Polarographic Dissolved Oxygen Calibration - Thermo Scientific Orion Star Manual Del Usario

Polarographic Dissolved Oxygen Technique

Polarographic Dissolved Oxygen Calibration

• Prior to calibration, the dissolved oxygen probe must be prepared and polarized .
The probe is continuously polarized when it is connected to the meter . When
the probe is first connected or if the probe is disconnected for more than 60
minutes, connect the probe to the meter, connect the meter to a power source
and wait 30 to 60 minutes for the probe to polarize . Disconnecting the probe for
less than one hour will require 5 to 25 minutes for polarization .
• The meters will supply a polarization current to the dissolved oxygen probe
even when the meter power is off . To maximize the meter battery life, unplug
the probe if it will not be used for an extended period .
1 . Select one of the following calibration modes in the setup menu .
a . – An air calibration is performed in water saturated air using the
calibration sleeve . This is the simplest and most accurate calibration . Due to
the inherent differences between water saturated air and air saturated water,
102 .3% saturation will be displayed when the calibration reading is stable .
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 without touching
the water saturated material . For BOD measurements, this calibration
can be performed in a BOD bottle .
b . – A water calibration is performed using water that is 100% saturated
with air . Bubble air into a water sample and gently stir the sample to prevent
the buildup of air bubbles on the dissolved oxygen probe membrane .
c . – A manual calibration is performed using a water sample with
a known concentration of dissolved oxygen . This method can be used
to calibrate the dissolved oxygen probe to the value achieved by
a Winkler titration .
EN-26 Thermo Scientific Orion Star and Star Plus Meter User Guide
™