Moisture measurements in construction elements and other structures using Bluetooth Low Energy

Moisture measurements in construction elements and other structures using Bluetooth Low Energy During the last decade, the data transfer from long-term monitoring of data, recorded e. g. in structures and dams, was undergoing a challenge from cable connected sensors to Wireless Sensor Networks (WSN) [2]. The sensor networks shall act as early warning systems for the set-in of initiating damage processes or if, e. g., moisture penetrates a structural element or any massive structure (embankments, dykes, dams) that allow for adverse and damaging substances penetrating structural elements. During first feasibility tests we applied commercially available multifunctional sensors like a Bluetooth Low Energy (BLE) Module for investigation of the influence of moisture in a certain volume of building material on the received signal. The investigated parameters were the so-called Received Signal Strength Indicator (RSSI) of a Bluetooth Low Energy (BLE) Signal and the transmission power emitted by an embedded BLE-Module. The BLE-Module communicates with a mobile smart receiver as a tablet or a smartphone as s. c. SmartHub. The change of the RSS-Indicator is a measure for the damping as a result of changing moisture content in a structural element while the transmission power remains constant. While the BLE-Signal transfers a moist section in any material, eg. building material, the RSS-Indicator changes. After a successful feasibility study, a ZIM-project was confirmed, which was composed within the in the German Network MI4G (Modern Industry for Germany) between the Federal Institute for Materials Research and Testing (BAM) with the small enterprise LinTech GmbH, Berlin. The report presents first results and gives an outlook on further research activities.