Hanna Instruments HI 3512 - Manual (Page 29)

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It is recommended to calibrate the instrument frequently, especially if
high accuracy is required.
The ISE range should be recalibrated:
• Whenever the ISE probe or ion charge is changed.
• At least once a day.
• After testing aggressive chemicals.
• When calibration alarm time out is expired-
“CAL DUE” warning
blinks (if feature is enabled).
Follow instructions for the individual electrode.
Due to electrode conditioning time, the electrode must be kept immersed
a few seconds to stabilize. The user will be guided step by step during
calibration with easy to follow messages on the LCD. This will make the
calibration a simple and error-free procedure.
PROCEDURE
Select the proper ISE probe in SETUP menu or select the proper Ion
Charge slope (see SETUP for details, page 40).
Note: If the ISE probe has not been previously calibrated (at least one
point), the “----” will be displayed.
Pour small quantities of the buffer solutions into clean beakers. If possible,
use plastic beakers to minimize any EMC interferences.
For accurate calibration and to minimize cross-contamination, use two
beakers for each standard solution. One for rinsing the electrode and one
for calibration.
The HI 3512 permits a 5 point calibration in 6 standard solutions
(0.1, 1, 10, 100, 1000, 10000). It is advised to bracket expected ion
concentration with your standards. For fluoride electrode the 2 ppm
standard is also available.
For accurate ISE measurements it is recommended to perform a multipoint
calibration. At least a two-point calibration is required.
Remove the protective cap from the ISE electrode.
IIIIIS E S E S E S E S E CALIBRATION CALIBRATION CALIBRATION CALIBRATION CALIBRATION