YSI Professional Plus - Manual (Page 36)

62 63
cap. If the cathode remains tarnished, contact YSI technical Support or the
Authorized dealer where you purchased the instrument.
Silver Anode
After extended use, a thick layer of Silver Chloride (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 with
deionized or distilled water. Soak the sensing anode 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 wet paper towel to remove the residual layer from the anode. You
can smell the tip of the sensor to help ensure all the ammonia has been rinsed off.
trapping residual ammonia under the new membrane cap can quickly tarnish
the electrode and/or give false readings.
Chemical cleaning should be performed as infrequently as possible.
First attempt a membrane change and recalibrate. If a new
membrane does not resolve the problem, then proceed with cleaning.
Mechanical cleaning: In order to sand the silver anode along the shaft of the
sensor, simply hold the sensor in a vertical position. Wet the sanding disk with
a small amount of clean water then gently wrap it around the sensor shaft 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 disk are sufficient to remove deposits. However, in
extreme cases, more sanding may be required to regenerate the original silver
surface.
After completing the sanding procedure, repeatedly rinse the electrode with
clean water and wipe with lens cleaning tissue to remove any grit left by the
sanding disk. thoroughly rinse the entire tip of the sensor with distilled or
deionized water and install a new membrane.
IMPORTANT: Be sure to: (1) Use only the fine sanding disks
provided and (2) Sand as mentioned in the above procedures.
Not adhering to either of these instructions can damage the
electrodes. If this procedure is unsuccessful, as indicated by
improper electrode performance, contact YSI Technical Support
or the Authorized dealer where you purchased the instrument.
u
u
Galvanic Sensors – Model # 605202
We recommend that the Sodium Chloride (NaCl) solution and the membrane
cap be changed at least once every 60 days during regular use. In addition, the
NaCl solution and membrane should be changed if (a) bubbles are visible under
the membrane; (b) significant deposits of dried electrolyte are 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 display of the instrument is not active. this factor allows the sensor
to be used with no warm-up period as soon as the instrument is powered on
(instant on Do). 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 based on membrane type typically form more rapidly with
the 5912 (1 mil teflon), less rapid with 5913 (1.25 mil PE), and least rapid with
5914 (2 mil PE).
The Galvanic DO sensor solution will appear milky white
after use but will NOT affect the accuracy of the sensor unless
there is excessive build up. The color change is acceptable
and normal as long as DO readings remain stable.
At the time the membrane cap is changed, YSI recommends that you rinse the
anode (silver shaft of the sensor) with purified water and wipe with a clean paper
towel. If white deposits are evident on the anode after cleaning, YSI recommends
that you remove this material by sanding the anode with the sandpaper disk
enclosed in your membrane kit. Follow the “Mechanical Cleaning” instructions
under the Polarographic Silver Anode section.
IMPORTANT: Be sure to: (1) Use only the fine sanding disks
provided and (2) Sand as mentioned in the above procedures. Not
adhering to either of these instructions can damage the electrodes.
WARNING: DO NOT PERFORM THE POLAROGRAPHIC
CHEMICAL CLEANING ON A GALVANIC SENSOR. If
this procedure is unsuccessful, as indicated by improper
electrode performance, contact YSI Technical Support or the
Authorized dealer where you purchased the instrument.
i
i