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pH MEASUREMENT
10. pH MEASUREMENT
The
HI84534
can be used as a pH meter for direct measurements.
Verify that the instrument has been calibrated before taking pH measurements. From titrator mode
press
Meter
. If an electrode calibration hasn’t been performed, or the number of days exceeds the
calibration time out value set, the message
“CAL DUE”
will blink on the left side of the display (see
Calibration timeout
option in Setup for details).
To take pH measurements:
• Submerge the pH electrode 2 cm (0.8’’) and the temperature probe into the sample to be tested
and stir gently. Allow time for the electrode to stabilize. When the reading becomes stable, the
symbol will disappear.
• If the pH reading is less than -2.00 pH or greater than 16.00 pH, the closest full-scale value
will be displayed blinking.
• Press the
Log
key to save the current reading. A message indicating the free log space will be
displayed for a few seconds.
If measurements are taken successively in different samples, it is recommended to rinse the electrodes thoroughly
with deionized or distilled water and then with some of the next sample to prevent cross-contamination.
The pH measurements are affected by temperature. In order to have accurate pH measurements, the
temperature effect must be compensated for. To use the Automatic Temperature Compensation (ATC) feature,
connect and submerge the
HI7662-T
temperature probe into the sample as close as possible to the electrode
and wait for a few seconds. The
“ATC”
message will be shown on the display. Automatic Temperature
Compensation will provide pH corrected values for the measured temperature. If Manual Temperature
Compensation (MTC) is desired, the temperature probe must be disconnected from the instrument.
The default temperature of 25 °C (77 °F) or the last temperature reading will be displayed, preceded
by the symbol and the
“MTC”
message.
The temperature can be adjusted with the
/
keys (from -20.0 to 120.0 °C).