User Manual

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Table-2
Calibration Icons
pH Standard Calibration Solution Series
USA Series
NIST Series
3-point
calibration
4.00 pH
4.01 pH
7.00 pH
6.86 pH
10.01pH
9.18 pH
4.2.2 pH Calibration Modes
The instrument has 1 to 3 points auto calibration mode. The 1
st
point must be 7.00 pH (or 6.86 if using NIST). Then
choose other calibration solutions to conduct 2
nd
and 3
rd
points (see Table-3 for details). In the process of calibration,
the meter will display the electrode’s slope in acid and alkaline ranges.
Table-3 3-point Calibration Mode
USA
NIS
Calibration
icon
When to adopt
1-Point
Calibration
7.00 pH
6.86 pH
accuracy≤ ±0.1 pH
2-Point
Calibration
7.00 pH and
4.00/1.68 pH
6.86 pH and
4.01/1.68 pH
Measuring range: 0 to 7.00
pH
7.00 pH and 10.01
pH
6.86 pH and 9.18
pH
Measuring range: >7.00 pH
3-Point
Calibration
7.00pH, 4.00/
1.68 pH and 10.01
pH
6.86pH, 4.01/
1.68pH, 9.18 pH
Wide measuring range
4.2.3 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 measurements (≤ ±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. In the following cases, the meter must be re-calibrated:
a) The electrode hasn’t been used for a long time or the electrode is brand new.
b) After measuring strong acid (pH<2) or strong base (pH>12) solutions.
c) After measuring fluoride-containing solution and strong organic solution
d) There is a big difference between the temperature of the test sample and the temperature of the buffer
solution that is used in the last calibration.