (2)    Assembly support (3)    Ultrasonic sensor (5)    Sensor mounting plate. (6)