Calibration; Purpose Of Calibration; What You Have To Know For Calibration - Mettler Toledo InPro 6850i Bedienungsanleitung

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– Measurement of permanently low oxygen concen-
trations (< 500 ppb in liquids or < 10,000 ppm
[vol.] in gases) in the presence of volatile acidic
components (e.g. carbon dioxide during measure-
ments in breweries) e.g. InPro 6900 i / 6950i:
– 500 mV
Note: To ensure the supply of the correct polarization
voltage the transmitter must be set accordingly.
5.2

Calibration

5.2.1 Purpose of calibration

Each oxygen sensor has its own individual slope and
own individual zero point. Both values are subject
to change, for example, through electrolyte consump-
tion or after exchange of electrolyte or membrane
body. To ensure high measurement accuracy of
the sensor, a calibration must be carried out regular-
ly, but at least after each change of electrolyte or
membrane. Prior to calibration, the sensor has to be
polarized for at least 6 hours.
Please remove the protection cap from the sensor,
rinse the sensor with water and dry it for at least
10 minutes before starting calibration.
To check if your sensor needs a recalibration, you
may dry it and take it in the air to check that the
reading is close to 100 %. If not, then the sensor
needs a new calibration.
With ISM sensors all calibration data are stored in the
sensor.

5.2.2 What you have to know for calibration

Calibration is generally carried out at the polarization
voltage at which measurements are taken.
Zero-point calibration is recommended:
– when measuring less than 5 ppb in liquids
– when measuring less than 125 ppm (by vol.) in
gases
General remarks:
– For calibration in air, the sensor membrane
must be dry, since adhering water drops can
falsify the measured 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.
InPro 6850i, 6900i, 6950i
52 206 349
InPro 6850i / 6900i / 6950i O Sensor 12 / 25 mm
2
© 02 / 09 Mettler-Toledo AG
Printed in Switzerland