A fill level measuring device for measuring a fill level of a container including a fill level measuring circuit that measures a filling level of a container, at least one transmitter/receiver that communicates with data processing circuitry, at least one fastener that fastens the fill level measuring device to a surface of the container, at least one monitoring circuit that monitors a fastening of the fill level measuring device to the container by the at least one fastener, the monitoring circuit further transmits an alarm message to the data processing circuitry via the transmitter/receiver when the monitoring circuit detects a loosening of the fastening of the fill level measuring device from the container.