|
Wireless
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. Data logger 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.
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.
- 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.
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 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 fiber-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 data loggers and a PC can
relay information in real time 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.
Learn More
For additional information about the Sensor Industry and the
role of wireless in data acquisition systems, see Sensors
Magazine online.
|
