Overview
Developed to replace, expand and enhance centralized parallel wiring for prevailing analog and SDI-12 signal transmissions, sensorBUS technology simplifies the creation of environmental monitoring networks by combining several popular sensor interface types on a single 8-wire bus.
sensorBUS is mainly used at the field level with interfacing capabilities to smart sensors that incorporate 1-wire temp string, RS-485 multi-drop or SDI-12 hardware/software connection. sensorBUS is the solution for linking multiple sensors using open, standardized technologies.
The benefits to environmental monitoring projects are significant. sensorBUS can provide optimal solutions, by:
1. saving time and money during planning, installation, commissioning, operation, and maintenance
2. requiring much less space, fewer components and greatly simplified sensor connections
3. providing freedom to stay with favorite sensor vendors or select products from new vendors
4. providing environmental technologist with a totally new sense of involvement through a plug-and-play system design that does not require the support of a an electronic engineering or computer technology company
5. providing an open communications standard, an extensive range of compliant products, and unified technology including reusable sensor drivers
sensorBUS Hardware Architecture
sensorBUS includes three industry standard digital interfaces (1-wire temp string, RS-485 multi-drop and SDI-12) along with both 12 and 5VDC power.
1-wire temp string is a multi-point communications network capable of supporting 128 temperature measurement nodes (sensors) over 200 meters. Data is transmitted and received on a single wire. 1-wire temp string communication is between master (data logger) and slaves (smart sensor), communicating at 9600 baud.
RS-485 is a multi-point communications network capable of supporting hundreds of nodes (sensors) over a few thousand feet. The balanced 2-wire system is constructed with a twisted pair of conductors surrounded by a shield. RS-485 communication is between master (data logger) and slaves (smart sensor), communicating at 1200 to 57,600 baud.
SDI-12 is a serial data interface capable of supporting up to 10 sensors. The 3-wire system includes 12VDC, Ground and SDI data signals. SDI-12 communication is between master (data logger) and slaves (smart sensor), communicating at 1200 baud.
Cables and Connectors
The field rugged, watertight connector/cable system (Figure 1) is designed for harsh environment and submersible (fresh, brackish or salt water) applications. The cable is constructed of (8) 22 AWG wires, including a shielded twisted pair for RS-485 signals, an overall shield and a heavy wall, UV stabilized poly-urethane jacket. Connectorized cable ends include a flexible strain-relief and either a plug (Figure 2) or receptacle (Figure 3) fitting.
Double o-rings (both gland and face seals) ensure a reliable and water-tight connection. Mated connectors are rated at 500 meters of submersion. Cables are interchangeable and can be connected in series to extend lengths as needed. A complete set of accessories are available for termination, junction and signal splitting.
Constructing a multi-point temperature string (Figure 4)
sensorBUS simplifies the design, setup and operation of multi-point temperature strings. Determine the number of temperature points and spacing. Connect temperature nodes and cable together and connect the top cable to the data logger sensorBUS port. For floating platform applications, the temperature string can be suspended from a data buoy. A multitude of data telemetry options (Ethernet, Phone line, Spread Spectrum Radio, RS232, and Cellular) are available, as well as data-to-website capabilities.
Constructing a multi-point water quality sensor string (Figure 5)
sensorBUS simplifies the design, setup and operation of multi-point water quality strings. Determine the number water quality monitoring points and spacing. Connect cable slitters and cable together and connect the top cable to the data logger sensorBUS port. Connect multi-parameter water quality sondes to the cable splitters. For floating platform applications, suspend the water quality string from a data buoy. A multitude of data telemetry options (Ethernet, Phone line, Spread Spectrum Radio, RS232, and Cellular) are available, as well as data-to-website capabilities.
Constructing a multi-point temperature and dissolved oxygen string (Figure 6)
sensorBUS simplifies the design, setup and operation of multi-point temperature and dissolved oxygen strings. Determine the number temperature and dissolved oxygen monitoring points and spacing. Connect temperature nodes, cable slitters and cable together and connect the top cable to the data logger sensorBUS port. Connect dissolved oxygen sensors to the cable splitters. For floating platform applications, suspend the water quality string from a data buoy. A multitude of data telemetry options (Ethernet, Phone line, Spread Spectrum Radio, RS232, and Cellular) are available, as well as data-to-website capabilities.
Data Logging and Telemetry
At the heart of an environmental monitoring system is a battery operated data logger, which is typically located on shore or on a data buoy. Shore-side systems can be pole mounted, or housed in a secondary building or enclosure. Figure 4 shows a pole mounted NexSens iSIC Data Logger near a drinking water intake. The data logger stores environmental data at a specified time interval.
When configured with telemetry, data can be transmitted from remote sites to a project computer. Figure 2 shows a NexSens 3100-iSIC Cellular Data Logger housed in a corrosion resistant stainless steel enclosure and mounted at a bridge site.
Two factors help determine the best telemetry method: site conditions and distance to a base computer. When the project computer can be located within a few miles (line-of-site) or few hundred feet (non-line-of-site), license free spread spectrum radio telemetry, such as the NexSens 4100-iSIC Data Logger and 4100-Base Radio is the best choice. The distance can be extended with use of repeaters, which for the NexSens system is simply an additional 4100-iSIC. When the project site is remotely located, relative to the project computer, cellular telemetry becomes the best option. The NexSens 3100-iSIC Cellular Data Logger is easily configured for various cellular providers and supports GSM/GPRS, CDMA, EV-DO, iDEN and EDGE technologies on all major cellular service provider networks such as Verizon, Cingular/AT&T, and Sprint/Nextel. Cellular signal strengths should be confirmed during the site survey and before setting up a cellular data account. When cellular signals are weak a NexSens 2100-iSIC Phone Data Logger, NexSens 3200-iSIC Cellular-Radio, NexSens 5200-iSIC Ethernet-Radio or a NexSens 4200-iSIC Phone-Radio Data Logger should be considered.
Also available is the new SDL-500 Submersible Data Logger. Designed for floodplain, lake, sea or river bottom, subsurface, and wave-zone deployments, the SDL-500 offers extreme environment data logging for environmental monitoring applications. This battery operated system offers all of the standard iSIC features in a rugged submersible housing.
Software
NexSens iChart software is a Windows based program, which simplifies and automates many of the tasks associated with acquiring, processing, analyzing and publishing environmental monitoring data. iChart has an extensive library of predefined device drivers for popular water level sensors. New monitoring devices are quickly configured by selecting from a drop-down list of manufacturers. There is no complicated programming required to set up data loggers and real-time monitoring networks. Simply choose a sensor, select a telemetry option, and your computer is ready to begin retrieving data. Data processing, reporting, exporting and sharing is automated and easy. One button export to Microsoft Excel and Adobe PDF are notable features.
Web Datacenter and Web Data Applets
WQData is a secure web datacenter providing an online interface for viewing gauge station data. It offers 24/7 instant access to project data using any web browser. Specifically designed for environmental monitoring applications, WQData is easy to setup and maintain. Your project specific web datacenter is automatically generated by iChart software and posted to the NexSens servers. The datacenter can be setup as a secure (password protected) site or an open site for easy access by anyone with the web address.
Included with WQData is the NexSens Web-Data Applet. Simply embed the applet code on your webpage to present website visitors with project data. An 'ALL DATA' button on the applet directs the visitor to the project datacenter where project maps, data, tables, graphs, statistics and other data visualization tools provide a professional and fully featured project website. An integrated project forum allows all team members to communicate and share information.
