Hanna Instruments edge DO, Инструкция по эксплуатации, Страница: 26 / 36

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Salinity and Altitude Compensation
Temperature, altitude and salinity compensation are used for DO 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
edge
® DO
. 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 influenced by the amount of salt the water contains. Seawater
typically has a salinity of 35 g/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 effect on % oxygen solubility range.
When water is fresh (no sea water), the concentration of oxygen will be at a maximum. The solubility
of the oxygen dissolved in water is decreased when water is brackish or seawater. The solubility of
oxygen in water is decreased when measurements are made at elevations above sea level.
DISSOLVED OXYGEN CALIBRATION
Before proceeding with the calibration, make sure the probe is ready for measurements (see
page 23), i.e. the membrane cap is filled with electrolyte, the probe is connected to the meter and
properly polarized. For an accurate calibration, it is recommended to wait at least 15 minutes to
ensure conditioning of the probe. Keep the protective cap on during polarization time and remove it
for calibration and measurements. Follow the calibration procedure.
OPERA
TIONAL GUIDE