Hanna Instruments Edge - Page 69

Operational Guide
69
DO Meter
Conguration
Salinity and Altitude Compensation
Temperature, altitude and salinity compensation are used for dissolved
oxygen concentration measurements (ppm or mg/L). When the water is colder,
it can hold more dissolved oxygen, when it is warmer it holds less oxygen.
Compensation for temperature-related solubility is done automatically using
the built-in temperature sensor within the DO probe and algorithms in the
edge meter. When water is measured at an altitude below sea level, oxygen
solubility increases, but above sea level the oxygen solubility decreases.
To compensate for this during calibration and measurement, the user must
provide the approximate altitude (in meters) in the SETUP menu. The settings
are in 100 m increments; select the value closest to the actual altitude. Some
examples of altitudes around the world follow:
Location Meter Feet
Sebkha paki Tah, Morocco -55 -180
Lake Frome, Australia -6 -20
Netherlands, coastal providence -1 to -7 -3 to -23
Lake Michigan, USA 176 577
Lake Geneva; France, Switzerland 372 1220
Denver, CO USA 1609 5279
Mount Everest 8848 29029
The solubility of oxygen in water is also inuenced by the amount of salt the
water contains. Seawater typically has a salinity of 35g/L and the oxygen
solubility is 18% less compared to fresh water at 25°C. By entering the
approximate salinity value, the calibration and subsequent concentration
measurement will be compensated to display the correct oxygen
concentration. A 18% error would result if the salinity value is not entered.
Note: Salinity and Altitude have no eect on % oxygen solubility range.