Wireless Transmitters In Process Measurement and Control

Industrial process instrumentation connectivity can present
substantial challenges.

In process control, various devices produce signals which represent flow, temperature, pressure, and other measurable elements of the process. In delivering the process value from the measurement point to the point of decision, also known as the controller, systems have traditionally relied on wires. More recently, industrial wireless networks have evolved, though point-to-point wireless systems are still available and in use. A common operating protocol today is known as WirelessHART™ , which features the same hallmarks of control and diagnostics featured in wired systems without any accompanying cables.

Wireless devices and wired devices can co-exist on the same network. The installation costs of wireless networks are decidedly lower than wired networks due to the reduction in labor and materials for the wireless arrangement. 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 a large number of 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. A difficult process environment results from elevated slurry temperature, and the associated pH sensors can only last for a limited time under such conditions. Thanks to the expandability of wireless transmitters, the incremental cost is reduced thanks to the flexibility of installing new measurement loops. In regards to maintenance, the status of wireless devices is consistently transmitted alongside the process variable. Fewer manual checks are needed, and preventative measures may be reduced compared to wired networks.

Time Synchronized Mesh Protocol (TSMP) ensures correct 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 these security practices delivers wireless network security 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 WirelessHART™.

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 industrial connectivity will continue to expand.

Share your process measurement requirements and challenges with application specialists, combining your own process knowledge and experience with their product application expertise to develop effective solutions.

Dual Input Temperature Transmitter Has Some Useful Applications

Advanced Temperature Transmitter
Courtesy Azbil N.A.

Temperature measurement is a mainstay of many commercial and industrial processes and operations. Much can be deduced from an accurate measure of process temperature, and a large segment of the industrial control products marketplace is devoted to reliable and accurate measurement of temperature

There are a variety of instruments and methodologies for measuring temperature, the most common of which is probably direct contact between the substance under scrutiny and a temperature sensor of some type. In industrial process applications, contact sensors are often thermocouples or resistance temperature detectors (RTD), chosen for their cost, accuracy, and flexibility of installation.

Every operating process is "critical" to some group of stakeholders. The process may be of great importance for a number of reasons:

• The process output may serve as an input to another process with great value.
• The process output may be of great direct value to the stakeholders.
• The process may have significant levels of hazard associated with improper or out of control operation.
• Out of control operation may result in substantial financial loss to the stakeholders.

When temperature is an important indicator of process function, whether for financial or safety reasons, the operator cannot tolerate a loss of the temperature signal. One manufacturer has an advanced solution in the form of a dual input temperature transmitter with built in functions that:

• Switch to the backup sensor if the primary has a failure indication.
• Alert the operator if the deviation between the two sensor readings indicates sensor drift. 
• In wide range temperature applications, switch between sensors with differing measurement ranges for better accuracy.

Along with HART communications and other useful features, these advanced temperature transmitters can help reduce risk and increase performance and safety. Assess how these advanced devices can enhance your process performance. A product data sheet is included below. Product specialists can help with product configuration and selection, along with any application concerns you may have.

Advanced Industrial Temperature Transmitter from CTi Controltech