Appendix 7 Multipoint Calibration - Aanderaa 4330 Operating Manual

Appendix 7 Multipoint Calibration

The standard calibration for the oxygen Optodes is based on a common characterization of a production
batch of sensing foils with an additional two-point adjustment for individual Optodes and foils.
For application demanding higher accuracy an individual multipoint calibration is available. The Optodes
are then placed in a temperature regulated bath where the oxygen saturation is changed by diffusing
different mixtures of O2 and N2 into the water. The gas mixture is controlled by use of high accuracy
Mass Flow Controllers. The water is stirred vigorously to provide homogeneity and oxygen concentration
is referenced to three reference sensors that are calibrated with respect to high quality Winkler titrations.
For a standard multipoint calibration the oxygen is changed from 0 to 120% air saturation in 10 steps, and
temperature from 1 to 30 °C in 4 steps, resulting in 40 individual calibration points. Based on these data 7
coefficients (c0 to c6) in the modified Stern-Volmer formula derived by Uchida et al, 2008 [17] is
calculated:
and:
where t is temperature (°C) and P
After the calibration sequence the performance of all sensors are verified in 20 points covering the
complete calibration range.
Note that the multipoint calibration is only available for the 4330 and 4831 Optode and that in order to
enable of use of the above formula the property called Enable SVUformula must be set to "yes" (requires
firmware version 4.4.8 or higher).
TD 269 OPERATING MANUAL
OXYGEN OPTODE 4330, 4831, 4835
June 2017
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