OTT Hydrolab DS5X - Known Concentration Dissolved Oxygen Calibration

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Operation
Local Barometric Pressure, BP, in mmHG can be estimated using:
If using the local weather bureau BP, remember these numbers are corrected to sea
level. To calculate the uncorrected atmospheric pressure BP’, use on the following
equations:
Local barometric pressure in mbar (BPmbar) can be converted to local barometric
pressure in mmHG (BPmmHg) using:
5. Enter the barometric pressure in millimeters of Mercury (mmHg) at the site using
Hydras 3 LT software or a Surveyor.
4.2.6.2 Known Concentration Dissolved Oxygen Calibration
Note: Calibration of D.O. mg/L also calibrates D.O. % Saturation.
1. Immerse the sensor in a water bath for which the D.O. concentration in mg/L is known
(for instance, by Winkler titration). This calibration method is more difficult to perform
than the saturated-air method but can yield a higher accuracy if the “known" D.O.
concentration is highly accurate.
2. Enter the barometric units (mmHg) using Hydras 3 LT or a Surveyor.
3. Enter the D.O. units in mg/L using Hydras 3 LT or a Surveyor.
Note: If there is a change in barometric pressure after calibration (for instance, if barometric
pressure drops as you move the calibrated Transmitter to a higher elevation for deployment), the
readings for D.O. % Saturation will not be correct. You must enter a new barometric pressure.
However, the readings for D.O. mg/L will be correct regardless of changes in barometric pressure.
BP' = 760– 2.5(A
ft
/100) or BP' = 760 – 2.5(A
m
/30.5)
where:
BP' = Barometric Pressure at altitude
BP = Barometric Pressure at sea level
A
ft
= Altitude in feet
A
m
= Altitude in meters
BP' = BP – 2.5(A
ft
/100) or BP' = BP – 2.5(A
m
/30.5)
where:
BP' = Barometric Pressure at altitude
BP = Barometric Pressure at sea level
A
ft
= Altitude in feet
A
m
= Altitude in meters
BPmmHG = 0.75 x BPmbar