Hanna Instruments HI 222 - Manual (Page 9)

9
CAL
pH
ATC
BUFFER 1
PROCEDURE
The user has a choice of 7 memorized buffers: pH 1.68, 3.00, 6.86, 7.01,
9.18, 10.01 and 12.45.
It is always recommended to perform a two-point calibration. The instrument
however allows a one-point calibration, as described on page 10.
TWO-POINT CALIBRATION
For most applications it is recommended that pH 7.01 or 6.86 buffers to be
used as the first calibration point and pH 3.00 (for acidic samples) or pH
9.18/10.01 (for alkaline samples) as the second calibration point.
Note: The pH 12.45 buffer is not for general measurement; use only if the
sample is very alkaline to avoid sodium error.
• Immerse the pH electrode and the temperature probe approximately
4 cm (1½”) into the buffer solution of your choice (pH 1.68, 3.00,
6.86, 7.01, 9.18, 10.01 or 12.45) and stir gently. The temperature
probe should be close to the pH electrode.
• Press the CAL key. “CAL” and “pH” tags will be on, and the “CLEAR
CAL if new electrode” tag will blink.
• Press the CLR key if you are using a new electrode or want to clear the
calibration history. The instrument will display the “donE” message for
a few seconds.
It is very important to clear the calibration history when a new electrode is
used because all error and warning messages that appear during calibration
depend on the calibration history.
• Press the CAL key or wait a few seconds to continue.
Note: The above behavior appears only if calibration history is not empty.
• The instrument will display the measured pH on the primary LCD, and
the most common buffer (“7.01”) on the secondary LCD, along with
“CAL”, “pH” and “BUFFER 1” tags.
• The “ ” tag will blink until the reading has stabilized.
CLEAR CAL if new electrode
pH
CAL