
Transmitter M400 48
© 02 / 2010 Mettler-Toledo AG, CH-8606 Greifensee, Switzerland Transmitter M400
Printed in Switzerland 52 121 378
7.3.3 Process calibration
Enter Conductivity Sensor Calibration mode as described in section 7.1 “Enter Calibration Mode”
and choose one of the compensation modes (see section 7.3 “Conductivity calibration for in-
ductive sensors”).
Select Process and press [ENTER].
Take a sample and press the [ENTER] key again to store the current measuring value.
During the ongoing calibration process, ”A” is blinking in the display.
After determining the conductivity value of the sample, press the [CAL] key again to proceed
with the calibration.
Enter the conductivity value of the sample, then press the [ENTER] key to start the calculation of
calibration results.
After a successful calibration, the calibration values are taken over (Adjust) or discarded (Cali-
brate) or (Abort).
If ”Adjust” is chosen, the message ”Calibration successful” is displayed. The M400 returns to the
measuring mode.
7.4 Calibration of amperometric oxygen sensors
Oxygen calibration for amperometric sensors is performed as either a one-point or process cali-
bration.
h
NOTE: Before air calibration, for highest accuracy, enter the barometric pressure and relative hu-
midity, as described in section 8.2.3.4 “Oxygen parameters”.
7.4.1 One-point calibration for amperometric oxygen
sensors
Enter Oxygen calibration mode as described in section 7.1 “Enter Calibration Mode”.
A one-point calibration of oxygen sensors is always either a one point slope (i.e. with air) or a
zero (offset) calibration. A one point slope calibration is done in air and a one point offset cali-
bration is done at 0 ppb oxygen. A one-point zero dissolved oxygen calibration is available but
not normally recommended since zero oxygen is very hard to achieve. A zero-point calibration is
only recommended if high accuracy at low oxygen level (below 5% air) is needed.
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