With the skyrocketing cost of wiring and the growing demand for distributed and remote sensing, data acquisition and control, the role of wireless communications only gets bigger. Sensor manufacturers are integrating RF systems in the same enclosure as their sensing devices. Datalogger vendors are beginning to turn to wireless communications to enhance their products. And wireless networks are taking their place right next to traditional hardwired configurations. The industry is moving toward the implementation of networks of wireless sensors that can operate in demanding environments and provide clear advantages in cost, size, power, flexibility, and distributed intelligence.
The benefits of RF
Wireless communication is a viable and cost-effective method of transmitting data over long distances, through electrically noisy environments, and from hostile locations. The reliability and flexibility of advanced wireless technology warrants serious consideration for many industrial applications. By becoming acquainted with the capabilities of this useful tool, OEMs can take advantage of the technology in the more challenging sensor environments and reap cost and performance benefits that rival those of hardwired systems. Advantages:
* Speeds installation and reduces cost.
* Operates in RF-dense environments.
* Tolerates extended temperatures (-40 to +80°C).
* Small form factor fits inside space-constrained enclosures.
* Less invasive than cable installation.
Description of integration and use
The central component of a typical RF data acquisition (DA) system is the RF transceiver. The remote-station modem is connected to an RS232 port of a data- logger, DA front-end, or other DA device. This modem then transmits data to a base station modem connected in most cases to an RS232 port on a computer. AeroComm's ConnexRF modems are addressable and can be configured to communicate in various topologies to suit application requirements. The range of the transceivers is influenced by such factors as signal path, frequency band, multipath propagation (fading), transmission line loss, and antenna height and gain.
Developing a wireless DA system that uses more than one modem pair requires some form of system integration. AeroComm's familiarity with RF DA ensures proper selection of equipment, installation, software interfacing, and adherence to FCC regulations.
A key element of RF DA system design is a site survey, which reveals the strengths and weaknesses of a proposed location and determines appropriate modem locations, antenna systems, and potential error rates. At a minimum, a site survey should include a test of signal path propagation at the proposed location and frequency of operation, a frequency search for existing users, and a review of data throughput requirements. AeroComm's Design Kit can significantly simplify this effort for the OEM.
The cost-effectiveness of an RF DA link can be determined by comparing its cost against that of other approaches, such as installing hardwired DA systems, sending personnel periodically to collect data from remote locations, using fibre-optic links in high-EMI areas, or leasing telephone lines for long distances. Wireless DA links prove to be an excellent cost alternative to hardwired systems, as projected costs of cable, conduit, and trenching greatly exceed the cost of an RF modem pair.
Typical applications
RF DA systems are particularly effective in applications requiring acquisition of data from locations some distance away or from environments known to have high levels of EMI. For example, power generating plants and distribution stations use spread spectrum RF DA to monitor generating equipment and switching systems in high-EMI areas within plants.
On some systems, such as high-voltage platforms, cabling DA equipment to ground is not possible because of high potential differences. Spread spectrum modems connected to dataloggers and a PC can relay information in realtime from high-voltage platforms and distribution switches to control rooms to monitor equipment status.
Appliance manufacturers save time by using RF DA on moving assembly lines to test equipment performance during the manufacturing process. Appliances are monitored for performance as they move through various stages of manufacture. RF DA systems continually send information to production and quality stations that identify and track units that may need further inspection.
Automotive companies and alternative vehicle research groups use RF DA systems to monitor mobile vehicle tests during development. Using DA equipment connected to key points on a test vehicle and a global positioning system receiver, research teams can monitor performance under actual running conditions.
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