The world is becoming more and more wireless. PC’s communicate with each other and to our printers while connecting us to the web via WiFi. Our mobile phones chat to PC’s and hands - free devices in cars via Bluetooth, while allowing us to talk to each other through thin air. So what about sensors and instrumentation?
Firstly, it’s important to distinguish what is meant by “wireless”. As we’ve already said, wireless seems to be everywhere with an ever increasing barrage of buzz words and jargon. So let’s take a look at what’s out there:
• Wireless Local Area Networks (WLAN): e.g. wireless Ethernet in an office environment
• Global Wireless Networks (WAN): e.g. gateways with GSM/UMTS communication
• Personal Area Networks (PAN): e.g. handhelds based on Bluetooth technology
• Wireless Industrial Sensor Networks (WSN): e.g. WirelessHART
In Endress + Hauser Australia’s business, when talking about wireless, it means WSN and more specifically WirelessHART.
Despite extensive marketing hype from some suppliers promoting the implementation of WirelessHart devices everywhere, the global standard for WSN is only just being finalised. Because of this, the technology is yet to be accepted for true plant control – this is still some time away. In fact, most existing wireless installations are actually ‘wired’ wireless which then raises the question – ‘Why do we need wireless at all?’
The ultimate benefit of ‘wireless’ is the total elimination of cables, so the only way to enjoy this benefit is with ‘true’ wireless which is the strategic direction taken by Endress+Hauser. However, in taking this direction, we have been forced to look at the issues of safety and reliability of wireless technology along with the responsible application of wireless devices in process industries. If the WiFi or Bluetooth link between the home computer and printer fails and you can’t print a document it’s annoying, but what if a level sensor fails to communicate the ‘high high’ alarm in a tank of sulphuric acid to a plant’s control system? The results could be catastrophic.
In view of potential catastrophic failures, a common concern amongst potential users is the vulnerability of wireless communications to malicious “wireless jamming”. One only has to do an internet search for “wireless jammer” to be astounded at the availability and low cost of these wireless jammers. This concern is likely to limit acceptance of wireless to only monitoring rather than control and safety applications.
It’s estimated that 70 to 80% of all measuring devices in a typical process plant or tank farm are loop powered. Not all measurements are critical to safe plant operation; many relate to monitoring and inventory control. The devices making these non-critical measurements are ideally suited to ‘true’ wireless.