Xylem SI Analytics Lab 745 Operating Manual page 25

9.6.2.3 Two point calibration
> You will be prompted to immerse the sensor into the first calibration medium (ambient air).
Confirm this dialog with (ON/OFF). The currently measured values will be displayed.
If the measured values (pH + temperature!) are in a stable condition, reconfirm by pressing
(ON/OFF).
> You will be prompted to enter a nominal value (temperature-corrected buffer value!).
Via (INFO) or (CAL) you select the position to change.
Via (CONF +1) or (LOG -1) you change the position.
(ON/OFF) confirms and saves your setting.
(MEAS) terminates the entry dialog without transferring the value.
> You will be prompted to immerse the sensor into the second calibration medium.
Perform the same steps as with the first calibration solution
9.6.2.4 Automatic calibration
The automatic calibration of the pH measurement is a two point calibration and requires the
knowledge, which buffer solutions you would like to use for the calibration.
The Lab 845 offers the following buffer sets for the calibration:
NBS standard buffering solution as per DIN 19266: pH value at 25 °C 1.68 / 4.01 / 6.86 / 9.18 / 12.45
Technical buffering solution as per DIN 19267:
Merck buffering solution:
Mettler Toledo buffering solution:
> Select the buffer set you would like to use for the calibration.
You will be prompted to immerse the sensor into the first calibration solution.
Confirm this dialog with (ON/OFF). The currently measured values will be displayed.
If the measured values (pH + temperature!) are in a stable condition, reconfirm by pressing
(ON/OFF). The found buffer will be displayed, reconfirm with (ON/OFF).
Immerse the sensor into the second calibration solution.
Perform the same steps as with the first calibration solution.
This completes the calibration process. The new calibration value will be saved in the device.
If the calibration is faulty, an error message will be displayed (see  9.6.2.5).
9.6.2.5 Calibration error
The limits for all calibration values are saved in the meter. If the entered values are outside these
limits, one of the following error messages will be displayed:
"!Incorrect entry!" or "!Calibration error!".
You may have to repeat the calibration, service the sensor or replace it (wear part!).
pH value at 25 °C 1.09 / 3.06 / 4.65 / 6.79 / 9.23
pH value at 20 °C 4.00 / 7.00 / 9.00
pH value at 25 °C 1.679 / 4.003 / 7.002 / 10.013
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