3.3 Ion Calibration
The pHPLUS DIRECT meter is capable of up to 3-point ion calibration
(minimum 2 point) with standard solutions to ensure accuracy across the
entire range of the meter.
To exit calibration after you have first entered into ion calibration, press the
CAL
key again. No ion calibration values are stored into the meter’s
non-volatile memory. Note that ion calibration data is lost once the meter is
reset when the batteries are removed and replaced.
If one calibration point is performed an error message “
Er2
” will be displayed
after the single point calibration is completed. Recalibrate using a minimum of
2 points.
Calibration values are successfully stored if the ISE (Ion Selective Electrode)
slope is within the specified tolerance of 15-90 mV/decade, otherwise an error
message “
Er3
” is displayed.
If any of the calibration points are not within 1 decade, an error message “
Er4
”
will be shown at the end of calibration process. The ion calibration options
available include 0.1, 1.0, 10.0, 100.0 ppm. Recalibrate and ensure that all
calibration points must be at least 1 decade apart from each other.
Ensure that you use new or fresh standard solutions during calibration. Do not
reuse ion standard solutions as they may be contaminated and affect the
calibration and accuracy of measurements. Always store standard solutions in a
dry, cool environment if possible. Check that the ISE and ion standard
solutions are kept in good condition, otherwise erroneous readings may be
taken.
Before use, remove the plastic protective cap if present on the ISE (at the tip
of sensor) and read the manufacturer’s instructional manual. Briefly rinse the
electrode with clean deionized water to remove any residue.
Rinse probes before and after each calibration or sample measurement to avoid
cross-contamination. For more details please refer to Manufacturer’s care and
maintenance guide.
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