Wireless Sensor Networks For Industrial Automation
Wireless Sensor Networks (WSN) for industrial automation and applications are becoming more prevalent in most industrial industry segments.
Mature industries such as Refineries (Oil and Gas), Water (Waste Treatment and Delivery) and Energy (Electrical Generation, Natural Gas Distribution) have migrated from wired to wireless sensor networks over the past decades to take advantage of the cost benefits and infrastructure advancements. New industries in Healthcare, Hospitals and Green Energy are implementing wireless sensor networks and arrays in novel applications.
At its most basic level, a WSN is simply a grouping of sensors which are intelligently connected to a network through a series of bridges, switches, routers and gateways. The sensors, or nodes, monitor and report one or more physical parameters such as: Temperature, Pressure, Fluid or Material Level, Flow Rates, pH Level, Acceleration, Motion, Vibration, Humidity, Light, Proximity and Position.
The node usually has its own power source, an analog to digital converter and a transmitter. in addition to the actual sensor element. A more complex node may have two way communications with the network as well as built in processing capabilities.
There are a number of challenges in migrating from a wired to a wireless sensor network. The coverage area of the network may suffer in the industrial environment due to various interferences. The reliability and the signal strength may get affected due to the reflection from the walls, interference from other devices or machines, and interference from the environment itself.
Other challenges in deciding on a wireless network are:
- Selection of the sensors and node elements
- Interoperability of multiple vendor equipment for nodes, routers and gateways
- Industrial Grade Environmental ratings for all equipment in the network
- Deployable number of node elements and network size
- Data throughput of the network
- Time delay through the network from sensor to monitoring site
- Continuous change in wireless standards
- Frequency to communicate in
- Data integrity
- Network Security
In 2006, according to the survey which was done by Hoske, the best applications for industrial automation were in the area of supervisory control and data acquisition (SCADA). SCADA implementations were able to replace direct human involvement in a system with automation. This reduced overall costs, eliminated personal risks and provided a more robust solution. Automation was now possible through the use of sensors and feed back controls.
Specific to industrial automation, wireless systems are increasing in the areas of :
- System Control and Monitoring
- Real Time Data Collection
- Mobile and Stationary Robots
- Rare Event Detection
- Periodic Data Collection
Despite the challenges mentioned earlier, there are a number of compelling reasons to implement a wireless sensor network instead of a wired network. Most notably is that in an industrial automation environment it is often impractical or even hazardous to run wires and cables to sensors. Often the cost of the physical wire and installation will far exceed that of the entire wireless sensor network. Wire is also subject to cuts, breaks and degradation over age especially in harsh industrial environments. In some cases, it may not be possible to use wires either due to zoning restrictions, physical obstructions or lengthy distances.
In general, the advantages of a wireless sensor network are:
- Flexibility of Installation
- Reduced Maintenance Costs
- Decentralization of the Network
- Fault Detection and Repair
Industrial automation in general, and wireless sensor networks specifically, continues to be a developing an growing market. There are a number of providers of sensors and network communications equipment. For sensors, the major solutions and semiconductor manufacturers are:
Nordic Semiconductor is focused on providing ultra low power (ULP) wireless products, and their product portfolio is centered on wireless communications in the 2.4 GHz and sub 1 GHz (433 MHz, 868 MHz, 915 MHz) frequency bands.
Digi International is unique in the list above in that they provide a complete end-to-end solution which includes the nodes, wireless transceivers, routers and gateways, and a cloud service to monitor the wireless sensor network. They can also incorporate sensors and nodes from other vendors to create a completely inter-operable system.
For more information on the topic of wireless sensors, please see our related articles on this site.
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