Page 27
11. Appendices
11.1 Care, Cleaning and Maintenance of Conductivity Sensors
11.1.1
Care of Conductivity Sensors
The conductivity section of the electrode supplied with your
901-C
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
electrode will require replatinising (see section 11.2). You can help to maintain
the platinum-black layer by following these simple rules:
1.
NEVER
touch or rub the electrode wires with your fingers, cloth etc.
2.
Avoid using the electrode in solutions that contain a high concentration of
suspended solids, such as sand or soil, which can abrade the electrode wires.
Filter these types of solutions first, if possible.
3.
Avoid concentrated acids. If you must measure acids, remove the electrode
immediately after taking the measurement and rinse well with distilled
water.
Conductivity electrodes can be stored dry. Ensure that the electrode is stored in a
covered container, to avoid dust and dirt build-up.
11.1.2
Cleaning of Conductivity Sensors
Platinised platinum Conductivity electrodes 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 wires.
2.
Films of oils or fats on the electrode wires can usually be removed by
rinsing the electrode in methylated spirits.
3.
Stubborn contamination can be removed by soaking the electrode in a
solution of 10 parts distilled water TO 1 part Concentrated HCl. The
electrode 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 electrode will then need to be cleaned in HCl, as per
step 3 and replatinised, as per section 11.2.