5.1.1 Sensor Maintenance

To ensure the vent tube remains dry, the gauge WLTS contains a permanent desiccant and hydrophobic membrane at the connection to the Vented Cable—there is no need to replace them.

Sensor maintenance consists of cleaning the outside housing, the circulation holes in the nose cone and the NPT threading. 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 sensor 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 sensor end.

In some cases simple cleaners are insufficient to properly clean the sensor. 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 sensor. 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 sensor.

High suspended solids load may block the circulation ports or clog the internal pressure cell of the sensor. The potential clogging effect of solids deposition can be minimized by placing the sensor in zones of flow. To remove solids build up, rinse the sensor 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 sensor transducer, the conductivity wires and the sensor casing. To remove fouling use a diluted (≤10%) solution of sulfuric acid. Persistent material may require soaking for several hours. Changing or Updating WLTS

If a new WLTS is attached or you have changed the settings, ensure that the power is disconnected temporarily (30 seconds) by disconnecting the Communication/Vented Cable from the sensor. This is so the MODBUS translator will re-initialize, in order to cause the new MODBUS device address or settings to be retrieved from the WLTS.