A method for start-up of a measuring device, which is embodied to monitor by means of at least one measuring transducer in contact with the interior of a process container, especially of a single-use container, a measured variable of a medium contained in the process container, wherein, for ascertaining a measured value, at least one measurement signal of the measuring transducer is mapped to a measured value of the measured variable according to a predetermined characteristic curve, wherein the method includes: introducing a process medium into the process container; bringing the measuring transducer in contact with the process medium; and performing a one-point calibrating of the measuring device based on a measurement signal registered by the measuring transducer in the process medium or a measured value derived therefrom based on the characteristic curve.