TABLE OF CONTENTS

1. What is the HART protocol?
2. How HART protocol work?
3. HART Characteristics
4. HART Commands
5. What configuration do I need in a Rheonics HART device?
- 5.1. Short address
- 5.2. HART communication devices
6. Does Rheonics inline viscosity and density meter support HART?
7. How does Rheonics support HART integration and development?
8. REFERENCES

1. What is the HART protocol?

“HART" is an acronym for Highway Addressable Remote Transducer. The HART Protocol superimposes digital communication signals at a low level on top of a 4-20mA signal using the Frequency Shift Keying (FSK) standard.

The HART protocol is used worldwide to send and receive digital information on analog current loops (4-20 mA) between field instruments and distributed control systems.[1]

2. How HART protocol work?

Using the same 4-20mA wiring used for analog communications in Channel 1 from the Rheonics SME, a digital signal is encoded with a technique known as Frequency Shift Keying(FSK). Data from the digital signal includes PV, status, diagnostics, and additional measurements or calculations.

Figure 1. Signal modulation over 4-20mA [2]

In FSK, the digital information is encoded by shifting the frequency of the carrier signal between two predefined frequencies. In the case of HART, these frequencies are typically 1200 Hz (mark frequency) and 2200 Hz (space frequency). By toggling between these two frequencies, HART devices can transmit digital data over the analog current loop without interfering with the primary 4-20mA current signal used for process control. This allows for bi-directional communication, enabling configuration, monitoring, and diagnostics of field instruments in industrial applications.

3. HART Characteristics

HART allows analog and digital signals to be transmitted over the same two-wire connection.
It is possible to send data from control systems to field devices in a bi-directional manner using HART. Using this technology, field devices can be configured, calibrated, and diagnosed remotely.
The HART protocol is backward-compatible with older field devices since it is often used in conjunction with existing 4-20 mA analog systems.
Communication distances can reach several kilometers with HART system, depending on the quality of the cables and the number of devices connected to the loop. According to HART protocol theory, the maximum distance is 10,000 feet (3,000 meters).
A field instrument on a network can easily be identified and addressed by using a HART device address.
HART supports remote monitoring and diagnostics of field devices, enabling predictive maintenance and troubleshooting, thereby reducing maintenance costs and downtime.
It requires a loop resistance of a minimum 250Ω, two purposes are achieved by the resistance - it converts current-based HART signals to voltage signals, and it prevents the loop power supply from canceling the HART signals.

Figure 2. HART Topology with Rheonics Sensor

4. HART Commands

According to the HART Protocol, all communication takes place through a request (or command) from the host communication device during normal operation. For example, the host may be a PLC, distributed control system, or a PC-based asset management system.

Figure 3. HART command list.

5. What configuration do I need in a Rheonics HART device?

5.1. Short address

Rheonics sensor by default is set to a polling address 0, this can be edited at any time by the Rheonics Support time when applications with multidrop devices are needed.

5.2. HART communication devices

,Common devices that are used for HART communication are PLC, DCS, HART modem and HART communication.

5.2.1. PLC

A Programmable Logic Controller (PLC) is a digital computer that uses inputs and outputs to automate industrial processes. HART communication requires special hardware, which is not available in every analog card used in PLCs. Therefore, it is important to select the right analog card when the application requires HART communication.

Some examples of HART analog input cards:

5.2.1.1. Siemens/ET 200SP HA

The Siemens SIMATIC ET 200SP HA Interface Module IM 155-6 PN HA supports HART communication.

Figure 4. Analog card with HART-compatible SIMATIC ET 200SP HA[2]

5.2.1.2. Allen-Bradley/ControlLogix HART I/O Modules

These modules are designed to maximize system performance by combining real-time HART data with standard analog data. They're part of the Allen-Bradley/Rockwell Automation brand.

Figure 5. ControlLogix HART I/O Modules[3]

5.2.1.3. Emerson/RX3i Analog Input module, HART

This HART module has 16 channels single-ended and 8 channels differential. The channels are configurable for voltage, current, and current/HART.

Figure 6. HART analog input module IC695ALG626 - RX3i[4]

5.2.1.4. Phoenix Contact/AXL P AI8 HART 1F - Analog module

The analog input I/O module with HART capabilities collects analog input and HART data from the field I/O terminals and makes this information available to the bus coupler through the Axioline P local bus.

