23
ELECT
rODE
C
ALIB
rA
TION
Pr
OCEDU
rE
10. ELECTRODE CALIBRATION PROCEDURE
It is recommended to calibrate the instrument frequently, especially if high accuracy is required.
The pH electrode should be recalibrated:
• whenever the pH electrode is replaced
• at least once a week, but daily is advised
• after testing aggressive chemicals and after the electrode is cleaned
• when high accuracy is required
• if the pH calibration expired warning is displayed during measurement
Every time the instrument is calibrated use fresh buffers and clean the electrode (see ELECTRODE
CONDITIONING & MAINTENANCE).
Procedure
A one, two or three-point calibration can be performed, using four predefined buffers 4.01, 7.01, 8.20
and 10.01 pH. For one-point calibration any of the four buffers may be used. If the 7.00 pH endpoint
is set the 7.01 pH calibration point is recommended, or else use 8.20 pH.
Note:
The HI84502 will not accept other pH buffers for calibration.
• Pour small quantities of selected buffer solutions into clean beakers. For accurate calibration use
two beakers for each buffer solution, the first one for rinsing the electrode and the second one for
calibration.
• Put a magnetic stir bar in the beaker that will be used for calibration.
• Remove the protective cap and rinse the electrode with some of the buffer solution to be used for
the first calibration point.
• Put the first beaker with calibration buffer in the beaker holder.
• Place the electrode holder on the top of the beaker and secure it by turning clockwise and press
STIR
.
• Immerse the pH and the temperature probe approximately 2 cm (0.8”) into the buffer, paying
attention not to touch the stir bar.
To enter Electrode Calibration follow the next steps:
• Press
CAL
key then
Electrode
.
• The electrode calibration screen will be displayed.
• Press
Clear
to delete the previous calibration.