Using RFID in Construction Applications
RFID is constantly evolving for use in new applications and different environments, largely due to the development of transponders. Such developments include the decreasing in size, yet increasing in functionality of transponders; increased read ranges and speed; and larger memory capabilities. RFID can even perform reliably in environments such as in liquid, on metal and in concrete. This requires not only robust design, but the entire RFID system must overcome key design challenges for the transmitting of RF waves.
Metal and Liquid Environments
Using UHF RFID transponders in set applications, such as on metal or in liquid, can result in significant challenges. When attached to metal, the RF waves can be reflected resulting in interference with the system performance, decreased read ranges and poor transponder responses. Alternatively, liquid has the effect of absorbing the RF waves, which can prevent the RF waves from reaching the transponder, therefore having a negative effect on the read range. There is the possibility that in extreme conditions, liquid can prevent the transponder from being read at all.
Prefabricated concrete presents the combination of metal and liquid environments, as it contains an embedded metal rebar whilst having high moisture content where the environment is saturated. Another problem is presented in the salt used for de-icing – it can seep through cracks in the concrete causing the rebar to corrode, therefore influencing the ability to read the transponders.
Within precast concrete sections, integration of RFID transponders is simple, as during the pouring process a HARTING tag can be fixed to the rebar within the concrete section - the tags are rugged in design therefore they are not susceptible to damage during the manufacturing process.
The development of smart passive transponders continues to present new opportunities for RFID to enhance current methods and procedures. For example, transponders capable of measuring the temperature change within the concrete during the curing process. These could be built into precast concrete sections, wiring the transponders to the metal rebar. This would enable an engineer to monitor the stability of the concrete – as the rebar corrodes, therefore weakening the structure of the concrete, this would create an increased resistance between the rebar and transponder, which the smart transponder would display when read.
It is possible for smart transponders to be used in the detection of fracturing and cracking in concrete sections. This is achieved by the use of passive transponders that have the capability to detect a wire disconnection as part of the installation.
Manufacturing a Solution
The reliability of standard tags in liquid and metal environments has been a topic of importance within the RFID industry. Developments are continuing to resolve the issues mentioned within this blog, to ensure that the transponder, as well as its associated mounting accessories, enables the system to read transponders despite the effects of liquids and metals on RF waves. There is an increased issue when both the transponder and the antenna are located within the same liquid/metal environment.
Manufacturers of RFID solutions design transponders and mounting solutions to avoid the issues of reflecting RF waves and the decreasing of transponder performance in high moisture or liquid environments.
HARTING has produced not only a range of tags that perform on-metal, but also a range of transponders that are designed specifically for embedding in concrete. These can be used for the identification of prefabricated concrete components, cables and piping buried in the ground, and the localisation of storage areas within warehousing.
HARTING RFID Transponders are available to buy now from RS Components.
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January 27, 2012 14:18