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Aanderaa 4330 Operating Manual
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Contents
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TD 269 OPERATING MANUALOXYGEN OPTODE 4330, 4831, 4835June 2017page 42 of 93Each batch of sensing foils is delivered with calibration data describing the behaviour with respect tooxygen concentration and temperature. When changing the sensing foil the following 28 coefficients mustbe updated:FoilCoeffA0-13FoilCoeffB0-13These coefficients are found in the Calibration Certificate for the Sensing Foil 3733/4793, refer encloseddocumentation. 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 ina zero-oxygen solution.An air-saturated solution is obtained by inserting freshwater in a glass and bubble it with a standardaquarium 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 airbubbles on the foil. We recommend the zero oxygen solution to be obtained by preparing another glass ofthe same water (as for air saturation) and dissolving 5g of sodium sulphite (Na 2 SO 3) in 500ml water.6.2.2 Calibration Procedure using a Terminal ProgramNOTE! To obtain the highest accuracy the sensor(s) to be calibrated should be submerged into water atleast 24-48 hours prior to the calibration. If a sensor is allowed to dry out this could lead to a bias in thereadings 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 ordinaryaquarium 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 2 gas is also possible, but not recommended, since it isuncertain 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 operatingsystems) or Tera Terminal with the following set-up:9600 Baud8 Data bits1 Stop bitNo ParityXon/Xoff Flow ControlNOTE! Select one of the options ’Sent line ends with line feeds’ or ‘Echo line ends with line feeds’ in theHyper Terminal. |
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