Calibration statistics
Sensor Current % Last cal. Drift Temperature
64.80 nA 118.8 % 19.6 Count 18.013 C
“% of last calibration” is given by (new cal/old cal) x100 and gives a measure of ageing of the membrane
and the electrode. Sensor drift is automatically checked by the probe and is compared against pre-
defined limits. If excessive drift is detected, this message appears:
Oxygen sensor error, see Operator’s Manual
Please proceed with the maintenance procedures, as illustrated in the probe maintenance section. If the
last message does not appear, it means that the calibration procedure can continue, and the atmospheric
pressure coefficient should be entered:
Oxygen correction coefficient for
1 - Barometric pressure deviation from the 760 mmHg
2 - Stirring effect on the sensor
Enter Altitude above sea level [m]:0
If the atmospheric pressure is 760 mmHg (sea level) and no correction is required, leave the shown
coefficient (0); the probe will propose a correction coefficient of 1.0. If a value different from 0 is entered,
the probe calculates the correction coefficient by itself and then propose it to the operator for approval.
coefficient = 1.0
At the end of this procedure, the programme shows the "Calibration menu".
NOTE REGARDING VARIATIONS IN BAROMETRIC PRESSURE (ALTITUDE) AND THE
SENSOR MEMBRANE COEFFICIENT ALSO CALLED “STIRRING EFFECT”
The correction coefficient different from the nominal one 1.0 is needed for the following reasons:
1) To enter barometric pressure values differing from the 760 mmHg standard which represents the
nominal B.P. at sea level. For example, if the measurements to be made are carried out in an area
which is at 1.340 metres above sea level, then the nominal local barometric pressure is only 655
mmHg. In this case, the correction coefficient is given by the formula:
Local nominal B.P.
Correction Coefficient = ------------------------------
Standard nominal B.P.
2) To correct (if considerable) the possible differences in readings from the gaseous phase (calibration)
and the liquid measurements due to the oxygen consumption of the sensor during measurements.
3) If both of the above coefficients 1) and 2) are simultaneously requested, then the two relevant
correction coefficients must be multiplied together to obtain the correction coefficient to be entered.
4) To expand the scale of the oxygen sensor readings. For example, on entering a correction coefficient
of 10, the readout will be multiplied by a factor of 10.
5) In case of moored applications, where the probe remains steady measuring for long periods, the
coefficient 1.05 should be entered to compensate for the stirring effect on the surface membrane.
For instance, to apply a double compensation due to the barometric effect and to the oxygen
depletion, the following operation must be used
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