Aanderaa 4330 Operating Manual page 74

A: Operating 0 to 40°C; Transport -40°C to 70°C, for storage we recommend room temperature or lower.
MR 16
Q: After calibration the maximum reading we can get in air at room temperature is 94.1 instead of 100. Do we need to replace the oxygen sensing foil?
A: The sensing foil does not need to be replaced.
The relative oxygen computed by the Optode is referred to standard atmospheric air pressure (1013.25 hPa).
The lower reading of 94.1 can be caused by that the saturation calibration of the Optode was done in a vial in which there was over saturation (e.g. because
of the pump or because of non-stable temperature see also CCAP9) Another reason can be that your measurement is taken in an environment where the
air pressure is lower than standard air pressure or that the oxygen concentration is lower.
See also question MR1.
You can find more about this topic in the operating manual.
MR 17
Q: Is there a difference in the sensor response if the foil is wet or dry?
A. Yes the sensor is and should be calibrated in a wet environment and it takes hours for the foil to become completely wet or dry.
Taking a sensor which has been sitting in a dry environment for several hours and introducing it into water to make a spot measurement can lead to an error
of maximum 2%.
Keeping the sensor in a humid environment for at least 24 hours will eliminate this error.
If you would like to do spot measurements, where the sensor is out of the water most of the time, we recommend you to keep the sensor in a wet
environment (such as a plastic bag with water) in-between measurements.
MR 18
Q. I have mounted my sensors in chambers.
When I immerge them into the water the response increases dramatically and already at 10m water depth I am measuring about twice the concentrations
compared to what I am measuring at the surface.
What is happening?
A. The most likely explanation is that you have trapped air inside your chambers and that the sensors are measuring in this air.
At 10m water depth the partial pressure of oxygen is two times higher and this is what you are measuring.
MR 19
Q. I have mounted my sensors in chambers to make sediment-water incubations at the bottom.
The oxygen readings looks normal until the chambers are inserted into the sediment and the lids are closed.
Then it looks like, from the response of the Optodes, as if the oxygen concentrations increase.
page 74 of 93
TD 269 OPERATING MANUAL
OXYGEN OPTODE 4330, 4831, 4835
June 2017