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To fill:
• Check that the membrane head is correctly and securely fastened
Check the membrane for damage
• Unscrew the lock plug from the refill opening
• Fill pipette with KOH
• First fill membrane cap up to half, then tighten securely, rinse any excess KOH
• Then carefully and slowly fill the sensor, then tap against the shaft and tilt the sensor to
re m o v e t h e a i r b u b b l e s . T h e s e n s o r h o l d s a m a x i m u m o f a p p ro x . 5 m l .
• Once no more air bubbles are released and the refill opening is filled, tighten with the lock plug.
• Rinse any excess KOH
• Turn sensor with membrane upwards: Are there air bubbles noticeable under the membrane? If
Yes: Then fill to the top.
• Wait approx. 2 hours - then calibrate – the sensor evaluation should return a 100 % value.
8. Instructions for oxygen measurement
The following should be taken into account when measuring dissolved oxygen:
• Remove the storage flask prior to the measurement.
• The sensor must have been calibrated first.
• The sensor and the liquid to be measured must be at the same temperature
(compare temperatures)
• The sensor must be immersed at least 3 cm into the liquid to be measured
• Measurements are only sufficiently accurate with a minimum flow velocity of approx. 30
cm/sec: This is done by permanently stirring the liquid or using an appropriate stirring
device!
• The measurement is sensitive to shock!
For this reason, it is important to make sure when stirring the liquid that the sensor does not
bang against the container which could otherwise significantly affect the measurement value.
- The optimum operating position is when the sensor opening is facing downwards.
The oxygen's partial pressure, the oxygen concentration [mg/l] and the oxygen saturation [%]
is calculated from the sensor signal and temperature. The measurement is based on water
vapor-saturated air in accordance with DIN38408-C22.
8.1 Salinity correction ('SAL')
With increasing amounts of salt (salinity), the dissolving properties of oxygen in water reduce,
i.e. at the same oxygen partial pressure, less mg of oxygen dissolves in each liter of water.
To calculate the oxygen concentration, the first step is to enter the salinity of the medium
(see 'Device configuration'). The salinity correction is based on fluid media that have an
equivalent chemical composition to sea water. The correction is based on the "International
Oceanographic Tables" (IOT).
44
SD_310_1 10/2015
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