Hanna Instruments HI 9812 Instruction Manual page 10

p p p p p H CALIBRATION H CALIBRATION H CALIBRATION H CALIBRATION
H CALIBRATION
For greatest accuracy, frequent calibration of the instrument is recom-
mended. The instrument should be recalibrated for pH:
a) Whenever the electrode is replaced.
b) At least once a month.
c) After testing aggressive chemicals.
d) Where extreme accuracy is required.
PREPARATION
Pour small quantities of pH 7.01 (HI 7007
or HI 8007) or pH 4.01 (HI 7004 or
HI 8004) or pH 10.01 (HI 7010 or HI
8010) solution into a clean beaker.
To obtain accurate readings, use pH 7.01 (HI 7007 or HI 8007) if
you are going to measure neutral or close to neutral samples, pH 4.01
(HI 7004 or HI 8004) if you are going to measure acidic samples
or pH 10.01 (HI 7010 or HI 8010) for alkaline measurements.
If you need to calibrate HI 9812 and HI 9813 to NBS standards, use
pH 6.86 (HI 7006 or HI 8006) instead of pH 7.01 and pH 9.18
(HI 7009 or HI 8009) instead of pH 10.01.
PROCEDURE
• Switch the meter on after connecting the electrode and press pH to
display pH measurement.
• Remove the protective cap from the electrode, rinse
and immerse it in the buffer and stir gently. Wait a
couple of minutes for the reading to stabilize.
• If the buffer solution is not at ambient temperature,
take its temperature with a ChecktempC (or an accu-
rate thermometer), e.g. 10.0°C.
Note: the electrode should be submerged approximately 4 cm (1½") into the
solution. The ChecktempC should be located close to the electrode.
• Adjust the pH calibration knob until the LCD
shows the pH value at the above temperature
(see the pH versus temperature chart on page
12).
• The pH calibration is now complete.
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