Hanna Instruments HI 98150N - Manual (Page 11)

11
pppppH CALIBRATION H CALIBRATION H CALIBRATION H CALIBRATION H CALIBRATION
Hanna recommends frequent calibrations, especially if high accuracy is
required.
The pH range should be recalibrated:
• Whenever the pH electrode is replaced.
• At least once a week, but daily is recommended.
• After testing aggressive chemicals.
• After electrode is cleaned.
• When calibration alarm time out is expired - “
Cal Due” tag blinks (if
feature is enabled).
• If “ Outside Cal Range” message blinks during pH measurement
(the measurement range is not covered by current calibration).
PROCEDURE
The instrument offers a choice of 7 buffers that are automatically recognized
(1.68, 4.01, 6.86, 7.01, 9.18, 10.01 and 12.45 pH) and also allows
the user to enter two more pH values for calibration, “
Custom 1” and
“ Custom 2”. The set custom buffers are the buffer values at 25 ºC.
HI 98160 offers also 3.00 pH buffer choice for wine measurement.
When a custom buffer is selected during calibration, the “
Custom” tag
is displayed on the LCD and its value can be changed in a ±1.0 pH
window, around the set value, in accordance with current temperature.
For accurate pH measurements, it is recommended to perform a five-point
(
HI 98150 & HI 98160) calibration respectevely a three-point (HI 98140)
calibration. However, at least a two-point calibration is suggested.
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 (HI 98150 & HI 98160)
• Submerse the pH electrode and the temperature
probe approximately 3 cm (1¼”) 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.
• Press CAL. The instrument will display the
measured pH on the primary LCD and “ 7.01”
buffer on the secondary LCD, together with
“
CAL” and “Cal Point 1” tags.
3cm
(1¼”)