12
FOUR, THREE OR TWO-POINT CALIBRATION
• Proceed as described in “FIVE-POINT CALIBRATION” section.
• Press
CAL
after the fourth, third or second calibration point was
confirmed. The instrument will memorize the calibration data and
return to measurement mode.
ONE-POINT CALIBRATION
Two SETUP selectable options are available: “
Pnt
” and “
OFFS
”.
If the “
Pnt
” option is selected, the new calibration point overrides an
existing one. The adjacent slopes will be reevaluated.
If the “
OFFS
” option is selected, an electrode offset correction is
performed. The adjacent slopes will remain unchanged.
• Proceed as described in “FOUR, THREE or TWO-POINT CALIBRATION”
section.
• Press
CAL
after the first calibration point was confirmed. The
instrument will memorize the one-point calibration data and return
to measurement mode.
• The “ ” tag will blink on the LCD until the reading is stable.
• When the reading is stable and close to the selected
buffer, the “
READY
” tag will be displayed and the
“
CFM
” tag will blink.
• Press
CFM
to confirm calibration.
• The calibrated value is then displayed on the
primary LCD and the fifth expected value on the
secondary LCD.
• After the fourth calibration point is confirmed, submerse the pH
electrode and the temperature probe approximately 3 cm (1¼”)
into the next buffer solution and stir gently. The temperature
probe should be close to the pH electrode.
• If necessary, press the
ARROW
keys to select a different buffer value.
• The “ ” tag will blink on the LCD until the reading is stable.
• When the reading is stable and close to the selected
buffer, the “
READY
” tag will be displayed and the
“
CFM
” tag will blink.
• Press
CFM
to confirm the fifth calibration point.
• The instrument stores the calibration value of the
fifth point and returns to normal measurement mode.
37
For refillable electrodes:
If the filling solution (electrolyte) is more than 2½ cm (1”) below the fill
hole, add
HI 7082
or
HI 8082
3.5M KCl Electrolyte Solution for double
junction or
HI 7071
or
HI 8071
3.5M KCl+AgCl Electrolyte Solution for
single junction electrodes.
For faster response, unscrew the fill hole screw during measurements.
For AMPHEL
®
electrodes:
If the electrode does not respond to pH changes, the battery is run down
and the electrode should be replaced.
MEASUREMENT
Rinse the electrode tip with distilled water. Submerse the tip (3 cm /1¼”)
in the sample and stir gently for a few seconds.
For a faster response and to avoid cross-contamination of the samples,
rinse the electrode tip with a few drops of the solution to be tested, before
taking measurements.
STORAGE PROCEDURE
To minimize clogging and assure a quick response time, the glass bulb
and the junction should be kept moist and not allowed to dry out.
Replace the solution in the protective cap with a few drops of
HI 70300
or
HI 80300
Storage Solution or, in its absence, Filling Solution
(
HI 7071
or
HI 8071
for single junction and
HI 7082
or
HI 8082
for
double junction electrodes). Follow the Preparation Procedure before
taking measurements.
Note:
NEVER STORE THE ELECTRODE IN DISTILLED OR DEIONIZED WATER.
PERIODIC MAINTENANCE
Inspect the electrode and the cable. The cable used for connection to the
instrument must be intact and there must be no points of broken
insulation on the cable or cracks on the electrode stem or bulb. Connectors
must be perfectly clean and dry. If any scratches or cracks are present,
replace the electrode. Rinse off any salt deposits with water.
For refillable electrodes:
Refill the reference chamber with fresh electrolyte (
HI 7071
or
HI 8071
for
single junction and
HI 7082
or
HI 8082
for double junction electrodes).
Allow the electrode to stand upright for 1 hour.
Follow the Storage Procedure above.
