A fill level measuring device for the microwave-based detection of the fill level of a filling material in a container, featuring - an electronic unit, which is configured to generate transmission signals and to process echo signals; - a transmitter/receiver unit connected to the electronic unit, which is configured to send the transmission signals toward the filling material in the container and to receive the echo signals; and - an electrically conductive probe connected to the transmitter/receiver unit, which protrudes into the filling material and serves to forward the transmission signals and the echo signals, wherein the transmitter/receiver unit sends transmission signals along the probe toward the filling material in a measuring mode, wherein reflection of the transmission signals at a surface of the filling material generates a filling material echo signal, which is fed back along the probe to the transmitter/receiver unit and is transmitted to the electronic unit so that the electronic unit can detect the fill level of the filling material from the filling material echo signal, characterized in that the fill level measuring device features a cable, wherein the electronic unit is connected to the transmitter/receiver unit using the cable and the cable serves to forward the transmission and echo signals, the fill level measuring device features at least one reflection point arranged outside the container, said reflection point generating a reflection point echo signal through reflection of the transmission signal, and the cable which features the at least one reflection point, and wherein the electronic unit performs in-line calibration and/or verification of the filling material echo signal using the at least one reflection point echo signal. - an electronic unit, which is configured to generate transmission signals and to process echo signals; - a transmitter/receiver unit connected to the electronic unit, which is configured to send the transmission signals toward the filling material in the container and to receive the echo signals; and - an electrically conductive probe connected to the transmitter/receiver unit, which protrudes into the filling material and serves to forward the transmission signals and the echo signals, wherein the transmitter/receiver unit sends transmission signals along the probe toward the filling material in a measuring mode, wherein reflection of the transmission signals at a surface of the filling material generates a filling material echo signal, which is fed back along the probe to the transmitter/receiver unit and is transmitted to the electronic unit so that the electronic unit can detect the fill level of the filling material from the filling material echo signal, characterized in that the fill level measuring device features a cable, wherein the electronic unit is connected to the transmitter/receiver unit using the cable and the cable serves to forward the transmission and echo signals, the fill level measuring device features at least one reflection point arranged outside the container, said reflection point generating a reflection point echo signal through reflection of the transmission signal, and the cable which features the at least one reflection point, and wherein the electronic unit performs in-line calibration and/or verification of the filling material echo signal using the at least one reflection point echo signal.