The development of the ECO 51x series focused on the essential functions of measurement technology. Pure measurement with an emphasis on precision, speed, and reliability, all packaged in a compact housing, offers an outstanding price-performance ratio, made in Germany. The handheld devices impress with their ergonomic design, dust and water protection according to IP 65/67, and the illuminated display. The pH meters are a true alternative to pH sticks on one hand and to expensive, complex devices on the other. The ECO 510 measuring device allows for pH measurements. These devices can be used in aquaristics, aquaculture, water monitoring, plant cultivation, agriculture, laboratories, quality assurance, service, and food applications. The three-line LCD display provides ergonomic wide-angle visibility thanks to the backlighting—both day and night. The HOLD function allows for freezing the displayed values. Power is supplied by two powerful AA batteries, and the energy-saving design along with the configurable auto shut-off ensures long operation. The configurable LCD backlighting offers additional energy-saving options. With regular calibration using the recommended GPH-DOS 4/7/10, the device achieves excellent accuracy for its class of instruments.