Dissolved oxygen measurement mode Users can choose mg/L (ppm) O2 or % % dissolved oxygen with percentage saturation, can choose 1 or 2 point calibration for zero point calibration or 100% automatic calibration in air, and can choose automatic compensation for altitude (up to 4000 m) and salinity (up to 40 g/L) when measuring. Spectral dissolved oxygen built-in temperature sensor provides automatic temperature compensation, automatic interval storage 8000 measurement data memory, through the USB data interface can be stored data to the computer for further data analysis and management.