Thermo Scientific Star Series User Manual page 38

Dissolved Oxygen Technique
It is also the meter's default setting . If the calibration selection in
not been changed, then pressing
calibration . Due to the inherent differences between water-saturated air
and air-saturated water, upon stability, the air standard is set to 102 .3%
saturation .
i . The highest possible accuracy is reached when calibration temperature is
the same as the measuring temperature .
ii . Moisten the sponge or absorbent cloth in the calibration sleeve with
distilled water and insert the probe into the sleeve, but without touching
the water saturated material . For BOD measurements, this calibration can
be performed in a BOD bottle .
iii . For oxygen levels below 1 mg/L, a zero calibration point is often required .
b . denotes calibration performed using a water sample that is 100%
saturated with air . It is the least commonly used calibration method .
c . denotes manual calibration using a water sample with a known
concentration of dissolved oxygen . It can be used to calibrate the sensor to
the value achieved by a Winkler titration .
i . A Winkler calibration involves performing a manual Winkler titration and
then using that sample as a standard . The titration oxygen level result is
entered in a Winkler calibration as the DO standard value . This correlates
the meter input to the Winkler titration . Note, this method is inherently
less accurate due to the possibility of titration errors introduced when the
calibration is set to the titration test results .
d . denotes a zero calibration, which is used for very low level DO
measurements . It is not generally required unless you are making
measurements below 5% Saturation or 0 .5 mg/L .
EN-32
will automatically perform an air
Thermo Scientific Orion Star
has
Series Meter
™