Horiba Scientific LAQUA F-73A-S Instruction Manual page 105

(6) Repeatability
The repeatability shows the difference between maximum and minimum of the
indication given by three times of measurements using the standard solution of pH9
(see the values (3), (4), and (5) above).
OK (0)
OK (1)
OK (2)
NG
(7) Linearity
Regulation (Within ±0.03 pH)
This is equivalent to "0" and "I" in JIS.
The difference between pH9 theoretical value, which was obtained from measurement
values of pH7 and pH4, and the average of 3 pH9 measurements, is indicated.
● For accurate measurement
The regulation equivalent to "0" in JIS is quite strict, accordingly it requires strict
measurement condition to meet this regulation.
To insure accuracy in the measurement:
・ Use Type 1 for the pH standard solution.
・ Keep the temperature within ±0.2C by a temperature controlled bath.
・ Set the temperature in the temperature controlled bath to room temperature (25C) or
equivalent.
・ Perform light stirring using the electrode stand and a stirrer.
・ Press HOLD after the measured values completely stabilizes.
HINT!
Typical time interval for the measurement values to become stabilized is 3 minutes to 10
minutes while the electrode is immersed into the standard solution.
● When electrodes are defective
When the above measurement does not solve the defective conditions, perform the
followings.
・ Clean the electrode.
・ Confirm the right standard solution is used.
・ Check if the electrode is deteriorated, and replace it to new one if necessary.
Within ±0.005 pH
Within ±0.02 pH
Within ±0.05 pH
Over ±0.05 pH
Equivalent to 0 in JIS
Equivalent to I in JIS
Equivalent to II in JIS
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