Remote - Winter 2012 - (Page 6)

Feature Article Automated Monitoring Out at the Network Edge Bill Conley, Cellular and Proprietary RF Device Product Manager B&B Electronics real-time data via GOES satellites. Other sites can use the fiber optic networks or ordinary copper Ethernet. But what happens when power and data infrastructure are not easily accessible? The USGS brought in remote-access data-communications experts from B&B Electronics to find a solution. Installing and servicing large battery arrays at these USGS data-collection sites would not have been cost-effective. The USGS needed an installation that could operate on a tight power budget in a remote location while maintaining reliable data communications. Satellite equipment would be too power-hungry for the intended application, so the answer would have to be radio. But even a radio installation needs power, so B&B had to decide how to provide each site with an independent power source. As a relatively mature technology, solar panels have become a reliable Groundwater Monitoring Challenges for the USGS power source for many kinds of remote installations. B&B determined the The United States Geological Survey (USGS), a science bureau within size and cost of the required solar panels by calculating the amount of powthe US Department of the Interior, has been one of the pioneers in remote er that would be needed at monitoring and data a particular location and reporting. The USGS aims comparing that number to to provide useful inforthe site’s solar insolation; mation to the public on the measure of solar energy the health of US ecosysreceived on a given surface tems and environment, area over a specified period the natural hazards that of time. threaten the country, and In a location like the impacts of climate and DeKalb County, Ill., where land-use change. For one B&B Electronics set up of its tasks, tracking and its first water monitoring reporting groundwater Figure 1. Figure 1 stations, the average yearly conditions all across the solar insolation level is United States, the USGS 3.72. (See Fig. 1) A typical sensor using an analog output might use 0.60 maintains a network of more than 9,500 sensor stations that measure river Sorting Out Radio Range and Power Budgets Amp hours per day (0.4 W by 24 hours at 12 V). A digital sensor might use flows, groundwater levels, water temperatures, rainfall and water quality. 0.72 Amp hours per day. If connected to an In the United States the standard license‐free radio frequencies are 900 MHz and 2.4 IP67-rated outdoor radio that Most such sensor stations are stationary. But others are mobile and can be required around 2.4 Amp hours per day, GHz. At 900 MHz you would theoretically have greater inherent range but less the total power requirement would deployed as needed during events like hurricanes and floods. In response to be 3.12 Amp hours per day, plus a reserve Hurricane Isaac, for example, the USGS set up several hundred mobile stabandwidth; at 2.4 GHz you would have more bandwidth, but also more multipath sufficient to charge and maintain a 12 V battery and keep the site functioning tions ranging as far as 100 miles from the projected path of the hurricane’s propagation, which occurs when intervening objects like trees or buildings absorb or during the dark hours. landfall, tracking data like storm surge and barometric pressure. reflect radio waves, causing them to arrive at the receiver at different times and out of It’s said that Christopher Columbus encountered a ferocious storm when returning from his first voyage to the Americas. Worried that news of his discoveries might be lost, he placed a report in a waterproof cask and set it adrift. In the end, Columbus survived the storm and brought his story home in person. His floating keg and its written report still haven’t turned up. Communications have become a bit more reliable since Columbus’ day. But as the network edge continues to expand, and as devices are being asked to function in increasingly harsh environments and in increasingly remote locations, network designers must find creative ways to keep data from disappearing like Christopher Columbus’ floating keg. but less bandwidth; at 2.4 GHz you would have more bandwidth, but also Data collected at USGS monitoring stations is posted on the USGS web range by up to 30%, and reducing the data rate can improve range. So without more multipath propagation, which occurs when intervening objects like site, where it is updated as part of the USGS’s WaterALERT program. Emertrees or buildings absorb or reflect radio waves, gency managers use the data examining the specific application, it was impossible for B&B Electronics to say which of causing them to arrive at to provide alerts when floodwaters are about the receiver at different times and out of sequence. Multipath propagation the license‐free frequencies would provide the better signal. to exceed safe levels, and to track chemical spills. Recreational rafters and makes it harder for the receiver to decode the signal. Additionally, as the kayakers use it to determine whether water levels are high enough to pass data rate of a system increases, the more the received signal is degraded by over rocks, but not so high asRadio is also affected by antenna gain, an antenna’s ability to focus the RF signal into a to pose a safety risk. In drought conditions, the electrical noise in the environment. Doubling water supply managers can view local data to decide whether it will be necnarrower, more useful, plane. This effectively increases the signal strength. A high‐gain the data rate can reduce range by up to 30 percent, and reducing the data essary to shut down supply pumps. All of these users can select specific data antenna doesn’t add energy to a signal or increase the power budget; it merely directs rate can improve range. So without examining the specific application, it was impossible for B&B parameters and instruct the web site to send a text or email notification any the radiated energy in a useful direction at the expense of the unwanted directions. Hi‐ Electronics to say which of the license-free frequencies would provide the time those parameters fall above or below specified thresholds, and there is gain antennas are quite useful when power budgets are a major consideration. better signal. no limit to the number of subscribers who may use the web site at the same Radio is also affected by antenna gain, an antenna’s ability to focus the time. Future enhancements will include nitrogen plume tracking and detecReceiver sensitivity, the measure of the minimum signal level at which a receiver is able This effectively increases RF signal into a narrower, more useful, plane. tion of where and when farmers are watering and/or fertilizing. to detect the RF signal and demodulate the signal strength. A high-gain antenna doesn’t add energy to a signal or But to make the system work, a typical USGS water-monitoring site the data, presents another opportunity to increase the power budget; it merely directs the radiated energy in a useful needs, at the very least, uncompensated pressure transducers to detect water direction at the expense of the unwanted directions. Hi-gain antennas are cut the power budget. Improved levels, and sensors to monitor water temperature. If data is to be reported in quite useful when power budgets are a major consideration. anything close to real time, the site will also need a reliable power source sensitivity saves power and extends Receiver sensitivity, the measure of the minimum signal level at which and a stable connection for data communications. range. a receiver is able to detect the RF signal and demodulate the data, presents another opportunity to cut the power budget. Improved sensitivity saves Calculating Power Budgets High‐quality antenna cable helps, too. power and extends range. In locations that have easy access to the power grid there are many ways Using low‐loss cable maintains the signal High-quality antenna cable helps, too. Using low-loss cable maintains to address these issues. In Illinois, for example, the USGS operates some level between the transmitter and the 240 data-collection sites and more than 100 of them are equipped to provide the signal level between the transmitter and the antenna, and the longer the Sorting Out Radio Range and Power sequence. Multipath propagation makes it harder for the receiver to decode the signal. Budgets In the US the standard license-free radio frequencies are 900 MHz and USGS’s WaterALERT Facilitates Decisions from Additionally, as the data rate of a system increases, the more the received signal is 2.4 GHz. At 900 MHz you would theoretically have greater inherent range Emergency to Recreation degraded by the electrical noise in the environment. Doubling the data rate can reduce antenna, and the longer the distance, the 6 www.RemoteMagazine.com http://www.RemoteMagazine.com

Table of Contents for the Digital Edition of Remote - Winter 2012

Remote - Winter 2012
Editor's Choice
Automated Monitoring Out at the Network Edge
What’s in Your Radio Communication Tackle Box?
When Does Solar Make Sense for Remote Sites?
Utility Networks in Transition
TV White-Space Technology Makes Broadband Affordable for Remote Locations
Challenges of Remote Management over Satellite
SCADA Market: Charting Strong Growth Amidst Industry Speculation
SCADA
Networking
Security
Oniste Power
Environmental Monitoring
Industry News

Remote - Winter 2012