Method of filling level measurement of layered media

A sensor (10) having a transmitter (32) and a receiver (34) for transmitting and receiving an electromagnetic signal, as well as having a control (30) which is configured to determine the filling level of a medium (14) and/or of a second medium (16) in a container (12) with reference to the time of flight of the signal,

• wherein the control (30) is configured to determine the filling level using a method comprising the steps of:
• transmitting an electromagnetic signal in the container (12), and
• recording a signal curve (S) of the electromagnetic signal reflected in the container (12);
• determining a signal time of flight (t) up to a border transition (18, 20) to the first medium (14) and/or up to the second medium (16) with reference to the signal curve (S);
• determining a filling level of the first medium (14) and/or a filling level of the second medium (16) from the signal time of flight (t);
• determining the threshold value (K·IMedium) by a calibration measurement in which only the first medium (14) is located in the container (12) and a threshold value integral (IMedium) of the signal curve (S) is formed in a region of an echo signal (40) at the border transition (18) to the first medium (14);
• and
• recognizing the border transition (18, 20) by a comparison of an integral over the signal curve (IS) with a threshold value (K·IMedium), the integral starting from a reference position (t0).