Yokogawa DO30G Dissolved Oxygen Sensor - Manual (Page 19)

<4. Maintenance>
4-2
IM 12J5B3-01E
4.2 Inspection If Failure Occurs
If the electrolyte and/or lead electrode within the sensor unit deteriorates and ultimately com-
pletes its service life, anomalies, such as the failure to make a span adjustment, will occur. This
section deals especially with the inspection and service of the dissolved oxygen sensor needed if
any anomaly is found in a detected signal. If you fail to pinpoint the cause of failure to a particular
location, follow the instructions in Section 4.2.1 and subsequent sections in sequence. One or
more of the following measures are necessary to remedy the failure.
• Replacement of electrolyte/permeable-membrane assembly
• Replacement of sensor unit
4.2.1 Inspecting the Permeable-membrane Assembly (for
Damage)
Note : When the membrane is used in the float holder, the converter membrane damage detector function can be used. This function
generates an "E4" error message if the membrane is damaged.
Check the permeable-membrane assembly for possible wrinkling or damage. Also, check that
the permeable-membrane assembly locknut is not loose. If the locknut is securely tightened and
the membrane is normal (no wrinkling or damage is found), proceed to the instruction procedure
in Section 4.2.2. If the locknut is loosen or the membrane is wrinkled or damaged, replace the
electrolyte and the permeable-membrane assembly (including the O-ring seal) as well.
[Electrolyte/permeable-membrane assembly replacement procedure]
When replacing the electrolyte and permeable-membrane assembly, you must provide a syringe
and beaker that are used to replace the electrolyte and an abrasive and gauze to polish the silver
electrodes. Provide these materials along with the spare electrolyte solution and assembly used
in the replacement.
CAUTION
Precautions in Handling the Electrolyte
The potassium-hydroxide electrolyte (KOH) is a highly alkaline solution containing potassium
hydroxide as the major constituent. Exercise extreme care to protect your body from contact
with the solution and to prevent the solution from getting into your eyes. Should your skin or eyes
become exposed to the solution, immediately wash the exposed area with clean water. If the
solution gets in your eyes, consult an eye doctor after flushing them with water. The electrolyte
is a colorless corrosive and, therefore, there is the risk of its being mishandled. Never leave any
residual solution in the syringe.
(1) After having removed the dissolved oxygen sensor from the holder, clean dirt off the wet
part.
(2) Loosen the locknut and remove the permeable-membrane assembly. Also, remove the O-
ring.
4th Edition : Apr 05,2011