Calibration; Buffer Groups; Selecting A Predefined Buffer Group; Performing A -Point Calibration - Mettler Toledo Education EL20 Mode D'emploi

Operating the pH meter
4.2

Calibration

4.2.1

Buffer groups

The Education Line pH meters allow you to perform - or 2- point calibrations. After selecting your
calibration buffer group from one of the three predefined buffer groups in the meter, the buffers are
automatically recognized and displayed during calibration (auto buffer recognition).
The three predefined groups are:
B .68
B2 2.00
B3 .68
Tables (B...B3) for automatic temperature compensation are programmed in the meter for each buffer
group (see also Appendix).
4.2.2

Selecting a predefined buffer group

Press the Setup key (EL20) or press and hold the Mode/Setup key (EL2) until the setup icon appears on
the display and the MTC temperature blinks. Press Read to ignore – the current temperature unit blinks
– press Read to ignore again. When the current buffer group blinks, the buffers belonging to this buffer
group appear alternating on the display. Use  or  to select another buffer group and press Read to
confirm your selection. The meter will exit automatically to the measurement screen.
4.2.3 Performing a 1-point calibration
Place the electrode in a calibration buffer and press Cal. The calibration icon and the measurement icon
appear on the display. The meter endpoints according to the preselected endpoint mode after the signal
has stabilized or after pressing Read. The relevant buffer value is displayed and stored; the measurement
icon disappears from the display.
To finish the calibration and return to the sample measurement, press Read. The offset value and the
slope are then shown on the display for 3 seconds. To reject the calibration, press Exit before the meter
returns automatically after 3 seconds to the measurement screen.
Note:
With the -point calibration only the offset is adjusted. If the sensor was previously calibrated with muti-
point calibration the previously stored slope will remain. Otherwise theoretical slope (-59.6 mV / pH)
will be used.
4.2.4

Performing a 2-point calibration

• Step : Perform the first calibration as described above in "Performing a -point calibration".
• Step 2: Rinse the electrode with deionized water.
• Step 3: Place the electrode in the next calibration buffer and press Cal
8
Five_pH_edu.indb 8
4.0 7.00 0.0
4.0 7.00 9.2
4.00 6.86 9.8
(at 25°C)
.00 (at 25°C)
2.46 (at 25°C)
METTLER TOLEDO Education Line pH meter
12.03.2007 15:08:47