11
pH CALIBRA
TION
It is recommended to calibrate the instrument frequently, especially if high accuracy is required.
The pH range should be recalibrated:
• Whenever the pH electrode is replaced.
• At least once a week.
• After testing aggressive chemicals.
• When calibration alarm time out is expired ‑
“CAL DUE”
blinks (if feature is enabled in
SETUP
).
• If
“Outside Cal Range”
message blinks during pH measurement (the measurement range is
not covered by current calibration, if feature is enabled in
SETUP
).
PROCEDURE
HI98161
instrument offers a choice of seven standard buffers (pH 1.68, 4.01, 6.86, 7.01, 9.18, 10.01
and 12.45). The meter allow the user to set up to five custom buffers. The custom buffers are the
buffer values at 25 °C.
When a custom buffer is selected during calibration, the
Custom
functional key is displayed on the
LCD. Press
Custom
key in order to enter custom buffer changing mode. Use / keys to change
the value in a ±1.00 pH window, in according with the temperature reading and then
Accept
. Press
ESC
to leave custom buffers value unchanged.
For accurate pH measurements, it is recommended to perform a calibration with buffers that bracket
the expected pH value. At least, two point calibration is recommended.
The instrument will automatically skip the buffers used during calibration and the buffers which are
in a ±0.2 pH window around one of the calibrated buffers.
• Remove protective cap and rinse the electrode with distilled or deionized water.
• Pour small quantities of selected buffers solutions into clean beakers. For accurate calibration use
two beakers for each buffer solution, the first one for rinsing the electrode and the second one
for calibration.
