ACTA IMEKO  ISSN: 2221‐870X  June 2015, Volume 4, Number 2, 85‐89    ACTA IMEKO | www.imeko.org  June 2015 | Volume 4 | Number 2 | 85  Two application examples of RFID sensor systems‐ identification and diagnosis of concrete components and  monitoring of dangerous goods transports  Matthias Bartholmai, Markus Stoppel, Sergej Petrov, Stefan Hohendorf and Thomas Goedecke  Federal Institute for Materials Research and Testing, Unter den Eichen 87, 12205 Berlin, Germany      Section: RESEARCH PAPER   Keywords: RFID Sensors Systems; Diagnosis of Concrete Components; Monitoring of Dangerous Goods  Citation: Matthias Bartholmai, Markus Stoppel, Sergej Petrov, Stefan Hohendorf and Thomas Goedecke, Two application examples of RFID sensor systems‐ identification  and  diagnosis  of  concrete  components  and  monitoring  of  dangerous  goods  transports,  Acta  IMEKO,  vol. 4,  no.  2,  article  15,  June 2015,  identifier: IMEKO‐ACTA‐04 (5)‐02 ‐15  Editor: Paolo Carbone, University of Perugia, Italy  Received October 13, 2014; In final form November 24, 2014; Published June 2015  Copyright: © 2015 IMEKO. This is an open‐access article distributed under the terms of the Creative Commons Attribution 3.0 License, which permits  unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited  Funding:  Section 2. of this paper is part of the study (FE No. 29.0322/2013/BASt) conducted on behalf of the Federal Ministry of Transport and digital  infrastructure, represented by the Federal Highway Research Institute (BASt)  Corresponding author: Matthias Bartholmai, e‐mail: matthias.bartholmai@bam.de    1. INTRODUCTION  The combination of radio-frequency identification (RFID) tags with different types of sensors offers excellent potential for applications with regard to identification, diagnosis, and monitoring. This should be demonstrated by means of two examples of actual developments carried out by the Federal Institute for Materials Research and Testing (BAM). The Identification and diagnosis of concrete components is a major task in the maintenance of critical infrastructure, for instance concrete bridges with heavy traffic volume. A feasibility study investigates the application of RFID sensor systems for this task. The second example reviews the transportation of dangerous goods. Using modern technologies enables promising possibilities to reduce accidents and to avoid non- conformity with transportation regulations. Project results demonstrate an innovative technical solution for monitoring of dangerous goods transports with RFID sensor systems. A literature and web research was carried out to determine the state of the art and state of research in the field of embedded RFID-based sensors. The vast majority of RFID manufacturers and suppliers develop and distribute components that are used in logistics or in trade. Because of the huge demand, RFID electronics are very inexpensive. RFID tags combined with passive (powered by the induced electromagnetic field) or active (battery powered) sensors are a niche product that only few manufacturers have in their portfolio. Nevertheless, in several areas of application a growing demand of RFID sensor systems is developing [1], [2], [3], [4]. 2. IDENTIFICATION AND DIAGNOSIS OF CONCRETE  COMPONENTS  Infrastructure is subject to continuous ageing. This has given life cycle management of infrastructure an important role. Therefore, an increasing demand for reliable inspection and monitoring tools is noticeable. The prediction of the service life of a new structure at the design stage or the diagnosis and the evaluation of the residual service life of existing structures is a key aspect of concrete structure management. Life cycle analysis and risk evaluation methods can be beneficially used to assess existing structures: actions on structures, inspection- ABSTRACT  The  combination  of  RFID  tags and  energy efficient  sensors  offers  promising potential  for  identification,  diagnosis,  and monitoring  applications  −  particularly  when  it  comes  to  objects,  which  require  continuous  observation  and  which  are  difficult  to  access  with  conventional tools. This paper presents two examples as an outlook for RFID sensor systems in embedded structures and in mobile  applications.  ACTA IMEKO | www.imeko.org  June 2015 | Volume 4 | Number 2 | 86  oriented design and construction, characteristics of components and structures, life cycle costs, risk analysis and the environmental performance of a structure over its lifespan are important factors which have to be considered when the remaining service life of an infrastructure building is in question. If the possibility of efficient inspections during construction, operation, and maintenance has already been considered during the design phase, one prerequisite for reliable assessment is given. Assessment of the safety of engineering works must be conducted by examining all aspects of their behaviour and all possibilities for failure which can be manifested. Analysing potential critical situations of structures in Europe is performed by identifying so-called limit states [1]. A limit state is defined as a condition beyond which a structure is no longer able to satisfy the provisions for which it was designed. However, it has to be distinguished between ultimate and serviceability limit states. Primarily, the reactive maintenance approach has been implemented in Europe to manage the road infrastructure network with respect to deterioration. This approach may be valid for well-managed structures without deficits and exposition to unchanging loads. However, this approach is unsatisfactory to structures containing structural deficits and subjected to increasing loads, modifications or widening measures for which they are not designed. Therefore, a paradigm change from reactive to proactive infrastructure management is required and non-destructive inspection methods play a key role here. A reliable prognosis of the condition and behaviour of a structure is an important basis for an effective service life management. In order to