Robust case with wall thickness of 5 mm either in seawater resistant aluminum or in stainless steel - shaft in stainless steel - rotating components with permanent magnet in front chamber - electronic circuit with ASiC and Hall elements and interface components fitted within main chamber, separated from rotating components by a metallic wall - integrated absolute multiturn gearbox for the acquisition of revolutions - optional potting against water jets (IP 69K) - electrical connections via round plug M12x1 or lead exit.