Hanna Instruments HI 4521 - Manual (Page 54)

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is significant. If this message is displayed, check if you have selected the appropriate calibration
standard.to be tested. Allow time for the electrode to stabilize.
• 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
Theorysection for details). 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.
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where: C
SAMPLE
- the sample concentration;
C
STD
- the standard concentration;
V
SAMPLE
- the sample volume;
V
STD
- the standard volume;
and V
T
= V
SAMPLE
+ V
STD
∆
E - the difference of potential from the electrode;
S - the electrode slope, determined in a
previous calibration;
f
- the stoichiometric ratio between sample
and standard;