HART (Highway Addressable Remote Transducer) is one of the most widely used communication protocols in industrial automation. It allows digital communication between field instruments and control or monitoring systems, while still supporting legacy 4-20mA analog signals. Over time, several versions of HART have been developed, each offering new features and enhancements to meet the evolving needs of industrial applications. Let’s dive deeper into each version of HART, highlighting the key functions and distinctions that make each iteration unique.
1. HART 5 (HART v5): The Foundation of HART Technology
- Released: 1986
- Key Features:
- HART 5 represents the first iteration of the protocol, built to support communication over standard 4-20mA current loops. It allows digital data to be overlaid on the analog signal using Frequency Shift Keying (FSK).
- The protocol supports bidirectional communication, meaning that field devices such as transmitters and controllers can both send and receive data. This feature makes HART useful for both monitoring and configuring devices.
- One key characteristic is its ability to poll multiple devices on a single communication line (multidrop mode), allowing up to 15 devices to be connected and communicate without requiring separate wiring.
- HART 5 operates at a communication rate of 1200 bits per second (bps), which, though slow by today’s standards, was sufficient for transmitting key process variables like pressure, temperature, or flow data.
- Use Case: HART 5 is well-suited to early industrial automation systems that required enhanced device communication without needing to replace existing analog systems. Its ability to coexist with 4-20mA systems made it popular for retrofitting older plants with minimal disruption.
2. HART 6 (HART v6): Enhancing Device Management and Diagnostics
- Released: 2001
- Key Features:
- HART 6 brought significant advancements to the protocol, particularly in the areas of device management and diagnostics. The protocol introduced enhanced capabilities to automatically identify connected devices, reducing manual configuration.
- One of the standout features of HART 6 is its ability to transmit multiple process variables (multi-variable communication). This allows a single HART device, such as a flow meter, to send data about flow rate, temperature, and pressure simultaneously.
- This version also expanded the command set and introduced longer message frames. These improvements enabled the transmission of more detailed information, such as device status, configuration settings, and maintenance data, enhancing asset management and predictive maintenance.
- Expanded diagnostics, including status alerts and event logging, allowed operators to monitor not only process values but also the health of the devices themselves. This made HART 6 especially valuable in environments where minimizing downtime and optimizing equipment performance were critical.
- Use Case: HART 6 is ideal for plants that need improved diagnostic capabilities and wish to manage their devices more effectively, particularly in process industries such as oil and gas, chemical processing, and pharmaceuticals.
3. HART 7 (HART v7): Introducing Wireless Communication with WirelessHART
- Released: 2007
- Key Features:
- The introduction of HART 7 marked a pivotal moment in the evolution of industrial communication with the advent of WirelessHART. This version extended the protocol’s capabilities to wireless networks, making it easier to install, configure, and maintain devices in difficult-to-wire or hazardous environments.
- WirelessHART uses mesh networking technology, where devices communicate with each other and can act as relays to pass data along. This self-organizing and self-healing network ensures reliable communication, even if some devices or communication paths become unavailable.
- HART 7 expanded security features, with built-in encryption and authentication to protect against unauthorized access and data tampering, which is critical in industrial settings.
- Time synchronization across devices and support for higher device counts further enhanced the scalability and reliability of wireless networks.
- This version also enhanced reporting of events and diagnostics, providing real-time visibility into the state of field devices and making WirelessHART networks suitable for both critical process control and asset management applications.
- Use Case: WirelessHART networks are particularly useful in modern industrial environments that need to reduce wiring costs, such as large-scale plants, refineries, and offshore platforms, where cabling might be expensive or impractical.
4. HART 8 (HART-IP): The Protocol for Industrial IoT
- Released: 2020
- Key Features:
- HART 8, also known as HART-IP, represents the latest evolution of the protocol, aligning it with the growing demands of the Industrial Internet of Things (IIoT). This version extends the HART protocol to work over Internet Protocol (IP) networks, enabling seamless communication between HART devices and higher-level systems such as cloud platforms or enterprise databases.
- HART-IP allows for much faster communication rates compared to traditional HART communication, making it suitable for applications that require the transmission of large amounts of data or frequent data updates.
- By utilizing standard Ethernet infrastructure, HART-IP enables industrial devices to be easily integrated with modern IT systems, cloud services, and big data analytics platforms, facilitating smarter and more data-driven decision-making in industrial operations.
- HART-IP is designed to be fully backward-compatible with existing HART networks, meaning that plants can integrate new HART-IP-enabled devices without needing to replace their entire communication infrastructure.
- The protocol also supports enhanced security measures, such as encryption, data integrity checks, and secure network management, ensuring that communication is safeguarded against cyber threats.
- Use Case: HART-IP is designed for forward-thinking industries looking to implement IIoT solutions, where connectivity, data analytics, and cloud integration are essential. It’s especially valuable for organizations aiming to leverage real-time data for predictive maintenance, operational optimization, and smart manufacturing.
Key Differences Between HART Versions
- Communication Medium: The main leap in HART 7 was the introduction of wireless communication, while HART 8 built on this by integrating with modern IP networks.
- Diagnostic and Management Capabilities: HART 6 and HART 7 significantly expanded the ability to monitor the health of devices and provided richer diagnostic data.
- Security Enhancements: HART 7 introduced wireless encryption, and HART 8 added further cyber security features to protect data in digital industrial environments.
- Data Transmission: HART 5 supports basic digital communication, while HART 6 and later versions introduced multi-variable transmission, allowing more data to be transmitted simultaneously.
- Compatibility: Each version of HART has remained backward-compatible, ensuring that older devices can still communicate within upgraded systems.
Conclusion
The evolution of the HART protocol from its foundational HART 5 version to the current HART 8 (HART-IP) demonstrates the adaptability of this technology to meet the changing needs of industrial automation.
With each new version, HART has expanded its capabilities to include enhanced diagnostics, wireless communication, and integration with modern IP networks, making it a cornerstone technology in the Industrial Internet of Things (IIoT).
Whether for basic field device communication or sophisticated smart factory solutions, HART continues to evolve and remain relevant in a rapidly digitizing industrial world.