Hanna Instruments HI 98180 - Manual (Page 16)

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pppppH CALIBRATION H CALIBRATION H CALIBRATION H CALIBRATION H CALIBRATION
It is recommended to calibrate the instrument frequently, especially if high
accuracy is required.
The pH range should be recalibrated:
• Whenever the pH electrode is replaced.
• At least once a week.
• After testing aggressive chemicals.
• When calibration alarm time out is expired -
“CAL DUE” blinks (if feature
is enabled in SETUP).
• If “Outside Cal Range” message blinks during pH measurement (the
measurement range is not covered by current calibration, if feature is
enabled in SETUP).
PROCEDURE
All the familly instruments offers a choice of 7 memorized buffers (1.68, 4.01,
6.86, 7.01, 9.18, 10.01 and 12.45 pH).
HI 98182/3/4/5 allow the user to set
up to 5 custom buffers. The set custom buffers are the buffer values at 25 ºC.
When a custom buffer is selected during calibration, the
“Custom” functional
key is displayed on the LCD. Press Custom key in order to enter custom buffer
changing mode. Use ARROW keys to change the value in a ±1.00 pH
window, in according with the temperature reading and then Accept. Press
ESC to leave custom buffers value unchanged.
For accurate pH measurements, it is recommended to perform a calibration in
maximum allowed points. However, at least a two-point calibration is sug-
gested.
The instrument will automatically skip the buffers used during calibration and
the buffers which are in a ±0.2 pH window, around one of the calibrated buffers.
• Pour small quantities of selected buffer solutions into clean beakers. For
accurate calibration use two beakers for each buffer solution, the first one for
rinsing the electrode and the second one for calibration.
• Remove the protective cap and rinse the electrode with some of the buffer
solution to be used for the first calibration point.
FIVE-POINT CALIBRATION FIVE-POINT CALIBRATION FIVE-POINT CALIBRATION FIVE-POINT CALIBRATION FIVE-POINT CALIBRATION
• Immerse the pH electrode and the temperature
probe approximately 4 cm (1½”) into a buffer
solution of your choice (pH 1.68, 4.01, 6.86, 7.01,
9.18, 10.01, 12.45 or a custom buffer) and stir
gently. The temperature probe should be close to
the pH electrode.