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In order to maintain optimum accuracy it is recommended that user select the sampling frequency
required for the application and to not over sample in order to minimize potential drift. Annual recalibration
is optimal and recommended by the factory (refer next section) although for many applications this may
not be possible. In case where longer calibration intervals are expected use of a controlled reference can
be adequate to QC the data.
Figure 6-2 Normalized aging effect versus number of excitations
The standard foil is equipped with a black optical isolation layer to protect it from ambient light. The fast
response foil is not equipped with this layer and is therefore more susceptible to bleaching from external
light. While stored all foils and Optode must be shielded from ambient light. Optodes equipped with the
fast response foil will normally require more frequent calibration but this is highly dependent on the
amount of ambient light.
When saturated with moisture the polymer of the sensing foil will swell a little. This will cause a minor,
approximately 2%, change in the response of the Optode. For optimum accuracy the foils should be
wetted for 48 hours prior to use. The protecting cap supplied with the 4330 and 4831 style Optodes can
be used for keeping the foil both wet and shielded from ambient light.
NOTE! It is not recommended to change standard foils (with the black isolation layer) unless they have
serious mechanical damages. Faster response transparent foils can be bleached by light therefore these
foils require greater care in handling and application. Indications for when you will need replace an
otherwise undamaged foils are:
•
Increasing levels of mesausrement noise
•
TCPhase(deg) vales below 10
AADI Service department can perform a cost-effective performance check and recalibration. Please fill
out our Service Order Form, form no. 135, for this purpose (refer Services page at www.aanderaa.com)
TD 269 OPERATING MANUAL
OXYGEN OPTODE 4330, 4831, 4835
June 2017
page 36 of 93
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