Advance Efficiency With Digital Communication

Modern smart instrumentation solutions provide diagnostic information that empowers informed decision making and proactive maintenance.

By Fabrício de Andrade, Endress+Hauser

For decades, control-system instrument data was constrained to single analog process variables communicated through individual 4-to-20-mA current loops. Modern instrumentation advances, particularly digital communications, now provide a wealth of additional diagnostic and other information, enabling operational insights unachievable with simple 4-to-20-mA measurements alone. This extended data helps plant personnel improve operational efficiency and avoid unplanned shutdowns by empowering them to implement proactive maintenance, in addition to simplifying calibration procedures.

Modern device-level network media options, such as HART over 4-to-20 mA, WirelessHART, Ethernet-APL, and Bluetooth, provide the ability to transmit data bi-directionally between an instrument and its host system. Various communication methods are selected, based on the target field devices, and depending on the intended application.

For wired installations, plants can implement a combination of HART over 4-to-20 mA and Ethernet-APL, enabling them to update legacy installations and take advantage of newer, fully digital technology, depending on project needs. For instruments in hard-to-reach and hazardous locations, WirelessHART and Bluetooth options enable wireless transmission of multiple process variables and diagnostic data to a wide variety of host systems, providing even more flexibility for handling instrument data.

Ethernet-APL architecture is highly customizable, requiring only a gateway and power supply to enable data transfer among a wide range of instruments and various host systems using a single two-wire shielded cable per instrument. All figures courtesy of Endress+Hauser

Traditional challenges

There are many factors that affect and even interfere with the accuracy of a traditional instrument’s analog output. Operators interpreting such a signal processed by a programmable logic controller, distributed-control system, asset-management system, or other host system, simply have no other information regarding accuracy. Each analog loop scales a single process value as electrical current, unable to transmit secondary variables such as temperature on a pressure instrument. Additionally, communication is unidirectional only, so there is no way to send commands from a host to the instrument.

Traditional analog instrumentation also lacks diagnostic information, making it nearly impossible to foresee or troubleshoot instrument failure. Malfunctions cause unplanned downtime and costly instrumentation repairs in the best cases, or catastrophic equipment damage and safety hazards in the worst. Bound by analog electronics, traditional instruments must be hardwired to a host system, limiting placement in hard-to-reach areas of a facility, and especially in offsite remote locations.

Digital paths to connectivity 

Digital communication methods increase data availability and provide data-processing flexibility so plant personnel can make informed operational and maintenance decisions. Plant designs featuring smart instrumentation using digital protocols make facility operation and optimization much more manageable. Following are four modern protocols and transport media that increase instrumentation value and control system capabilities.

HART over 4-to-20 mA: For retrofitted and new applications where hardwiring transmitters back to a host system is existing or convenient, instruments can use the bi-directional digital HART communication protocol, which is superimposed on a 4-to-20-mA analog current loop. This enables sending and receiving data between an instrument communicator and a host system. The exchanged data includes primary process values, one or more secondary process values, and diagnostics, calibration, and maintenance information. This wealth of data makes configuration easy and improves operational process insights, compared to traditional analog-only instrumentation.

Because HART-enabled instruments can transmit multiple process values to a controller through a single loop, users gain flexibility to continue using existing analog loops for real-time control, while taking advantage of transmitting additional process and diagnostic data to the host system to aid in making data-driven decisions within a facility.

WirelessHART and Bluetooth: Where wired implementations are impossible or inconvenient, wireless smart instruments provide solutions through 2.4-GHz radio-wave technologies and protocols, notably WirelessHART and Bluetooth. Many smart instruments provide these connectivity options natively, while adapters can be added to provide this functionality for those that do not. These capabilities can be used to create a mesh network of sensors around a plant and in the field.

WirelessHART and Bluetooth instruments typically send and receive as much or more diagnostic and process data as their wired HART counterparts. While this data can provide immense benefits to a wide range of host systems and applications—such as maintenance management, asset information and health management, inventory control, and enterprise resource planning systems—many facilities do not yet take full advantage of what this data has to offer.

Ethernet-APL: A more recent development is the Ethernet-APL physical transport layer. It provides the ability to transmit digital data via industrial Ethernet protocols using a single two-wired shielded cable per instrument. With the same cable requirements as HART—though markedly different gateway and termination specifications—Ethernet-APL can simplify retrofits by eliminating the need to pull new wires to instruments.

The Ethernet-APL physical layer is protocol agnostic and supports industrial protocols such as PROFINET, EtherNet/IP, Modbus TCP, HART-IP, OPC UA, and other higher-level network protocols. Ethernet-APL provides high-speed data transmission at a 10Mbit/sec. data rate, making it possible to send and receive more data than can be transmitted with older digital methods. This provides a robust basis for continuous diagnostics, monitoring, industrial internet of things (IIoT) connectivity, and remote instrumentation verification.

Because communication is handled with standard Ethernet protocols, instrument data routing among process-control systems and asset-management tools is highly efficient in modern control environments already using these protocols.

As a foundational transport layer, Ethernet-APL is capable of carrying any industrial Ethernet protocol. Endress+Hauser Ethernet-APL instrumentation currently supports PROFINET traffic, with plans to carry EtherNet/IP, Modbus TCP, and additional protocols in the near future.

Data and operational optimization

Control systems regularly use flow, pressure, temperature, level, and other measured values to monitor and control processes, but they often discard or lack access to status and diagnostic data. By not using this supplementary information, facilities miss out on opportunities to optimize, simplify, and safeguard their plant operations.

Instead, if this data can be ingested by intelligent plant-analysis systems, facilities are able to increase their ratio of proactive to reactive maintenance, reduce unplanned downtime, and minimize equipment and human safety hazards. For example, instead of waiting for an alert indicating a high-temperature condition, process data can be used to provide a preemptive notification when conditions are detected that would lead to this type of issue, if left unmitigated.

Data can also be analyzed to provide advance warning of instrument failure or troubleshooting insight in the event of failure. Additionally, tracking and managing assets becomes easier throughout plant lifecycles because calibration and nameplate information for many modern smart instruments is also recorded.

Cloud-based add-ons

Plant managers can extend digital instrument insights even further by leveraging cloud connectivity and computing to perform advanced analysis, data storage, archival, and retrieval functions. Comprehensive insights help develop maintenance plans to organize shutdowns and evolve maintenance procedures from corrective to predictive. Additional cloud-based tools can be used to generate process optimization insights, identifying parameter changes and strategy adjustments that can lead to improved operational efficiency.

Digital advancements

To optimize plant processes, implementing digital protocols and smart instrumentation provides indispensable data for host systems that can be used to create operational and maintenance insights. Two-way communication from smart instruments to host systems provides multivariable process values and extensive diagnostic information.

Insights derived in this manner help users improve process efficiency and assist in avoiding unplanned shutdowns by aiding the development of proactive maintenance procedures. Data can be reviewed locally at a facility and expanded to the cloud so insights can be accessed remotely by external support personnel and process experts. This can further increase an organization’s productivity and response speed when issues arise.

Whether an organization is well along on their digitalization journey or just beginning, it is undeniable that industry reliance on digital data and IIoT technology is becoming more pronounced. By deploying network infrastructure and smart instrumentation throughout their enterprises, companies are better prepared to continuously optimize their processes and remain competitive in the digital age. EP

Fabrício de Andrade is an IIoT Business Development Manager at Endress+Hauser Digital Solutions in Switzerland. He is responsible for IIoT in Latin America, Mexico, Spain, and Portugal. He graduated in business management, and holds an MBA in Marketing and Digital Business, in addition to a degree in Process Automation and Telecommunication.