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Salinity

Pressure

Calibration

Electrochemical sensors are more prone to drift and require more frequent calibrations than optical sensors. In principle, teady-state galvanic and polarographic sensors need calibration daily when in use. If the measurements, however, are reliable also with less frequent calibrations, calibration frequency can be reduced.

Optical sensors are more stable than traditional electrochemical sensors. It has been shown that optical sensors can hold their calibration for months. It is still recommended to calibrate the sensor regularly to obtain most correct measurements. The calibration is done by measuring known sample and comparing the measured value to the known real value.

Three main methods for calibrating DO sensor are

• Winkler titration
• Air-saturated water
• Water-saturated air

References