Wireless Transmitters In Process Measurement and Control

Opportunities for cost effective wireless process control
connections are everywhere

In process control, different devices produce signals which represent flow, temperature, pressure, and other measurable elements of the control process. In order to travel from the measurement point to the point of decision, also known as the controller, systems have traditionally relied on wires. More recently, wireless networks used in industry have evolved, especially since point-to-point systems were introduced to process environments. The standard operating procedure today is known as the Wireless HART™ protocol, which features the same hallmarks of control and diagnostics featured in wired systems without an accompanying wire.

Wireless devices and wired devices can cohabitate the same network. The installation costs of wireless networks is vastly lower than wired networks due to the fact wireless networks need much less hardware. Wireless networks are also more efficient than their wired peers in regards to auxiliary measurements, involving measurement of substances at several points. Adding robustness to wireless, self-organizing networks is easy, because when new wireless components are introduced to a network, they can link to the existing network without needing to be reconfigured manually. Gateways can accommodate between 50 and 100 devices, allowing a very elastic range for expansion.

In a coal fired plant, plant operators walk a tightrope in monitoring multiple elements of the process. They calibrate limestone feed rates in conjunction with desulfurization systems, using target values determined experientially. The difficult process environment results from elevated slurry temperatures, and the associated pH sensors can only last for so long under such conditions. Thanks to the expandability of wireless transmitters, the incremental cost is reduced thanks to the flexibility of installation of new measurement loops. In regards to maintenance, the status of wireless devices are consistently transmitted alongside the process variables. Fewer manual checks are needed, and preventative measures are infrequent compared to wired networks. The minimization of overtime and staff instruction correlates with a maintenance of precise process control.

Time Synchronized Mesh Protocol (TSMP) ensures perfect timing for individual transmissions, which lets every transmitter’s radio and processor ‘rest’ between either sending or receiving a transmission. To compensate for the lack of a physical wire, in terms of security, wireless networks are equipped with a combination of authentication, encryption, verification, and key management. The amalgamation of those fail-safes makes for the security of wireless networks equal to that of a wired system. The multilayered approach, anchored by gateway key-management, presents a defense sequence. Thanks to the advancements in modern field networking technology, interference due to noise from other networks has been minimized to the point of being a rare concern. Even with the rarity, fail-safes are included in Wireless HART™.

All security functions are handled by the network autonomously, meaning manual configuration is unnecessary. In addition to process control environments, power plants will typically use two simultaneous wireless networks. Transmitters allow both safety showers and eyewash stations to trigger an alarm at the point of control when activated. Thanks to reduced cost, and their ease of applicability in environments challenging to wired systems, along with their developed performance and security, wireless instrumentation is altering process control environment monitoring for the better.

Analynk Wireless specializes in making wireless connections among process measurement and control equipment in the industrial arena.