Hanna Instruments HI 21 Series - Manual (Page 21)

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PH BUFFER SELECTION (HI 21523 ONLY)
A one point pH calibration at a value different from standard
buffer is possible by directly entering the desired calibration
value.
• Pour a small quantity of the calibra-
tion solution in a beaker and then
press CAL to enter the calibration
mode.
• After the correct password is entered,
the control action stops and the pri-
mary LCD will display the pH value
using the current offset and slope,
with the "CAL" and "
BUF
1 " indicators
lit and the probe indicator " " blink-
ing.
• Press SETUP and the pH value on
the secondary LCD will start blink-
ing.
• By the , and keys select the pH calibration value
of the buffer.
• Immerse the electrodes in the buffer solution.
• When the reading is stable press CFM to confirm the cali-
bration.
Note During calibration with pH buffer solutions different from stan-
dard, the stability check function is not active. No “CAL” or
"
BUF
1 " indicators will blink, hence wait for the reading to stabi-
lize after having immersed the electrode in the calibration
solution.
Note If the wrong password is entered the system reverts back and
restarts displaying the pH value.
Note Calibration can be aborted by pressing SETUP before CFM .
Calibration is restarted with no changes to calibration data.
CALIBRATION WITH MANUAL TEMPERATURE COMPENSATION
• Enter the calibration procedure and press LCD to display
the temperature on the secondary LCD.
• Unplug any temperature probe that may
be attached to the meter. The "°C" sym-
bol will flash.
• Note the temperature of the buffer solutions with a
ChecktempC or another accurate thermometer with a reso-
lution of 0.1°C.
• Use or to manually adjust the display reading to the
value of the reference thermometer (e.g. 20°C).
• Follow the calibration procedure above.
Note To toggle between the pH buffer and
the temperature press LCD.
When a one-point calibration is carried out only the pH off-
set is computed and stored, while the pH slope is fixed
according to the theoretical values.
With a two-point calibration, offset and slope are computed
to fit the two calibration points. With a three-point calibra-
tion the offset and first slope values refers to pH 4.01 and
7.01 buffers, while the second slope refers to pH 7.01 and
10.01 buffers.
Note If the process meter has never been cali-
brated or an EEPROM reset has occurred,
the meter continues to perform measure-
ment. However, the user is informed of a pH calibration
requirement by a blinking “CAL” (see “Start-up” section).
The device must be calibrated within the temperature range
of 0-95°C. Outside this range, the buffer pH values are not
reliable.