Model WQC-30 6.1 Calibration of pH
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6. Calibration
The calibration procedure varies depending on measurement items for pH, turbidity, electrical
conductivity, temperature or dissolved oxygen (option). Because salinity measurement is performed
by converting the electric conductivity measurement value, no calibrating function only for salinity
measurement is provided.
6.1 Calibration of pH
(1) Key points of pH Calibration
(a) The sensitivity of the pH electrodes and the potential of the reference electrodes respectively
vary over time. Periodic calibration of pH, therefore, is necessary.
【
IMPORTANT
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•
Be sure to calibrate pH periodically.
(b) While the calibration frequency may vary with sample and the environment of measurement,
usually once a day is recommended.
(c) The calibration procedures listed below are available. Usually, follow the two-point pH
calibration procedure which uses a standard pH solution.
Types of pH Measurement and Calibration Procedures
Types of Measurement
Calibration
Procedures
Standard pH solution to be used
Reference
Normal measurement
Two-point
pH
calibration
pH 6.86 standard solution, pH
4.01 (or pH 9.18) standard
solution
“6.1 (2) pH Calibration
Procedure”
Check for measured
value near neutral
One-point pH
calibration
pH 6.86 standard solution
Precision measurement
in broad range
Three-point
pH
calibration
pH 6.86 standard solution, pH
4.01 standard solution, and pH
9.18 standard solution
(d) If any of the following operations were performed, carry out a two-point or a three-point
calibration prior to the subsequent measurement aside from a periodic calibration.
• Replacing the internal solution for the reference electrode
• Replacement of the liquid junction section
• Replacement of the glass electrode chip
• Replacement of the reference electrode
(e)
If you use this product for the first time after your purchase of it, and when you find it necessary
to calibrate it in the course of “5.2 Measurement Procedure”, then calibrate it referring to “6.1
(2) pH Calibration Procedure”.
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