Hanna Instruments HI 120 - Manual (Page 20)

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The stored calibration history to used issue error and warning messages
during calibration to help ensure the highest accuracy.
As electrode aging is normally a slow process, substantial changes from
previous calibrations are likely due to a temporary problem with the electrode
or buffers. Calibrating under these conditions will result measurement errors.
ERROR MESSAGES
Error messages appear if one or all of the calibration parameters are out
of accepted windows. When these messages are displayed, calibration
cannot be confirmed.
WRONG BUFFER
This message appears when the difference between the pH reading and
the value of the selected buffer is too big. If this error message is displayed,
check if you have selected the proper calibration buffer.
WRONG BUFFER TEMPERATURE
This message appears if the temperature of the buffer is outside the
defined buffer temperature range.
WRONG & CONTAMINATED BUFFER / CHECK ELECTRODE
This message appears if the buffer used is contaminated or the electrode is
supposed to be either broken or very dirty.
WRONG & CHECK ELECTRODE / CLEAN ELECTRODE
This message appears if the electrode is supposed to be broken or very dirty.
WRONG & OLD / CLEAR CAL & OLD
This message appears as a result of an erroneous slope condition. If the
slope between current calibration point and one of the previous calibration,
that was not overriden in current calibration, exceeds slope window (80%
to 110%), this message will appear. Press CLR to clear old parameters
and continue calibration process or CAL to leave calibration.
WARNING MESSAGES
During calibration, the Calibration Check feature analyzes the electrode
calibration history and warns the user when problems have been detected. It
is possible to override the warning messages and confirm the calibration but
it is not recommended.
CLEAR CAL IF NEW ELECTRODE
This warning is displayed any time you enter calibration and calibration is not
cleared or the new calibration parameters are better than the previous ones.
You can clear calibration history by pressing CLR, or continue by pressing CAL.
ENHANCED CALIBRATION MESSAGES