Monitoring of Hydraulic Structures: Long-Term Testing of Inclination Sensors

Structural health monitoring of massive hydraulic structures is becoming increasingly important in Germany due to the age structure and condition of the infrastructure necessary to ensure safe shipping. A survey within the Federal Waterways and Shipping Administration (WSV) has shown that inclination sensors are most frequently used in the monitoring systems of massive hydraulic structures. However, inclination sensors are prone to drift, which can lead to misinterpretation of measurement data, especially over long measurement periods. The potential of the inclination sensors on the one hand and their deficits on the other hand show the necessity to examine their behavior under long-term testing conditions. Eight potentially suitable inclination sensor models are tested under typical and comparable environmental conditions. Since each sensor is unique, three identical single-axis inclination sensors of each model are tested. The test rig is designed for long-term stability. So far, the 24 inclination sensors have been measuring for almost 2 years in a closed concrete block under the open sky to replicate typical environmental conditions (temperature, solar radiation, etc.). Various temperature sensors installed in the concrete block ensure compensation for temperature effects. An automatic and a manual reversal measurement are used as references because they detect and eliminate their own linear sensor drift. In addition to explaining the design of the test rig, an interim result is presented that identifies the inclination sensor models that show the lowest sensor drift and sufficient long-term stability.