determine the most economical moment for repair measures in the lifetime of a structure, the knowledge about the deterioration process at exposed regions as well as a detailed knowledge about the current condition of the whole structure is essential [6]. Embedded Sensors are meeting the demands for gathering more information from the inside of a structure. Wired Sensors are meanwhile well established but may have disadvantages in case of a subsequent installation in existing structures. Wireless sensors which can be embedded in concrete provide an attractive alternative solution. This study summarizes the activities of a research project which dealt with the suitability of RFID sensor tags for concrete bridge structures. Figure 1 displays the concept of the overall system for identification and diagnosis of concrete bridge elements and the interaction between the main system components. RFID is the wireless non-contact use of radio-frequency electromagnetic fields to transfer data (Figure 2) for automatically identifying and tracking tags attached to objects and is well developed and known in commercial use. Upcoming   Figure 1. Concept of the overall system for  identification and diagnosis of concrete bridge elements and  interaction between the main system  components.  Figure  2.  Scheme  of  the  interaction  between  reader  coil  and  embedded  sensor in concrete. ACTA IMEKO | www.imeko.org  June 2015 | Volume 4 | Number 2 | 87  developments in sensor based tags for monitoring purposes in logistic and transport can be modified and used in civil engineering. This technology is by all means promising to be used within a monitoring system enabling a condition assessment for concrete bridge structures. The aim of the presented project, which was commissioned by the German Federal Highway Research Institute (BASt), was to investigate modular RFID sensor systems with respect to their basic suitability for the use in concrete (bridge) structures. The selected RFID tags have a sensor interface to be connected to sensors with low power consumption. The measured values of the embedded sensors can then be read wirelessly. After a literature and product research, the project focused on basic investigations, such as: • selection of suitable sensors for humidity, temperature and corrosion activity [7], [8], which are the most relevant parameters for the long term structural integrity of concrete structures; • application of the sensors to reinforced concrete structures in order to perform an accurate and reliable diagnosis; • determination of the maximum distance (cover), at which an RFID sensor tag can still be discovered and delivers correct data to gain knowledge about the possibilities and limits of structure integration; • comparison between high frequency (HF) and ultra-high frequency (UHF) radio communication for performance evaluation using structure integrated RFID tags; • investigation in laboratory and real world application to approach the application relevant scenarios step by step. For this purpose, prototypes or RFID sensor tags where developed, assembled, encapsulated (Figure 3), and embedded in concrete specimen with size of about 30×20×5 cm3 (Figure 4). Measurements in climate chambers were carried out and showed useful results. Figure 5 shows the results of humidity measurements in a climate chamber comparing the encapsulated and in concrete embedded RFID sensor tag (red) with a not embedded tag (black). Relative humidity was applied between 10 and 90 % in steps of 20 %. While the signal sequence of the not embedded tag follows immediately the applied humidity settings, the sequence of the embedded tag is delayed caused by the transport processes through the concrete. The delay increases with increasing humidity indicating slower transport characteristics, presumably due to approximating saturation. However, measurements were successfully performed with the embedded specimen, with coherent results over the full measurement range.  Range measurements were carried out to determine the maximum distance of RFID data communication through concrete. The results show that an effective range of up to 170 mm is reachable with the developed RFID UHF system in the undisturbed case. In addition, the developed RFID sensors were successfully embedded in a reinforced concrete slab with properties of a typical bridge superstructure. The laboratory experiments have confirmed the basic functional efficiency and reliability of the developed sensor system. Further investigations will be carried out on bridge components under real application conditions. The demand for embedded sensors in civil engineering is increasing. For further developments, other measuring principles as a supplement to or a combination with the developed system are being investigated. 3. MONITORING OF DANGEROUS GOODS TRANSPORTS  The project “Sensor-enabled RFID tags for safeguard of dangerous goods” with acronym SIGRID investigates and evaluates possibilities to improve safety and security of dangerous goods transports through the use of the latest RFID technology [9]. This technology can be used to greatly enhance the transparency of the supply chain and aid logistics companies Figure 3. Encapsulated RFID sensor tag with reinforcement.  Figure 4. Preparation of concrete specimen with embedded RFID sensor tag. Figure 5. Humidity measurements, comparison between embedded and not embedded RFID sensor tags.  