Page 8
3. Care and Cleaning of Conductivity Sensors
3.1 Care of Conductivity Sensors
The conductivity section of the sensor supplied with TPS instruments
consists of two platinum plates or 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 2). You can help to maintain the platinum-black layer by following
these simple rules:
1. NEVER touch or rub the sensor plates or 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.
3.2 Cleaning Conductivity 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-up of material on the
sensor wires.
2. Films of oil or fat 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 3 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 2.
