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18.2 Replatinising Conductivity Sensors
There are several ways to replatinise Conductivity sensors.
1.
The simplest way is to return the sensor to the TPS factory. We can fully clean
the sensor, replatinise it and test all aspects of its performance.
2.
An automatic replatiniser is available from TPS, along with replatinising
solution. This will plate the sensors for the right amount of time at the correct
current. Ordering details are as follows…
Automatic Conductivity Sensor Replatiniser
Part No 122160
20mL Platinising Solution (suitable for approx 30 uses)
Part No 122300
3.
Conductivity sensors can be manually replatinised, according to the following
procedure…
1)
Soak the sensor in a solution of 1 part Concentrated HCl and 10 parts
distilled water for approximately 5 minutes.
2)
Rinse the sensor well in distilled water.
3)
Immerse the sensor in platinising solution at least to the vent hole in the
white plastic cover. Platinising solution is available from TPS (part no
122300). Alternatively, platinising solution can be prepared by dissolving
1g of Hydrogen Chloroplatinate (H
2
PtCl
16
) in 30mL of distilled water, and
including about 0.01g of Lead Acetate ((CH
3
COO)
2
Pb) and a drop or two
of concentrated HCl.
4)
Apply a direct current of 10mA between pins 1 and 5 of the sensor plug, as
per the diagram below. Reverse the polarity every 30 seconds. After
approximately 8 minutes (4 minutes per sensor wire), they should have an
even “soot” like appearance. Avoid excess current and this will cause
incorrect platinising.
5)
After platinising, rinse the sensor well in distilled water.
6)
If you have any doubts about any of these steps, then you should consider
returning the sensor to the factory. The cost of replatinising is quite low,
and you will be guaranteed of the best possible result.
Pin 1
Pin 5
Sensor Connector