25
ISE CALIBRA
TION HI98191
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 week.
• After testing aggressive chemicals.
• When calibration alarm time out is expired‑
“CAL DUE”
tags blinks (if feature is enabled).
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 tags 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 (see
SETUP
for details,
page 31).
Note: If ISE probe is not calibrated in at least one point, the “----” will be displayed.
Pour small volumetrically measured 50 mL of calibration standard solutions and transfer 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 instrument offers a choice of six memorized standard solutions: 0.1, 1, 10, 100, 1000,
10000 ppm and calibration up to five points. For fluoride electrode the 2 ppm standard is also
available.
Remove the protective cap from the ISE electrode.
FIVE POINT CALIBRATION
• Immerse the ISE electrode approximately 4 cm (1½") into the less concentrated
standard solution and stir gently.
