Implementing wireless solutions for industrial communication applications

Wireless technology has limitations, but like any technology, it is very powerful when properly applied. Consider these factors before implementing wireless devices, including power, response time, and range, among others.

By Bob Gardner May 24, 2012

With today’s diverse industrial application operations and procedures, manufacturers are turning to wireless networks for their communication requirements. Wireless networks allow robust monitoring and control, even in remote and harsh applications or classified areas. Wireless network systems enhance industrial communication capabilities, allowing manufacturers to increase overall efficiency and productivity. By eliminating the wire limitations of conventional systems, wireless networking systems provide improved data logging, process monitoring, and control, while maintaining the highest level of security and integrity.

Today’s advanced communication technologies can integrate with almost any industrial application. With their highly diverse performance capabilities, such as temperature, pressure, control, and position detection as well as error proofing and machine monitoring, wireless systems can seamlessly meet manufacturers’ ever-evolving requirements.

4 wireless considerations

Before using wireless, consider this:

Wireless technology has limitations, but like any technology, it is very powerful when properly applied. Here are a few factors to consider before implementing wireless devices:

1. Is power available remotely? Wireless signals require very little power, allowing remote locations to be monitored where there is no power. However, the sensor used in these applications also must run on low power. Today, technology can sense many things with low power, including temperature, pressure, dry contacts, inductive, and photoelectric proximity sensors. All these sensors can operate for years on inexpensive AA batteries. If another source of power is used remotely (line or solar), any type of sensor can be used.

2. How fast do you need a response? This issue is tightly coupled with the power issue. If there is power available, the sensor and wireless transmitter can always be “on.”  This allows for real-time control and less than one second response times. If power is unavailable, it is important to balance the desired response time with the available battery life. For example, if you measure and report the temperature of a remote location every one minute, you might have a 1-year battery life. Alternatively, if you slow to 15-minute intervals, you might have a 10-year battery life. Faster is not always better when using battery-powered operation.

3. What kind of wireless range do you need? Wireless solutions exist that can transmit many miles of "line of sight" or across an entire large factory. Selecting a long-range system will simplify the design by eliminating repeaters. It will also provide flexibility for adding additional nodes in the future.

4. What happens when a wireless link is lost? While properly designed wireless systems are very reliable, it is crucial to consider what happens when a link goes down: the system should fail gracefully. For first-time wireless users, it is best to start with a non-mission-critical task. If the link is lost, the outputs should automatically go to a predefined state.

When to go wireless

Manufacturers should consider using wireless when it provides a cost-efficient, reliable alternative to other solutions. When taking into account these factors, wireless is suitable for applications that:

  • Have slow response time needs of 0.5 second to many minutes (consider battery life trade-off)
  • The cost of wiring is expensive

Wireless technology is an ideal option when the cost of wiring becomes prohibitive in industrial applications. This happens when:

  • There are long or multiple wire runs, for example, of more than 50 ft
  • There are slip rings or cable tracks
  • Wire runs need to go through floors or walls
  • End points are in motion or can be reconfigured frequently 

Applications that present the above factors, making them optimal for wireless use, include: call for parts, monitoring or displaying machine or line status, rotary or mobile text fixtures, and AGVs.

Wireless pre-integration

Today, many remote monitoring solutions are available that offer more reliable wireless communication, while integrating a number of components (RTU, radio, solar panel, and rechargeable battery pack, as well as input and output terminals) into one, inexpensive unit. A radio and I/O terminal contained within one housing that is rated for outdoor use eliminates the need for an additional enclosure. Without this large, permanent enclosure, these new wireless industrial I/O devices are easy to install, and then uninstall and move to a new location as monitoring requirements change.

With the radio, power controller, I/O terminals, and RTU components included within one water-resistant housing, fewer mechanical and wiring issues need to be incorporated into a maintenance schedule, resulting in valuable time and cost savings—without sacrificing capabilities. One wireless I/O device can collect digital and analog sensor readings and forward data to a central collection point for analysis.

Next wireless application

Applications include remote monitoring and process control, among others.

– Remote monitoring: Wireless remote I/O is particularly suitable for small, single-point measurements, such as monitoring motor temperatures in isolated locations. While previous remote monitoring technology was too expensive or too bulky to use for low-signal count applications, current technology makes these applications easy to install and use regardless of scale. For example, a wireless I/O device and power-optimized temperature sensor can reliably monitor motor temperatures and report the measurements to a central location. The “peel and stick” installation allows this device to be easily moved and reinstalled depending on the requirements of the application.

Because these devices are more compact than past systems and are certified for a wide variety of environments, they are easy to retrofit into existing applications, particularly on mobile assets, such as trucks or boats that must enter and exit hazardous locations or areas rated to require intrinsically safe equipment. These devices can be installed in a broad range of environmental conditions ranging from outdoor installations exposed to weather to applications within hazardous or explosive locations.

– Process control: Wireless industrial I/O monitoring also offers reliable operation for process control applications. For example, maintenance personnel at a commercial printing company are required to take continuous level readings throughout their on-site water treatment process to comply with state mandates. A dedicated maintenance person was needed to manually sample and document each individual level at regularly scheduled intervals. Although this data was collected, it was isolated from the plant-wide control system and had to be reviewed at the end of each shift.

A wireless network is installed to take level readings throughout the water treatment process. A node with analog inputs takes each water level measurement point and transmits this data back to the maintenance shop, located in a separate building. The level data is automatically sampled and can be reviewed in real time. Without increasing maintenance personnel, the company was able to focus on other outstanding issues and still reliably collect the water level data needed to comply with standard water treatment practices. Further, wireless technology increased visibility and logging capabilities throughout their water treatment process.

– Your next implementation: Whether an application needs to be a cost-effective solution for single-point monitoring or scalable up to 10,000 data points, wireless products and sensors offer reduced installation time, multi-year battery life, reliable radio communications, and simple integration into existing plant-wide control systems.

– Bob Gardner is senior product manager, Banner Engineering. Edited by Mark T. Hoske, content manager CFE Media, Control Engineering, Plant Engineering, and Consulting-Specifying Engineer,