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18. Appendices
18.1 Care, Cleaning and Maintenance of Conductivity Sensors
18.1.1
Care of Conductivity sensors
The conductivity section of the sensor supplied with your
WP-84
consists of two
platinum wires 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 section 18.2). You can help to maintain the platinum-
black layer by following these simple rules:
1.
NEVER
touch or rub the sensor wires 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 sensor wires.
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.
18.1.2
Cleaning of Conductivity of Sensors.
Platinised platinum Conductivity sensors can only be cleaned by rinsing in a
suitable solvent.
DO NOT wipe the sensor wires
, as this will remove the
platinum-black layer.
1.
Rinsing in distilled water will remove most build-ups of material on the sensor
wires.
2.
Films of oils or fats on the sensor wires 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 sensor
wires, 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, as per
section 18.2.