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28
pH ELECTRODE CONDITIONING
& MAINTENANCE
Preparation
Remove the protective cap.
DO NOT BE ALARMED IF ANY SALT DEPOSITS ARE PRESENT. This is
normal with pH electrodes and they will disappear when rinsed with
water.
During transportation tiny air bubbles may have formed inside the glass
bulb (membrane). Shake down the electrode, as you would do with a
glass thermometer to remove the bubbles.
If the bulb and/or junction are dry, soak the electrode overnight in
HI
70300
Storage Solution.
Storage
To minimize noise and assure a quick response time, the glass bulb and
the junction should be kept moist at any time and not allowed to dry out.
This can be achieved by installing the electrode in such a way that it is
constantly in a well filled with the sample.
When not in use, pour a few drops of
HI 70300
Storage Solution or
HI
7007
pH 7.01 Buffer Solution in the protective cap and place it on the
electrode.
NEVER USE DISTILLED OR DEIONIZED WATER FOR STORING PURPOSES.
Periodic maintenance
Rinse off any salt deposits with water.
Inspect the electrode and the cable. The electrode connection cable must
be intact. There must be no points of broken insulation on the cable or
cracks on the electrode stem or bulb. If any scratches or cracks are
present, replace the electrode.
The connector must be perfectly clean and dry.
Cleaning procedure
Soak the electrode in
HI 7061
General Cleaning Solution for approxi-
mately half an hour.
For a more specific cleaning procedure, refer to the electrode’s instruction
manual.
Note:
After performing a cleaning procedure, rinse the electrode thor-
oughly with distilled water and recalibrate the controller.
• Stir the probe and tap it gently to the
bottom of the beaker to ensure that
any air bubbles trapped inside it.
For best results, do not put the probe
close to the walls of the beaker or lying
on the bottom.
• Wait for the reading to stabilize. Adjust
the SLOPE trimmer to display the same
value as the calibration solution
@25°C. For example, with
HI 7039
buffer solution, adjust the trimmer to
display “5.00”.
Note:
Once the controller has been calibrated by referring to the value
@25°C of the calibration solution, all the subsequent measure-
ments are temperature compensated to 25°C. Temperature com-
pensation to a different temperature reference point can be ob-
tained by calibrating the meter to that value. For example, the
conductivity value of
HI 7031
@20°C is 1.28 mS/cm. By adjust-
ing the trimmer to display this values, all the subsequent mea-
surements will be compensated to a temperature of 20°C.
The conductivity calibration is now complete.
