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

18
– Measurement of permanently low oxygen con-
centrations (< 500 ppb in liquids or < 10,000
ppm [vol.] in gases) in the presence of volatile
acidic components (e.g. carbon dioxide during
measurements in breweries) e.g. InPro 6900 i /
6950 i: – 500 mV
h
Note: To ensure the supply of the correct polari-
za tion voltage the transmitter must be set accord-
ingly.
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
consumption or after exchange of electrolyte or
membrane body. To ensure high measurement accu-
racy of the sensor, a calibration must be carried out
regularly, but at least after each change of electrolyte
or membrane. Prior to calibration, the sensor has to
be polarized for at least 6 hours.
a
Please remove the protection cap from the sensor,
rinse the sensor with water and dry it for at least
10 minutes before starting calibration.
h
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
h
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
m edium, the calibration medium must be in
equilibrium with the air. Oxygen exchange
b etween water and air is only very slow. There-
fore it takes quite long time until water is satu-
rated with atmospheric oxygen.
InPro 6850 i / 6900 i / 6950 i
52 206 349
InPro 6850 i / 6900 i / 6950 i O Sensor 12 / 25 mm
2
© 04 / 13 Mettler-Toledo AG
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