Hanna Instruments HI 221 - Manual (Page 10)

10
ATC
PROCEDURE
The user has a choice of 7 memorized buffers: pH 1.68, 4.01, 6.86, 7.01,
9.18, 10.01 and 12.45.
It is always recommended to perform a two-point calibration, however the
instrument also allows a one-point calibration, as described on page 11.
TWO-POINT CALIBRATION
For most applications it is recommended that pH 7.01 or 6.86 buffers be used
as the first calibration point and pH 4.01 (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, 4.01,
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 happens 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