Procedure designed to measure the turbidity in a medium being measured using an apparatus comprising at least a first emitter and a second emitter and at least a first detector and a second detector, wherein the first emitter and the second emitter are each excited one after the other to generate a light signal directed into the medium being measured, and wherein, on a first propagation path, the light signal passes through the medium being measured to the first detector where it is converted into a first detector signal, and wherein, on a second propagation path, the light signal passes through the medium being measured to the second detector where it is converted into a second detector signal, wherein a turbidity value is determined using the first and the second detector signal, wherein a third detector and a fourth detector are used, wherein the light signal of the first emitter and of the second emitter passes through the medium being measured on a third propagation path and on a fourth propagation, respectively, to reach said third and fourth detector, wherein the third detector converts the light signal into a third detector signal and the fourth detector converts the light signal into a fourth detector signal, and wherein an additional turbidity value is determined from the third and the fourth detector signal, wherein the additional turbidity value is compared against the turbidity value determined from the detector signals of the first detector and of the second detector, in that the solid concentrations corresponding to the turbidity values are determined from the turbidity values, and the difference is formed between the first and the second solid concentration, and wherein the difference of the solid concentrations are compared with a predefined threshold value to verify the plausibility of the turbidity values. at least a first emitter and a second emitter and at least a first detector and a second detector, wherein the first emitter and the second emitter are each excited one after the other to generate a light signal directed into the medium being measured, and wherein, on a first propagation path, the light signal passes through the medium being measured to the first detector where it is converted into a first detector signal, and wherein, on a second propagation path, the light signal passes through the medium being measured to the second detector where it is converted into a second detector signal, wherein a turbidity value is determined using the first and the second detector signal, wherein a third detector and a fourth detector are used, wherein the light signal of the first emitter and of the second emitter passes through the medium being measured on a third propagation path and on a fourth propagation, respectively, to reach said third and fourth detector, wherein the third detector converts the light signal into a third detector signal and the fourth detector converts the light signal into a fourth detector signal, and wherein an additional turbidity value is determined from the third and the fourth detector signal, wherein the additional turbidity value is compared against the turbidity value determined from the detector signals of the first detector and of the second detector, in that the solid concentrations corresponding to the turbidity values are determined from the turbidity values, and the difference is formed between the first and the second solid concentration, and wherein the difference of the solid concentrations are compared with a predefined threshold value to verify the plausibility of the turbidity values.