Evaluation of simple methodology for piezoelectric sensors protection

The increasing frequency of extreme storm events have implications for the operation of sewer systems, storm water, flood control monitoring and tide level variations. So, it is necessary to accurate and continuous monitor water level in several environments. Moreover, those sensors must be ready to send data during extreme events. A very common water level sensor is the piezoelectric sensor. These sensors are widely used for water level monitoring. These sensors frequently work submerged in aggressive waters due to the presence of solid particles that can enter the sensor, biological fouling over the sensor surface and oxidation due to saltwater action. This work aimed to develop a simple methodology to protect the sensors for a long-time operation. Three sensors from the same manufacturer with equal specifications were used. The first sensor was used without protection, the second sensor was placed inside a flexible plastic bottle filled with water and the third sensor was placed inside a latex bag filled with water. Over 20,000 readings were recorded on a 3 m depth water column to verify reproducibility of readings with and without sensor protection. The results show that the 3 sensors had similar performance in a fixed position, with amplitudes below 1.5 cm and standard deviation with a value of 0.2 cm. Subsequently, measurements were made by varying the position of the sensors by 50 cm until reaching a depth of 300 cm. The values of the latex-protected sensor reproduced the exact values of the unprotected sensor, while the plastic bottle sensor showed greater variation, with differences of up to 10 cm from the reference sensor. This shows that simple actions costing less than € 2 can protect and extend the life of equipment worth over € 2,500 and still maintain quality measurements.