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Verfügbare Sprachen
Dissolved oxygen measurement
(C302x, C303x, C304x)
Air pressure measurement
(C302x, C303x, C304x)
Principle
(C302x, C303x, C304x)
Interferences
(C302x, C303x, C304x)
5
1. Select the desired mode (ppm)(O
ately show the measured value according to the previous calibration. Should
you want to recalibrate, press CAL.
2. The display shows the salinity correction. Select the proper value and press
OK. Leave salinity correction to zero unless you are going to measure in heavily
salted solutions such as e.g. sea-water (35 g/l). Select [CALIBRATE], press OK
and follow the instructions on the screen until the calibration is finished.
3. The electrode exposed to the air reaches an equilibrium corresponding to the
partial pressure of oxygen and thus to saturation in water at the given temper-
ature. The instrument shows the measured saturation, current, temperature,
and will calibrate automatically when readings are stable.
4. After rinsing the electrodes with distilled water, immerse them in the samples
and read the display. Stirring the solution during the measurements promotes
the homogeneity and is obligatory! The advection rate must be at least 10
cm/s.
5. Rinse the electrode always after use and store it in distilled water.
•
A blinking decimal point warns you for unstable measurements. Wait to read
the display!
•
Stirring the solution during the measurements promotes the homogeneity and
is therefore always recommended.
•
Hold MODE pressed and press ê to change the resolution from 0.1 to 0.01 ppm
or from 1 to 0.1 %.
%O
measurement:
2
1. Select the desired mode (%O
show the measured value.
•
To browse between ppmO
cially.
1. Select the desired mode (hPa) by pressing é ê . Should you want to recalibrate,
press CAL.
2. Select [CALIBRATE], press CAL, adjust to the real air pressure and press OK.
•
Select [RESET] and press OK to reset the calibration.
The oxygen meter and its electrode function according to the Clark principle with
silver as cathode and lead as anode in an electrolyte cell. Oxygen gas present
in the electrolyte is reduced to OH ions at the cathode. The resulting current is
diffusion limited and therefore proportional to the oxygen concentration in the
sample solution. This current is amplified, corrected, and displayed in mg/l, ppm
or % dissolved oxygen.
All substances which can diffuse through the membrane and for which 800 mV poten-
tial suffices for polarographic reduction, will be reduced in the electrode. This will
give a corresponding current contribution, if they are present. Interference can
be caused by ions entering the electrode through porous or mechanically damaged
membranes and by diffusion of other reactive gases apart from oxygen, e.g. CO
Cl
, SO
, and H
S. These substances react in undesired manner with the electrode.
2
2
2
Acidic or basic gases change the pH value of the electrolyte solution and thus dis-
turb the reading, particularly when measuring small oxygen concentrations. High
salt concentrations in the sample solution can falsify readings too.
) by pressing é ê . The display will immedi-
2
) by pressing é ê . The display will immediately
2
, hold MODE pressed and press é sequen-
or %O
2
2
C301x • C302x • C303x • C304x • C305x • C306x
,
2
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