Campbell Scientific CSIM11 pH and ORP Sensors - Manual (Page 22)

CSIM11 pH and ORP Probes
10 minutes each. After treating the electrode with these strong acids or bases,
rinse the electrode with water and soak it in pH 4 buffer for at least 1/2 hour.
Greasy and oily coatings are best removed with a detergent solution or a
solvent that will not attack the electrode’s body. Methanol and isopropyl
alcohol are good choices for solvents. A soft toothbrush can be used with the
detergent to remove stubborn coatings.
Acetone, MEK, THF, or trichloroethane will irreparably
harm the electrode.
The pores of the reference junction may become clogged and surface cleaning
may not restore proper function. The electrode should then be heated to 60 °C
in 3 molar KCl and allowed to cool in the same solution. Rinse it with distilled
water and soak in pH 4 buffer for 1/2 hour before testing. The electrolyte
should be removed and replaced with fresh electrolyte before treating as above.
Electrodes age with time and eventually become desensitized. Extended
periods of service at temperatures greater than 80 °C or exposure to deionized
water accelerate this phenomenon. As a last resort, dip the electrode in a 10
percent ammonium bifluoride solution for 10 to 20 seconds, then rinse it with
tap water and soak it in 5-6 molar HCl for 30 seconds. Rinse it with tap water
and soak it in pH 4 buffer for 1/2 hour before testing.
The platinum sensing tip of an ORP electrode should be cleaned just like a pH
electrode. The surface can also be cleaned with an abrasive as a last resort.
Gently scour the platinum with a 600 grit wet emery cloth or preferably 1-3
micron alumina polishing powder.
10. Troubleshooting
SYMPTOM: Probe pegs at 14 pH or drifts off scale high.
POSSIBLE REASON: Open circuit in either glass electrode or reference
electrode.
CHECK:
1. Visually inspect cable and connector looking for a crushed or broken cable
jacket or a brittle cable jacket due to exposure to solar radiation. Discard
electrode if damage is present.
2. Move wires at datalogger to test for intermittent connection. Tighten
connectors if necessary.
3. Visually inspect bulb for a coating. If coated, use an appropriate solvent
or a high-quality detergent with a cotton swab to wipe bulb clean. Rinse
well with distilled water; soak in 4.0 buffer for at least 10 minutes, retest.
If electrode now responds, but erratically, soak in 10 percent HCl solution
for five (5) minutes, rinse well with distilled water; soak in 4.0 buffer for
at least 10 minutes, retest.
4. Visually inspect reference junction (large white surface at front of sensor).
If coated, clean by rinsing well; retest. If electrode still reads high, place
WARNING
14