The well readable digital tank monitor TCM shows a clear overview of the filling conditions of up to four tanks, e.g. a water, a fuel and a waste water tank. The measuring of liquid level resulted by proven immersion tubes TGT/TGW that are available in different lengths or with ultrasonic sensors series UTV. Older level sensors series TRG or level sensors with different characteristics (240-33 Ohm, 0-90 Ohm,...) can also be connected. Active level sensors with current output 4-20 mA are also connectable. The tank monitor TCM 2 and TCM 4p calculates the water tank level by a flow rate sensor DFS. The calculation of the level is made by a math-integration algorithm. The fill up reset (100%) is made just by pressing a key when the tank is fully. The tank symbols can be choosen individually by the setup. An interval measurement procedure reduces the energy consumption to a minimum. Case the voltage comes under 12 V, the measurement interval increases further reducing the battery consumption.