The following maintenance information applies to the conventional electrode type of conductivity cell. The area of the cell that is sensitive to fouling are the electrode surfaces, these must fully “wet” to ensure accurate measurements are made.Moulded cells are often used in applications where a high level of contamination may be expected. This can include contaminates which do not contribute directly to the measured conductivity, e.g. organics, rust and suspended solids, but may form deposits on the electrode surface. In general these may be cleaned with the bristle brush provided and a weak detergent solution mixed with scouring powder.
Problems may occur in hard water areas where the gradual formation of scale will reduce the active area of the electrodes. Simple brush cleaning alone will not remove a hard deposit from the electrode surface. If scaling is suspected the cell should be removed from the system and treated with a 10% solution of hydrochloric or formic acid.The presence of bubbles will indicate that the scale is being dissolved. Cleaning is completed when the bubbles cease and usually takes 2-3 minutes. The cell must be thoroughly rinsed to remove all traces of acid before it is replaced in the system.
Note: Follow the supplier’s data sheet when handling acids and dispose of carefully acccording to your local authority regulations. Cells with stainless steel electrodes are generally used in applications where a low conductivity is combined with a low level of organic contamination and cleaning is rarely necessary. Errors in measurements can often be traced to faulty connections or incorrect setting on the instrument. However if contamination is suspected the cell should be removed from the system and cleaned if necessary.Handling of the cell electrodes will leave residues of oils and greases which will affect the wetting of the surfaces, leading to inaccurate readings. After touching the electrodes wash with a detergent solution and rinse thoroughly. After rinsing check that the surfaces maintain a complete film of water for approximately 10 seconds.