Hanna Instruments HI 4521 - Manual (Page 43)

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pH CALIBRATION pH CALIBRATION pH CALIBRATION pH CALIBRATION 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 LCD, in the Reminder messages area.
PREPARATION
Pour small quantities of the buffer solutions into clean beakers. If possible, use plastic beakers to minimize
any EMC interferences.
For accurate calibration and to minimize cross-contamination, use two beakers for each buffer solution. One
for rinsing the electrode and one for calibration.
If you are measuring in the acidic range, use pH 7.01 or 6.86 as first buffer and pH 4.01/3.00 or 1.68 as
second buffer. If you are measuring in the alkaline range, use pH 7.01 or 6.86 as first buffer and pH 10.01/
9.18 or 12.45 as second buffer.
For extended range measurements (acidic and alkaline), perform a five-point calibration by selecting five of
the available buffers.
CALIBRATION PROCEDURE
Calibration has a choice of 8 memorized buffers: pH 1.68, 3.00, 4.01, 6.86, 7.01, 9.18, 10.01, 12.45 and
up to 5 custom buffers.
For accurate measurements it is recommended to perform a five-point calibration. However, at least a two-point
calibration is suggested.
pH Calibration screen description
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Units
The user can select the desired measurement unit. The available options are:
µ S, mS or AutoRanging.
• Use or to highlight the Units option.
• Press to confirm your selection.
• Use or to select µ S, mS or AutoRanging.
• Press to confirm your selection or press to
cancel operation.
Clear Calibration
Accessing this option, the existent conductivity calibration can be cleared. If the calibration is cleared, another
calibration has to be performed.
To clear calibration:
• Use or to highlight the Clear Calibration option.
• Press to clear calibration. A pop-up menu will be displayed asking for confirmation.
• Press to confirm or press to escape without saving and return to the Calibration options.
Probe Type
This option allows the user to obtain some information about the connected conductivity probe: name, default cell
constant, range and rings number.