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4 Calibration of the Digox 6
4.1 Introduction
During measurement in the liquid samples, the
electrochemically active surface of the electrode
system may change. By this, the sensitivity of the
measuring electrode will change as well.
Therefore, the electrode system needs to be
calibrated from time to time.
The
Digox 6
has a built-in process regulated
calibration system, which can carry out a
calibration without interrupting the measuring
series.
For the
Thiedig active calibration
and the short
calibration, a defined increase of the oxygen
concentration is produced. This is done by
electrolysis of the sample. The resulting increase
of the measuring current is used to determine the
calibration function. With the essential requirement
"no oxygen – no measuring current“ the processor
places this function through the zero point (Figure:
4.1.)
The Thiedig active calibration lasts about 120
seconds. During the actual calibration, the
measuring conditions are also being monitored.
The
short calibration
operates similar to the
Thiedig active calibration, however, it does not
compare the values of measuring current, flow
and temperature with those of the beginning.
It lasts about 60 seconds.
Cross-sensibilities can be eliminated with the
reference calibration
. For this, two defined
oxygen concentrations Ref min and Ref max must
be set. The calibration line is crossing those two
points.
The reference calibration takes into account all
conditions deviating from the ideal case (the
function crosses the zero point) (Figure: 4.1).
Figure: 4.1
Summary of Contents for Digox 6
Page 1: ...Operating Manual Oxygen Analyser...
Page 7: ...7...
Page 11: ...11 Figure 1 3 1 Display 2 Sample supply In Figure 1 4 1 6 1 2...
Page 13: ...13 Notes...
Page 45: ...45 Notes...
Page 57: ...57 10 5 Menu overview...
Page 59: ...59 Notes...
