Hanna Instruments HI931 - pH Calibration Procedure

7-10
pH MODE
7.2.13. STIRRING SPEED
Option: 200 to 2500 RPM
7.3. pH CALIBRATION
Calibrate the instrument often, especially if high accuracy is required.
The instrument should be recalibrated:
• Whenever the pH electrode is replaced.
• At least once a week.
• After testing aggressive chemicals.
• When “No pH Calibration” or “pH Calibration Expired” message appears on the display.