YSI 95 - Manual (Page 18)

YSI Incorporated Model 95 14
SECTION 6 SECTION 6 SECTION 6 SECTION 6 MAINTENANCE OF THE MEA SENSOR MAINTENANCE OF THE MEA SENSOR MAINTENANCE OF THE MEA SENSOR MAINTENANCE OF THE MEA SENSOR
6.1 6.1 6.1 6.1 ANODE SERVICE ANODE SERVICE ANODE SERVICE ANODE SERVICE
Warning: Under no circumstances should ammonium hydroxide be used to clean the silver
anode. Ammonium hydroxide will permanently damage the condition of the MEA surface.
The MEA oxygen sensor is, in principle, the same as the conventional Clark oxygen sensor in that
the sensor is made of a silver anode and a gold cathode, but the cathode is a microelectrode array.
Since the current of the MEA oxygen sensor is so much smaller (on average 100 times smaller) than
the current of YSI conventional oxygen sensors, consumption of the silver anode, due to the
formation of AgCl, is minimal during the lifetime of the probe. There should not be any significant
build-up of silver chloride at the surface of the anode for 3 to 4 years, therefore, the anode should
not require chemical cleaning. However, if the surface of the silver anode has become fouled, gently
wet sand it using 400 grit wet/dry sandpaper, rinse thoroughly with deionized or distilled water and
wipe with a wet paper towel until the dark layer is removed. The directions are as follows:
Anode Cleaning Procedures (See figure 6)
ü Rinse the sensor thoroughly after removing the membrane cap.
ü Use wet 400 grit sandpaper to sand away the top layer of the anode by wrapping the sandpaper
around the anode and gently rotating it until the dark layer is removed.
ü Rinse the anode thoroughly with deionized or distilled water and wipe with a wet paper towel.
ü Rinse the anode again with deionized or distilled water.
Cathode Anode
Press lightly against
sensor surface
Wet
microcloth
Buffing Tool
Figure 6
6.2 6.2 6.2 6.2 CATHODE SERVICE CATHODE SERVICE CATHODE SERVICE CATHODE SERVICE
Warning: Under no circumstances should the gold cathode surface (the MEA surface) be
sanded. Sanding will permanently damage the condition of the MEA surface.
If the MEA oxygen sensor exhibits erratic behavior, such as a current rise at a rate of 1%/hour or
very jumpy readings, it can be serviced by buffing. You can use a few light twists against the
surface with the wet microcloth mounted on the buffing tool provided in the 9503 reconditioning
kit.