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4 pH Measurement
4.1 Information regarding pH Calibration
4.1.1 Standard Buffer Solution
The meter adopts 3 series of standard buffer solutions: USA, CH, and NIST. They can be selected in
parameter P1.1 (see 6.3) as showed in Table-2
Table-2
Calibration icon
pH standard buffer series
USA
CH
NIST
3-Point
calibration
1.68 and 4.00 pH
1.68 and 4.00 pH
1.68 and 4.01 pH
7.00 pH
6.86 pH
6.86 pH
10.01 pH
9.18 pH
9.18 pH
4.1.2 3-Point Calibration
The meter can adopt 1 to 3 points’ calibration. The 1
st
point must be using 7.00 pH (or 6.86 pH) buffer
solution, and then choose other buffers to do 2
nd
point and 3
rd
point. Please refer to Table-3 for details. In
the process of calibration, the slope of acidity range and alkalinity range will be displayed.
Table-3 Calibration Mode
CH
USA
NIS
Calibration
icon
When to adopt
1-Point
Calibration
6.86 pH
7.00 pH
6.86 pH
accuracy≤ ±0.1
pH
2-Point
Calibration
6.86 pH and
4.00/1.68 pH
7.00 pH and
4.00/1.68 pH
6.86 pH and
4.01/1.68 pH
0 to 7.00 pH
6.86 pH and 9.18
pH
7.00 pH and 10.01 pH 6.86 pH and 9.18 pH
7.00 to 14.00
pH
3-Point
Calibration
6.86pH, 4.00/
1.68 pH, and
9.18 pH
7.00pH, 4.00/
1.68 pH and 10.01 pH
6.86pH, 4.01/
1.68pH, 9.18 pH
0 to 14.00 pH
4.1.3 How often to calibrate
The frequency that you need to calibrate your meter depends on the tested samples, performace of
electrodes, and the requirement of the accuracy. For High-Accuracy meaustements (≤ ±0.02pH), the
meter should be calibrated before test every time; For ordinary-accuracy Measurements (≥±0.1pH), once
calibrated, the meter can be used for about a week or longer.
