Wireless technology tips from Control Engineering wireless webcast
How about antennas with different frequencies?
What if antennas are handling different frequencies and modulations?
Antennas are cut or built to specific frequencies. They do not care about modulations.
Take your HDTV public signal: the same aerial antenna that you used with your old analog TV would work just fine. (The reason rabbit ears do not work as well is because the signal being transmitted is being transmitted horizontally and is extremely crisp. Rabbit ears are really designed for vertically RF transmitted signals.)
What are the main problems or challenges of wireless for industrial controls?
The two biggest challenges for applying wireless to industrial controls today are:
- Speed of response. If it is battery powered, you can only operate as fast as 1 second updates. This is not good for fast control like flow, but is usually okay for most level applications.
I have had many engineers use this technology for control. I have set up numerous SCADA [supervisory control and data acquisition] applications that are totally wireless dependent.
Free of cables? What about batteries? Reliability?
Are wireless field instrumentation devices completely free of cable? What about battery replacement and battery faults? Which is the normal life of the battery for a sensor for a fast process? What about interference over time in an ever-changing plant environment?
Radios typically use very little power. So here is where sensor technology comes into play.
Most sensors that are wireless independent will send out a warning sign prior to failure. But the speed and life of the battery is usually the field sensor issue and not the radio. The ISA100.11a and WirelessHART protocols have specifications that define the speed capabilities. Currently the fastest is 1 second for both. However, most manufacturer specs cannot achieve battery life greater than 3-5 years at that point. The longer you extend the sample rate, the longer your battery life will last. Many claim as long as 10 years for both.
My job is not to convince anyone of the technology but only to inform. As an engineer you need to evaluate the risks and make your own decisions on what is best for your facility. Being skeptical of a technology is a good thing as it will help you clearly evaluate what would be the next best move for your plant.
But I would like to mention something that may offer a window into the future and what a facility will look like in 10 years. Wireless technologies are very new to the industrial world. Wi-Fi (802.11) has only been released since 1997. In less than 10 years, it has become a common platform in almost every business sector, hotel, restaurant, etc. The technology has grown from its first release of IEEE 802.11a, which was solid and secure, to what we have today, which is IEEE 802.11, more than twice as fast, and many are convinced it is more reliable and secure than their Ethernet (CAT 5 Hardwire) network.
Moore’s law tells us that technology doubles every two years. So it is known that this technology will only improve with time. Technicians and engineers going through industrial engineering schools are already learning wireless technology. What you will see in the future is that your networks will be managed internally by extremely competent staff members. The need for a survey will not be necessary as the staff members will have their networks mapped out with a very specific strategy. The radio sets will only grow more robust in the future with forward and reverse capabilities for migration, and will take every element that you are concerned about into consideration.
Wireless will never take over every aspect of control or monitoring in a facility. It will probably never be used for any level of safety system or critical control. RF noise levels can easily be controlled in a facility and equally coexist with any changes from telecommunications systems at a neighboring plant today if properly installed initially without further changes. That is why I suggest that if you make your first move into this technology, it is always best to seek the wisdom of a group that can properly map out and plan your strategy.
Compare it to pneumatics over 4-20 mA wired technology. In the late 1980s, there were still many plants that had not adopted this technology, except in a few small areas due to skepticism, at an extremely high cost to their facilities. They continued to manage and maintain complex pneumatic systems riddled with moisture, leaks, and numerous other issues. But even those that did convert still use pneumatics throughout their facility in places that 4-20 mA or smart technology will never replace control valves.
A curiosity for learning new technology is a very good thing. This way, if and when you do decide to move forward, you will have all the proper information you need to build the right wireless strategy that offers significant cost savings to your plant while allowing no risk to currently well-managed wired application.
I appreciate all the feedback and questions. I also apologize for being less than dynamic in the presentation due to a bad flu bug. That is certainly not my normal performance.
- Stephen Muenstermann is RoviSys Building Technologies DC market manager. Edited by Mark T. Hoske, content manager, CFE Media, Control Engineering, mhoske(at)cfemedia.com.
See also, related PDF from Muenstermann’s part of the webcast, “Wireless technology tips from Control Engineering wireless webcast” in the webcast archive.
Also see www.controleng.com/wireless for additional information about industrial wireless.
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