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Remove the screen by unscrewing two retaining screws at the bottom of the probe,
situated on the flange. Pull the tube out and wash it and also clean the glass tube.
Reinsert the screen and do up the two retaining screws.
Conductivity Sensor Maintenance
To maintain the performance and accuracy of the conductivity / salinity sensor, the
electrodes need to be periodically cleaned and if the platinum black coating is damaged,
the electrodes will need to be re-platinised.
Inspect the sensor on a regular basis. If there is any evidence of a build up of
contamination on the electrodes, then the sensor should be removed and cleaned using
the platiniser unit as described below. If the platinum black coating is damaged, the
electrodes should be cleaned and then re-platinised. To perform these operations,
proceed as follows:
1.
To remove the sensor, lift the sensor guard and rotate the bottom section of the
probe to expose the sensors. Ensure that the probe and sensors are completely
dry. Use a cotton bud to dry the area between the sensors. Pull the conductivity
sensor down out of the probe by hand. Do not twist the sensor. Ensure that the
vacant sensor socket is kept completely dry.
2.
To clean the electrodes, plug the sensor into the platiniser unit. Connect the unit
to a 6V power supply (such as a lantern battery). Fill the platiniser with 0.1M HCl
and switch on the platiniser for 5 minutes. Switch off the platiniser and rinse
with distilled water. Now inspect the electrodes. If the platinum black coating is
intact, replace the sensor in the probe assembly as described in step 5 below. If
the electrodes need to be re-platinised, proceed as follows.
3.
To strip the old platinum black coating from the electrodes, plug the sensor into
the platiniser unit fill with 5M HCl. Connect the unit to a 6V power supply and
switch the unit on. The old platinum black will be stripped off the electrodes.
Once completed, switch the platiniser off and rinse with distilled water.
4.
To replace the electrode coating, plug the sensor into the platiniser unit and
connect to a 6V power supply. To make the platinising solution, mix 3g of
chloroplatinic acid with 0.3g of lead acetate and top up to 100ml with distilled
water. Fill the platiniser with platinising solution and switch the unit on for 10
minutes. The electrodes will be plated with a sooty black coating. When
complete, rinse the unit and electrodes with distilled water then fill the unit
with 0.1M HCl and switch on for 2 minutes to remove any occluded platinum
black solution remaining on the electrodes. Rinse the sensor and platiniser with
distilled water and install the sensor in the probe assembly.
5.
Before installing the conductivity sensor into the probe assembly, make sure
that both the sensor and probe assembly are dry. Apply a smear of vacuum