YSI 95 - Manual (Page 19)

Maintenance of the MEA Sensor Section 6
YSI Incorporated Model 95 15
Note: The MEA sensor does not require buffing (cleaning) every time the membrane cap is
changed. Under normal operating conditions, the MEA sensor should be buffed no more than two
times per year.
Cathode Cleaning Procedures
ü Remove the membrane cap and rinse the sensor thoroughly with deionized or distilled water.
ü Place the microcloth on the buffing tool (self-adhesive). Wet the microcloth thoroughly with
deionized or distilled water.
ü Twist the buffing tool back and forth three times in opposite directions while lightly pressing
the buffing tool against the sensor surface (see figure 6).
ü Rinse the sensor surface well with deionized or distilled water after buffing.
6.3 6.3 6.3 6.3 DISSOLVED OXYGEN PROBE PRECAUTIONS DISSOLVED OXYGEN PROBE PRECAUTIONS DISSOLVED OXYGEN PROBE PRECAUTIONS DISSOLVED OXYGEN PROBE PRECAUTIONS
Membrane life depends on usage. If the probe is properly maintained, one membrane cap should
last two to four weeks depending on how often the probe is used and the type of samples measured.
It is recommended that membrane caps not be re-used.
1. To keep the electrolyte from drying out, store the probe in a moist environment, such as the
calibration chamber with the wet sponge inside.
2. Erratic readings are a result of loose, wrinkled, damaged, or fouled membranes, or from large
(more than 1/4 of the circumference of the probe) bubbles in the electrolyte reservoir. If erratic
readings or evidence of membrane damage occurs, you should replace the membrane cap and
the KCl solution. The average replacement interval is two to four weeks.
3. If the membrane is coated with oxygen consuming (e.g. bacteria) or oxygen evolving organisms
(e.g. algae), erroneous readings may occur.
4. Chlorine, sulfur dioxide, nitric oxide, and nitrous oxide can affect readings by behaving like
oxygen at the probe. If you suspect erroneous readings, it may be necessary to determine if
these gases are the cause.
5. Avoid any environment that contains substances that may attack the probe materials. Some of
these substances are concentrated acids, caustics, and strong solvents. The probe materials that
come in contact with the sample include FEP Teflon, stainless steel, epoxy, polyetherimide and
the polyurethane cable covering.
6. Do not allow the probe to strike hard objects. The membrane or sensor inside may be damaged.
6.4 6.4 6.4 6.4 PROBE STORAGE PROBE STORAGE PROBE STORAGE PROBE STORAGE
For long term storage (4 weeks), remove the membrane cap, thoroughly rinse the MEA sensor with
deionized or distilled water and install a new membrane cap filled with MEA probe solution. Store
the sensor in a humid environment such as the calibration chamber with the wet sponge inside. Do
NOT store the probe dry.