The DO-400 oxygen measuring device impresses with its ergonomic design, dust and water protection according to IP 65/67, and the illuminated display. The oximeter, equipped with a maintenance-friendly galvanic sensor, is a practical entry-level device that allows for direct reading of concentration in mg/l (ppm) as well as saturation in percent without the need for tables. Calibration is performed with a simple button press using ambient air. For field use in bodies of water, the use of a DOP-401/DOP-402 protective cap is recommended to protect the membrane. Applications include: freshwater and seawater aquaristics, aquaculture/fish farming, and monitoring of wells and water bodies.