Single Point Calibration - Mettler Toledo InPro 6880 i Série Instructions D'utilisation

14
General remarks:
– For calibration in air, the opto-cap must be dry,
since adhering water drops can falsify the mea-
sured oxygen value.
– Make sure that the oxygen saturation index of the
calibration medium is correct and remains
constant during calibration.
– In the event of calibration in water or sample
medium, the calibration medium must be in
equilibrium with the air. Oxygen exchange
between water and air is only very slow. Therefore
it takes quite long time until water is saturated with
atmospheric oxygen.
– Calibration in a fermenter should be performed
after sterilization.
– Make sure that all other parameters, such as
temperature and pressure, are constant.
For continuous applications, we recommend periodic
recalibration in line with your requirements on
accuracy, the type of process in operation and your
own experience. The frequency of the need for re-
calibration depends very much on the specific
application, and therefore appropriate intervals cannot
be exactly defined here.

5.2.3 Single point calibration

For most application, a single point calibration should
be sufficient, as long as not the whole measuring range
of the sensor is used.
To measure high oxygen concentrations with high ac-
curacy e.g. air saturated medium, an air calibration is
recommended.
A process calibration should be done when the sensor
can not be removed from the process.
By carrying out a single point calibration, the factual
phase angle at zero oxygen (phi 0) or phase angle at
hundred percent oxygen (phi 100) of the sensor can
be established.
The calibration medium can be water with known oxy-
gen saturation index (e.g. air-saturated water) or air
with known water-vapor saturation (e.g. water-vapor
saturated air).
After the sensor signal has stabilized, the complete
measuring system can then be calibrated to the 100%
value of the desired measurable variable, e.g. 100%
air, 20.95% O
normal pressure (see instruction manual for the
transmitter).
Single point calibration should be sufficient for almost
all process applications.
InPro 6880 i
52 206 256
InPro 6880 i Series O
, or 8.26 ppm at 25 °C (77 °F) and
2
Sensor 12 mm
2
© 09/07 Mettler-Toledo AG
Printed in Switzerland