Logger maintenance consists of cleaning the outside casing and the circulation holes. The required frequency of cleaning is dependent on several aspects of the monitored water quality. In freshwater with good to excellent water quality, the cleaning requirements will be very minimal; amounting to a seasonal or even annual maintenance inspection.
In most cases cleaning can be accomplished by rinsing the logger and using mild, non-residual, non-abrasive household cleaners with a very soft-plastic, bristled, pipe-cleaner type brush. Do not insert any object through the circulation holes at the sensor end of the logger.
In some cases simple cleaners are insufficient to properly clean the logger. Several commonly occurring water conditions require specific maintenance methods. These include hard water, high suspended solids loading, biological or chemical fouling and salt or brackish water conditions.
Hard water monitoring can result in the precipitation of calcium and magnesium deposits on the pressure transducer as well as other components of the logger. These deposits can be safely dissolved using a diluted solution (typically ≤ 10% strength) of acetic or phosphoric acid. Commercially available products for dissolving hard water scaling are also available and can be used if designed for household use. Some industrial strength hard water scaling removers are much higher strength and are not recommended for cleaning the logger.
High suspended solids load may block the circulation ports or clog the internal pressure cell of the logger. The potential clogging effect of solids deposition can be minimized by placing the logger in zones of flow. To remove solids build up, rinse the logger under a low flow of tap water until particles have been washed away.
Bacteriological or chemical fouling can be an important consideration in many ground and surface water monitoring projects. Sessile bacteria will often utilize installed instrumentation as an attachment substrate. Chemical deposit can be the result of electrical charge differential between the instrumentation of the monitored liquid or the result of biological or algal activity. Both forms of fouling can result in difficult to remove deposits on the logger transducer, the conductivity wires and the logger casing. To remove fouling use a diluted (≤10%) solution of sulfuric acid. Persistent material may require soaking for several hours.
Replacing the o-ring should be done on a regular basis. The o-ring ensures a tight seal at the Vented Cable connection, which is important for keeping moisture out. Replacement O-rings are available in sets of ten from Solinst.
Figure 9-1 O-Ring at the Vented Cable Connection
Proper storage when not in use is important. The logger should be stored with the protective cap threaded onto the Vented Cable connector. The hard case that the logger was received in, should also be used to protect the logger during storage.
Figure 9-2 Logger with Storage Cap and Protective Case