Ph Calibration - Hanna Instruments pH 21 Instruction Manual

• After measurements, turn the meter off by pressing the ON/OFF
key, disconnect the power adapter from the mains and the
electrode from the instrument.
Note: To perform correct ORP measurements, the surface of the ORP
electrode must be clean and smooth.
Note: When not in use, the tip of the electrode should be kept moist
and safe from any mechanical stress which might cause
damage to the glass/platinum junction.
TAKING TEMPERATURE MEASUREMENTS
• The meter is factory calibrated for temperature range.
Please contact the nearest Hanna Service Center for
recalibration, if needed.
• Connect the HI 7662 temperature probe (optional) to the proper
connector on the rear panel (see page 4).
• Connect the 12VDC power adapter to the instrument (see page 4)
and then to the mains.
• Press the ON/OFF key to turn the meter
on.
• Press the RANGE key to select the tem-
perature (°C) mode.
• Immerse the probe in the sample to be tested.
• Shake briefly and wait a few seconds for
the reading to stabilize, i.e. when the
hourglass symbol stops blinking. The LCD
will show the temperature (°C) value.
• After measurements, turn the meter off by pressing the ON/OFF
key, disconnect the power adapter from the mains and the probe
from the instrument.
HOLD FUNCTION
• To freeze a reading on display, from measurement mode press
and hold the HOLD key. The "HOLD" tag will light up.
• The meter returns to normal mode when the HOLD key is released.
Note: The RANGE key is not working while in HOLD mode.
8

pH CALIBRATION

For better accuracy the instruments should be calibrated frequently,
and however:
1. After electrode replacement.
2. After testing aggressive chemicals.
3. At least once a month.
4. When extreme accuracy is required.
• Turn the instrument on after connecting the pH electrode and the
temperature probe.
• Immerse the temperature probe together with the electrode into
pH 7.01 buffer solution or manually set the temperature (see the
note here below).
Note: The pH electrode should be submerged approximately 4 cm
(1½") into the solution and the temperature probe should be
located as close as possible to the electrode.
Note: If the temperature probe is not used, measure the buffer value
with a thermometer, enter the °C mode by pressing the RANGE
key and adjust the displayed value by using the arrow keys.
• Press the RANGE key to display pH readings.
• Press the CAL key to enter the calibration mode: the display
flashes "pH 7.01" and the hourglass symbol lights up.
• Wait till the hourglass symbol on the LCD turns off and the "pH"
tag stops blinking, then press CFM to confirm the first calibration
point (offset). "pH 4.01" will flash on the LCD.
• If a single point calibration at pH 7.01 is desired, press the CAL
key to exit, otherwise proceed with the second point.
• Rinse and immerse both pH electrode and temperature probe (if
used) in pH 4.01 or pH 10.01 buffer solution. The meter
automatically recognizes the buffer and displays the correct value.
9