Figure 7. Analog output card AXL[5]

5.2.1.5. Schneider Electric/ Modicon X80

The Modicon X80 is a range of I/O (Input/Output) modules and racks produced by Schneider Electric. They are part of the hardware component and provide HART-compatible analog inputs.

Figure 8. HART analog input card BMXAMO0410H[6]

5.2.1.6. ABB | AI845 Analog Input S/R HART 8 ch

The ABB AI845 Analog Input S/R HART 8 ch is a module that's part of the ABB's S800 I/O range. It provides eight analog input channels and supports HART protocol.

Figure 9. Analog Input S/R HART 8 ch AI845 [7]

5.2.2. DCS

One of the key advantages of using DCS for HART devices is the ability to access detailed information about the devices. DCS can read and interpret the digital data transmitted by HART devices, providing valuable insights into their health, status, and diagnostics. This information can be used for predictive maintenance, troubleshooting, and optimizing process performance.

Some examples of DCS modules:

5.2.2.1. Honeywell|C300

The Honeywell C300 Controller is part of Honeywell's Experion LX and Experion PKS distributed Control Systems (DCS). This controller is the core unit for control and data acquisition in these systems, and it's designed to enhance process control performance and reliability.

Figure 10. DCS Honeywell C300[8]

5.2.2.2. Yokogawa|JUXTA D

The D Series is a DCS-supported signal conditioner, consisting of modular type signal converters with versatile I/O specifications and housing nest.

Figure 11. DCS Yokowaga JUXTA D[9]

5.2.2.3. ABB|System 800xA

The System 800xA can be used to communicate with HART-enabled devices. This means that System 800xA can collect, configure, calibrate, and diagnose HART devices. It does this through HART-capable I/O modules, which can communicate with HART devices and bring their data back to the System 800xA.

Figure 12. DCS ABB System 800xA[10]

5.2.2.4. Rockwell automation|PlantPAx

Rockwell Automation's PlantPAx Distributed Control System (DCS) supports the use of HART (Highway Addressable Remote Transducer) protocol through specific I/O modules. These modules can communicate with HART-enabled devices, allowing for enhanced device management and diagnostics.

Figure 13. DCS Rockwell automation PlantPAx[11]

5.2.3. Field Communicator

The HART communicator is ideal for monitoring or calibrating multiple instruments or for monitoring instruments in hazardous areas. The HART communicator does not require physical contact with the instrument, so it can be used in places where physical access is limited or hazardous. It also provides the ability to monitor or calibrate multiple instruments, which can be especially helpful in industrial or hazardous environments.

Figure 14. Yokogawa YHC5150X Portable Hart Communicator(Left)[12] and Emerson AMS Trex Device Communicator (Right) [13]

5.2.4. HART Modem

The HART modem is a signal modulation/demodulation device that exchanges information efficiently over a serial link. It is in compliance with the HART protocol. The HART modem allows users to send and receive data between two devices over a serial link. It is a simple and reliable communication solution and can be used with a variety of devices.

Figure 15. HART modem Commubox FXA195 USB/HART modem [14]

6. Does Rheonics inline viscosity and density meter support HART?

Yes, all Rheonics SME sensor electronics support the HART communication protocol. It can be ordered prior to the shipment or can be enabled remotely. To order the HART communication protocol on Rheonics sensors, check for the C8-HART option on the RFQ page for the specific device you are ordering, eg. inline viscometer SRV or inline density meter SRD. More information on how to order the HART communication protocol can be found in this support article: Getting Started with HART communication

7. How does Rheonics support HART integration and development?

FieldComm Group is an organization that develops standards for communication and integration between devices and systems in the petrochemical industry. They provide specifications, test procedures, and other documentation for digital communication technologies. They also provide training and support services to help companies implement these technologies. HART partnership between FieldComm Group and Rheonics

Figure 16. Rheonics membership in Fieldcomm Group

Rheonics provides detailed user manuals and technical support for integration. Our HART-compatible sensors can be easily integrated into any HART network thanks to all the guidelines and steps provided in our support portal. In addition, our experienced engineering team can assist with installation and configuration to ensure successful integration into your HART network in a timely manner. Visit our Support portal for more information on HART Protocol: HART