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Each batch of sensing foils is delivered with calibration data describing the behaviour with respect to
oxygen concentration and temperature. When changing the sensing foil the following 28 coefficients must
be updated:
FoilCoeffA
0-13
FoilCoeffB
0-13
These coefficients are found in the Calibration Certificate for the Sensing Foil 3733/4793, refer enclosed
documentation. Refer chapter 6.2.2 for changing foil coefficients.
In addition to the above mentioned coefficient update at a minimum a two point calibration must be done.
This calibration compensates for individual sensor and foil variations.
Two controlled oxygen concentrations are relatively easy to obtain, one in air saturated water, and one in
a zero-oxygen solution.
An air-saturated solution is obtained by inserting freshwater in a glass and bubble it with a standard
aquarium pump. For a more efficient bubbling it is recommended to use an air stone bubble dispenser.
The water should be allowed to achieve temperature stability for at least 1 hour. Take care to not have air
bubbles on the foil. We recommend the zero oxygen solution to be obtained by preparing another glass of
the same water (as for air saturation) and dissolving 5g of sodium sulphite (Na
6.2.2 Calibration Procedure using a Terminal Program
NOTE! To obtain the highest accuracy the sensor(s) to be calibrated should be submerged into water at
least 24-48 hours prior to the calibration. If a sensor is allowed to dry out this could lead to a bias in the
readings of up to 2 %. This effect disappears when the sensor is submerged into the water.
Prepare a suitable container with freshwater. Aerate (apply bubbling) to the water using an ordinary
aquarium pump together with an air stone, and let the temperature stabilize (might take hours).
Prepare a zero oxygen solution by dissolving 5 grams of sodium sulphite (Na2SO3) in 500 ml of water.
Other substances that remove oxygen can also be used.
NOTE! Stripping of the oxygen with e.g. N
uncertain when and if ever an absolute zero oxygen level is/can be reached using this method.
Connect the sensor to a PC by use of the Sensor Cable 3855 (see above RS232 communication).
Start a terminal program, i.e. the HyperTerminal by Hilgraeve Inc (included in Microsoft operating
systems) or Tera Terminal with the following set-up:
9600 Baud
8 Data bits
1 Stop bit
No Parity
Xon/Xoff Flow Control
NOTE! Select one of the options 'Sent line ends with line feeds' or 'Echo line ends with line feeds' in the
Hyper Terminal.
TD 269 OPERATING MANUAL
OXYGEN OPTODE 4330, 4831, 4835
June 2017
gas is also possible, but not recommended, since it is
2
page 42 of 93
SO
) in 500ml water.
2
3
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