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Silver Anode
After extended use, a thick layer of Silver Chloride (AgCl) builds up
on the silver anode (figure 11) reducing the sensitivity of the sensor.
The anode must be cleaned to remove this layer and restore proper
performance. The cleaning can be chemical and/or mechanical:
Mechanical cleaning: In order to sand the silver anode, simply hold the
sensor in a vertical position. Wet the 400 grit sanding disc and gently
wrap it around the sensor and twist it a few times to lightly sand the
anode (the goal is to simply sand off any build-up without scratching
or removing layers of the anode itself). Usually, 3 to 4 twists of the
sanding disc are sufficient to remove deposits.
After completing the sanding procedure, repeatedly rinse the
electrode with distilled or deionized water and wipe with lens cleaning
tissue to remove any grit left by the sanding disc. Thoroughly rinse the
entire tip of the sensor with distilled or deionized water and install a
new membrane.
Chemical cleaning: Remove the cap membrane and rinse the sensor
with deionized or distilled water. Soak the sensing section of the sensor
in a 14% ammonium hydroxide solution for 2 to 3 minutes or in a 3%
ammonia solution overnight for 8-12 hours (most household ammonia
cleaners are typically around 3%). 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 lens cleaning tissue to
remove the residual layer from the anode. Trapping residual ammonia
under the new membrane cap can quickly tarnish the electrode and/or
give false readings and should therefore be avoided.
After performing a chemical cleaning on the polarographic sensor,
lightly sand the cathode and anode following the mechanical cleaning
procedures described previously.
If this procedure is unsuccessful, as indicated by improper sensor
performance, contact YSI Technical Support or the YSI authorized
dealer where you purchased the instrument.
Galvanic Sensors – Model # 605202
YSI recommends that the Sodium Chloride (NaCl) electrolyte solution
and cap membrane be changed every 2-4 weeks during regular use.
In addition, the electrolyte solution and membrane should be changed
if (a) bubbles are visible under the membrane; (b) dried electrolyte
is visible around the membrane; and (c) if the sensor shows unstable
readings or other sensor-related symptoms.
The Galvanic dissolved oxygen sensor is continuously reducing oxygen
even when the instrument is turned off. This factor allows the sensor to
be used with no warm-up period as soon as the instrument is powered
on. However, because the sensor is “on” all the time, some solid from
the oxidation of the zinc anode will form in the electrolyte within 1-2
weeks of activation. Small amounts of the solid will generally cause
no performance problems, but excessive amounts may result in jumpy
dissolved oxygen readings. The rate of solid formation is dependent
on the type of membrane installed. The formation of solids typically
form more rapidly with 5913 (1.25 mil PE) membrane, and less rapid
with 5914 (2 mil PE) membranes.
At the time the cap membrane is changed, YSI recommends that you
rinse the anode and cathode (figure 11) with distilled or deionized
water and wipe with a lens cleaning tissue. If white deposits are evident
on the anode after cleaning, YSI recommends that you remove this
material by sanding the anode with the 400 grit wet/dry sanding disc
included in the membrane kit following the “Mechanical Cleaning”
instructions under the Polarographic Silver Anode maintenance section
of this manual. If there are deposits on the cathode, sand the cathode
with the 400 grit wet/dry sanding disc following the maintenance
instructions listed in this manual for the Polarographic Gold Cathode.
If this procedure is unsuccessful, as indicated by improper sensor
performance, contact YSI Technical Support or the YSI authorized
dealer where you purchased the instrument.
SENSOR STORAGE
SHORT TERM STORAGE
The instrument is supplied with a plastic calibration/storage cup that
screws onto the cable. The cup is used for short-term storage (less than
1 weeks). Be sure to keep a small amount of clean tap water in the cup
during storage. With a small amount of water, the cup provides a 100%
water saturated air environment which is ideal for short-term sensor
storage.
LONG TERM STORAGE
The dissolved oxygen sensor should be stored long term in a dry state
while the pH or ORP sensor should be stored in solution. When storing
for more then 30 days, place the pH or ORP sensor in the storage
