Dissolved oxygen portable meters are available with either Clark-Type Polarograhic, Galvanic and Optical technologies. Each has their benefits with regards to measurement and maintenance. Portable DO meters are available with automatic or manual calibration, automatic or manual input altitude (barometric pressure) compensation and manual input of salinity for compensation. Meters are available with built-in BOD algorithm for calculating the BOD after two measurements, taken 5 days apart, are made.