Hanna Instruments HI 4211 - Manual (Page 49)

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• Wrong new slope. Please check the standard solution: this message appears if the current slope
exceeds slope window (50% to 120% of default slope for the corresponding ion charge - see ISE Theory
section for details, page 54). Recalibrate the instrument using fresh standards.
• Wrong old slope. Press to clear old calibration: this message appears as a result of
an erroneous slope condition. Press to clear old calibration and restart calibration.
• Difference between standards temperature is too high. Press to update the calibration or
clear old calibration: this message appears when the difference between two standards temperature is
greater than 5 ºC. Recalibrate the instrument while paying attention to the standards temperature.
ISE MEASUREMENTS
Make sure the instrument has been calibrated before taking ISE measurements.
When using one of the incremental methods for measurement and no or only a one-point ISE calibration was
performed, a warning message will be displayed on the LCD, notifying the user that at least a two-point ISE
calibration must be performed.
For accurate measurements, add the appropriate ISAB (Ionic Strength Adjustment Buffer) to both samples and
standards, if necessary. If ISAB is added to the calibration standards, it is important to add ISAB also to the
samples to be measured.
DIRECT MEASUREMENT
To measure the concentration of a sample using the Direct reading mode:
• Press
and then to select ISE Measure mode for the
selected channel.
• Select the Direct reading mode (see ISE Setup for details, page 33).
• Add ISAB to the sample solution.
• Submerge the Ion Selective Electrode tip and the temperature
probe approximately 4 cm (1½”) into the sample to be
tested. Allow time for the electrode to stabilize.
• The measured concentration value will be displayed on the LCD in
the selected units.
Note: If the reading is out of range, “-----” will be displayed
on the LCD.
DIRECT/AUTOHOLD MEASUREMENT
To measure the concentration of a sample using the Direct/AutoHold reading mode:
• Press
and then to select ISE Measure mode for the selected channel.
• Select the Direct/AutoHold reading mode (see ISE Setup for details, page 33).