ACTA IMEKO | www.imeko.org  June 2015 | Volume 4 | Number 2 | 88  in complying with regulations. In the context of SIGRID custom RFID sensor tags (Figure 6) were developed to monitor dangerous goods during transport and help to prevent hazards by allowing timely countermeasures. This requires the combination of communication technology and sensor functionality with low power consumption and small design. To achieve long battery-life, the use of very energy efficient sensors is mandatory. Other desirable properties of the sensors include high accuracy, long lifetime, and short response time. For gas sensors a high selectivity is also very important. Currently four types of sensors are integrated in the RFID tag, which are a combined humidity and temperature sensor, gas sensors for carbon monoxide (CO) and oxygen (O2), and a tilt sensor. Other interesting sensor options that might be tested in future include sensors for detecting the filling level and sensors for monitoring the operation of equipment that is built into the container like a stirring unit. The integrated sensors enable the system for recognizing and evaluating of different scenarios. Adequate gas sensors indicate an emission from the containments via measured concentrations. If a possible gas release from the transported substance cannot be detected because of lacking the proper sensor, the O2-sensor can indicate a leakage through decreasing oxygen values. For numerous dangerous goods a maximal transport temperature is defined to prevent any chemical reaction. Temperatures can be measured and compared periodically to substance specific values. If that value or a tolerance is exceeded an alarm or countermeasure can be activated. The tilt sensor can be triggered on heavy vibrations or tilting of the containment. In case of a dangerous good accident the available information about the type, amount, and condition of the dangerous goods can be used to accurately inform the relief forces. Unavailable or inaccurate information represents a significant problem. This often leads to a delay of the rescue operation, because relief forces must be aware of the involved substances and their condition to effectively protect themselves against them. Within the scope of the project, an RFID tag was developed, that allows connecting with different types of sensors. This RFID tag combines the advantages of semi-active (only sensors are battery supplied) and active tags (sensors and radio communication are battery supplied). On one side this tag is compatible to the ISO 18000 respectively EPC-Gen2 standards, on the other side this tag has also the ability to communicate via the widely adopted wireless LAN standard Wi-Fi. Because the tag is woken up the same way as battery-less passive tags and for that reason does not need to power-up a receiver- module, battery-lifetimes of more than half a year are possible - just as with semi active tags. After the tag is woken up, the WLAN module is activated and allows very fast data transmission, that otherwise would only be achievable with active tags. This greater transmission speed makes the tag suitable as storage device for much larger amounts of data, than the ones that are normally possible with RFID tags. The possibility to store great amounts of data in combination with a long battery lifetime makes this tag ideal for use as a data logger. Logging intervals can be configured individually for every sensor. The tag has also an open interface which allows an easy integration of different kinds of sensors. Sensor tags, data communication, and software are combined to an interactive solution, which can tackle various scenarios during dangerous goods transports. The underlying information is provided by a data base with expert knowledge, in this case the BAM dangerous goods database "GEFAHRGUT" [10]. Figure 7 displays the interaction between the main system components during transport. Figure 7. Concept of the overall system for monitoring of dangerous goods transports and Interaction between the main system components.    Figure 6. Prototype of the sensor enabled RFID tag.  ACTA IMEKO | www.imeko.org  June 2015 | Volume 4 | Number 2 | 89  The focal point of the vehicle equipment is the on-board unit (OBU), which consists of a ruggedized industry PC that is specially designed for use in a truck. The main functions of the OBU include acquisition of position data via GPS, routing, generation of transport documents, data communication via the mobile phone network, monitoring of the load with sensors and surveillance cameras as well as WLAN connectivity. It is either possible to read the sensors of the semi-active transponders or sensors that are permanently installed in the loading area. The OBU constantly monitors the measurements to ensure, that they are in the allowable range. If that is not the case, an alarm is automatically triggered. Current status messages are transmitted to the centralized database, that has also the cargo manifest stored. In case of need, the OBU should supply the relief forces with all required information via WLAN. But if the OBU gets destroyed during an accident, all information is still available through the centralized database. 4. CONCLUSIONS  Several applications require identification, diagnosis, or monitoring or a combination of them. Often, general conditions, like mobility or embedding, favour wireless solutions. The presented examples demonstrate, that radio based communication and small-sized, low-energy demanding sensor technologies offer the basis for innovative solutions in this regards. Subsequent tasks like sensor data fusion and automated analysis and evaluation processes offer additional benefits. ACKNOWLEDGEMENT  The contribution of further and former colleagues of BAM, namely Werner Daum, Alexander Pettelkau, Mahin Farahbakhsh, David Damm, and others, is gratefully acknowledged. Section 2. of this paper is part of the study (FE No. 29.0322/2013/BASt) conducted on behalf of the Federal Ministry of Transport and digital infrastructure, represented by the Federal Highway Research Institute (BASt). The responsibility for the content lies solely with the authors. REFERENCES  [1] I. Zalbide, E. D'Entremont, A. Jimenez, H. Solar, A. Beriain, R. Berenguer, “Battery-free Wireless Sensors for Industrial Applications based on UHF RFID Technology”, Proceedings of IEEE Sensors, 2014, pp. 1499-1502. [2] G. Schirripa Spagnolo, L. Cozzella, M. Caciotta, R. Colasanti, G. Ferrari, “Analogue Fingerprinting for painting authentication”, Proceedings of 20th IMEKO TC-4 International Symposium Measurement of Electrical Quantities, 2014, pp. 297-402. [3] M. Merenda, I. Farris, C. Felini, L. 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