Abstract: The present disclosure relates to a method for preparing an oil-in-water mixture having a predeterminable oil concentration which can be used as a reference mixture in the determination of oil concentrations of oil-in-water mixtures, comprising the steps of arranging at least one oil storage element in a container, feeding a predeterminable amount of a water-containing fluid into the container; and introducing ultrasonic waves into the fluid that are emitted in the direction of the oil storage element covered by the fluid, wherein the oil received in the oil storage element is released from the oil storage element by means of ultrasonic waves acting on the oil storage element and is distributed in the fluid. The present disclosure further relates to an apparatus for preparing an oil-in-water mixture.

Abstract: The present disclosure relates to a sensor arrangement including a housing, connectable to a process container and including a guiding passageway formed therein, and a sensor body displaceable in the guiding passageway between a first position and a second position, wherein the sensor body has at least one end section, which can be moved out of the housing and which includes at least one sensor element serving for registering a measured variable of a measured medium, wherein the at least one sensor element is arranged in the first position of the sensor body within a chamber formed in the housing and, in the second position of the sensor body, outside of the housing, and wherein the at least one end section of the sensor body has a base and a peripheral surface, wherein the at least one sensor element forms a part of the peripheral surface.