YSI 550A - Manual (Page 13)

YSI 550A
Y S I
Environmental
Page 9
PROBE ELECTRODE MAINTENANCE
SILVER ANODE
After extended use, a thick layer of AgCl builds up on the silver anode reducing the sensitivity of the
sensor. The anode must be cleaned to remove this layer and restore proper performance. The cleaning
can be chemical or mechanical:
• Chemical cleaning: Remove the membrane cap and rinse the electrodes deionized or distilled
water. Soak the entire anode section in a 14% ammonium hydroxide solution for 2 to 3
minutes (or a 3% solution may be used and soaked overnight for 8-12 hours). Rinse heavily
in cool tap water followed by a thorough rinsing with distilled or deionized water. The anode
should then be thoroughly wiped with a wet paper towel to remove the residual layer from the
anode.
Warning: Chemical cleaning should be performed on an as-needed basis, and no more
often than once a year (or once per six months in wastewater environments). When
readings appear unstable or the instrument will not calibrate, first attempt a membrane
change and recalibrate. If a new membrane does not resolve the problem, then proceed
with the chemical cleaning.
• Mechanical cleaning: Sand off the dark layer from the silver anode with 400 grit wet/dry
sandpaper. Wrap the wet sandpaper around the anode and twist the probe. Rinse the anode
with clean water after sanding, and wipe thoroughly with a wet paper towel.
GOLD CATHODE
For correct probe operation, the gold cathode must be textured properly. It can become tarnished or
plated with silver after extended use. The gold cathode can be cleaned by using the YSI 5238 Probe
Reconditioning Kit or 400 grit wet/dry sandpaper. Never use chemicals or abrasives not recommended
or supplied by YSI.
Using the sanding paper provided in the YSI 5238 Probe Reconditioning Kit, wet sand the gold with a
twisting motion about 3 times or until all silver deposits are removed and the gold appears to have a
matte finish. If the cathode remains tarnished, return the probe for service. Wipe the gold cathode
thoroughly with a wet paper towel before putting on a new membrane cap.
REPLACEMENT OF THE DO ELECTRODES
Should replacement of the DO Electrodes be required, the user may purchase a YSI 559 Replaceable
DO Module Kit. The kit includes an instruction sheet, DO sensor module, set screw, and hex key
wrench.