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17.2 Conductivity/TDS
17.2.1 Care, Cleaning and Maintenance of Conductivity Sensors
Care of Conductivity sensors
The conductivity section of the sensor supplied with your
90-FL
consists of two platinum plates
that are plated with a layer of “platinum-black”. This is quite a soft layer and is required for stable,
accurate measurements. In time, the platinum-black layer may wear off in some applications, at
which time the sensor will require replatinising (see detail later in this section). You can help to
maintain the platinum-black layer by following these simple rules:
1.
NEVER
touch or rub the electrode plates with your fingers, cloth etc.
2.
Avoid using the sensor in solutions that contain a high concentration of suspended solids, such
as sand or soil, which can abrade the electrode plates. Filter these types of solutions first if
possible.
3.
Avoid concentrated acids. If you must measure acids, remove the sensor immediately after
taking the measurement and rinse well with distilled water.
Conductivity sensors can be stored dry. Ensure that the sensor is stored in a covered container, to
avoid dust and dirt build-up.
Cleaning of Conductivity Sensors.
Platinised platinum Conductivity sensors can only be cleaned by rinsing in a suitable solvent.
DO NOT wipe the electrode plates
, as this will remove the platinum-black layer.
1.
Rinsing in distilled water will remove most build-ups of material on the electrode plates.
2.
Films of oils or fats on the electrode plates can usually be removed by rinsing the sensor in
methylated spirits.
3.
Stubborn contamination can be removed by soaking the sensor in a solution of 1 part
Concentrated HCl and 10 parts distilled water. The sensor should not be soaked for more than
approximately 5 minutes, otherwise the platinum-black layer may start to dissolve.
4.
If all of these methods fail, then the last resort is to physically scrub the electrode plates, which
will remove the contaminant and the layer of platinum-black. Use only a cloth or nylon
scouring pad. DO NOT USE STEEL WOOL. The sensor will then need to be cleaned in HCl,
as per step 3 and replatinised (see detail later in this section).