Yokogawa DO30G Dissolved Oxygen Sensor - Manual (Page 21)

<4. Maintenance>
4-4
IM 12J5B3-01E
4.2.2 Checking of RTD in the Sensor
The resistance temperature detector (RTD) incorporated in the DO30G sensor is a Pt 1000 Ω
RTD. This Pt 1000 Ω RTD indicates a resistance value of about 1097 Ω at 25 °C. Check the RTD
by measuring the resistance value between conductors 11 (T1) and 12 (T2). If the resistance
value differs greatly from the above value, the sensor must be replaced.
4.2.3 Judgment of Lead Electrode Fault
If no failure is found in the checks in Subsections 4.2.1 and 4.2.2, the cause of the problem may
be the end of the service life of the lead electrode or a loose connection of the conductors. In
either case, the sensor must be replaced.
[Service Life of Lead Electrode]
The lead electrode mounted in the sensor body gradually erodes due to battery action. When
span adjustment becomes impossible for a sensor which has been used in succession over a
long period even if the electrolyte/membrane assembly has been replaced, it shows that the lead
electrode has reached the end of its service life. The service life of the lead electrode varies with
the temperature of the SUM or the amount of dissolved oxygen. Under general operating condi-
tions, it should be approximately three to four years.
4.3 Expendables, Spare Parts and
Maintenance Parts
This section presents the general information on spare parts that the manufacturer recommends
you to provide and on materials that are used in maintenance and service. When procuring these
parts or materials, also refer to the Customer Maintenance Parts List (CMPL) at the end of this
manual.
4.3.1 DOX8A Maintenance Parts (Expendables) Kit
The DOX8A Maintenance Parts Kit contains, as a set, spare parts for the expendables that need
to be replaced within one year after the start of use of the DO30G Dissolved Oxygen Sensor, the
materials that are used during replacement, and a reagent that is used to prepare the calibration
solution for zero adjustment.
Note: There are two different DOX8A Maintenance Parts Kit available: style A and style B.
Be sure to use a style B membrane assembly (membrane thickness: 50 μm) for a EXA
DO
dissolved oxygen metering system.
4th Edition : Apr 05,2011