Method for recognizing and/or assessment of device and/or process related disturbances in a measurement signal

A method for recognizing and/or assessment of device and/or process related disturbances in a measurement signal, especially in a turbidity measurement of a fluid or gaseous medium with the steps of: generation of transmittable signals by means of at least one transmitter, wherein the transmitted signal is transformed through interaction with the medium, depending on the measurement variable, collection of measurement signals by means of at least one of the collectors assigned to the transmitter from the transformed transmission signals, characterized in that, the measurement signals are further processed by generating a distortion ratio of the measurement signal by processing the measurement signal with a distortion factor acquired from a dimensional reduction technique, especially principal component analysis (PCA), wherein the distortion factor takes into account the principal components with the largest contribution to the total variance, and assessing the distortion ratio over the course of time.