Horiba Scientific LAQUAact D-75G, Instruction Manual

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Dissolved oxygen measurement
38
• Performing calibration using the standard solution
If high precision measurement is necessary, perform two-point calibration using the
standard solution.
1. Wash the membrane at the tip of the DO
electrode with pure water (or deionized water)
and wipe it with a soft cloth at least 10 minutes
before calibration.
Be careful not to break the membrane at the tip of
the electrode.
2. Prepare the standard solution to be used for calibration.
・
Preparing the zero standard solution
Add 50 g sodium sulfite (Na
2
SO
3
) into 1000 mL pure water (or deionized water) and
stir until sodium sulfite completely dissolves.
・
Preparing the span standard solution
Use an air pump to bubble pure water (or deionized water) in a container for about
an hour to create oxygen saturated condition.
3. Press the key to enter the calibration mode.
4. Press the key to change to standard solution calibration.
Pressing the key again changes back to air calibration.
5. Perform the 1st point calibration. Immerse at
least 6 cm from the tip of the DO electrode in
the zero standard solution.
In order to immerse the temperature sensor
equipped with the electrode in the standard
solution, immerse it at least 6 cm of the standard
solution.
During measurement, use a stirrer to stir the
standard solution at 1000 rpm to 1500 rpm.
Note
・ If the temperature of the standard solution rises due to the use of a stirrer, use a
temperature controlled bath.
・
When using an electrode "9551-20D" or "9551-100D", immerse at least 9 cm from the tip.
key key