Abstract: A method for calibrating a measuring device monitoring at least one measured variable of a measured medium by means of at least a first sensor, wherein the signal of the first sensor is mapped to a measured value on the basis of a mapping specification, and wherein the method includes the following steps: a current measured value of the measuring device is recorded as current calibration measured value; a laboratory reference sample of the measured medium with the properties of the calibrated measured value at the point in time of the recording is supplied to a laboratory reference measuring device; the actual value of the measured variable is ascertained with the laboratory reference measuring device on the basis of the laboratory reference sample and made available and recorded as current laboratory reference measured value; and, on the basis of the current calibration measured value, as well as the current laboratory reference measured value, the mapping specification is updated, characterized in that at l