High quality fill level measuring device developed especially for rainwater usage. With the calibration function the system is coordinated to the different tank heights. The fill level is shown in 1% steps by a 3-digit LCD-display. The sensor electronics work with a 12 volt of low current and is reverse polarity protected. It is attached to the main device with a 20 metre long cable. As soon as the calibration and the assembly is completed no further setting up is required.