How to Set Up the HART Dynamic Variable Function

Setup In Transmitters and DCS Logic

The HART Dynamic Variable Function is a game-changer for integrating multiple process variables into a Distributed Control System (DCS). This functionality enables a single HART-enabled transmitter to send multiple measured variables (e.g., primary, secondary, tertiary, and quaternary variables) digitally alongside the traditional 4-20 mA signal. Setting up this functionality in your transmitter and DCS ensures streamlined data flow, improved process visibility, and operational efficiency.

This guide walks you through configuring the HART Dynamic Variable Function in transmitters, integrating it into DCS logic, and optimizing the setup for your application.

Step 1: Preparing the Transmitter for HART Communication

1.1 Confirm HART Capability

• Ensure your transmitter supports the HART protocol and is capable of communicating multiple dynamic variables. Examples include Emerson Rosemount transmitters, Honeywell SmartLine transmitters, and ABB 266 series.
• Verify the HART version supported (e.g., HART 5, 6, or 7).

1.2 Configure the Transmitter

1. Connect Using a HART Communicator or PC Software:
   • Use a HART communicator (e.g., Emerson 475) or a PC-based tool like AMS Device Manager or Honeywell Field Device Manager.
   • Connect to the transmitter through the HART communication terminals or over a 4-20 mA loop.
2. Access the Dynamic Variables Settings:
   • Navigate to the transmitter’s configuration menu to assign variables to specific slots:
     • Primary Variable (PV): Typically the main process variable, such as flow or pressure.
     • Secondary Variable (SV): Related data, such as temperature or density.
     • Tertiary Variable (TV): Additional measurement or diagnostic parameter.
     • Quaternary Variable (QV): Another useful value or diagnostic output.
3. Set the Update Rate:
   • Configure how often the transmitter sends updates for the dynamic variables. A faster update rate ensures real-time accuracy but may increase communication load.
4. Enable HART Multivariable Communication:
   • Ensure that the transmitter is set to operate in multivariable mode, allowing the DCS to poll for additional variables beyond the PV.

1.3 Verify Configuration

• Run a diagnostic test to confirm that the transmitter communicates all assigned variables correctly.
• Test the communication loop with a HART communicator to verify signal integrity and data accuracy.

Step 2: Configuring the DCS for HART Integration

2.1 Check DCS Compatibility

• Ensure your DCS supports HART communication and can read dynamic variables. Leading DCS platforms like Emerson DeltaV, Honeywell Experion PKS, ABB 800xA, and Siemens PCS 7 offer native HART support.

2.2 Import the Transmitter Configuration

1. Use the HART device descriptor (DD) or device type manager (DTM) file provided by the transmitter manufacturer.
2. Import the DD/DTM into the DCS to enable seamless integration and parameter mapping.

2.3 Map the Variables

• Assign the dynamic variables (PV, SV, TV, QV) to specific tags or points in the DCS:
  • PV: Configure as the primary control signal for process operations.
  • SV, TV, QV: Display on operator interfaces or use for advanced control and diagnostics.

2.4 Configure Polling Frequency

• Set the DCS polling frequency to balance real-time updates and network efficiency. Typical polling intervals range from 1 to 5 seconds for dynamic variables.

2.5 Develop Logic for Dynamic Variables

• Use the DCS’s logic editor to build control strategies that incorporate dynamic variables:
  • Example 1: Use the PV (flow rate) for control loops and the SV (temperature) for alarms.
  • Example 2: Monitor the TV (density) to adjust pump speed for variable fluid characteristics.

Step 3: Testing and Validation

3.1 Loop Test

• Perform a loop test to ensure the transmitter communicates all variables to the DCS correctly.
• Verify the accuracy of displayed data for PV, SV, TV, and QV.

3.2 Simulate Process Conditions

• Simulate different operating conditions (e.g., flow rate changes, temperature variations) to validate that the DCS logic reacts appropriately to dynamic variables.

3.3 Check Alarms and Diagnostics

• Test alarm settings based on dynamic variables to ensure proper notification and response during abnormal conditions.
• Verify that diagnostics (e.g., sensor health or maintenance alerts) appear correctly in the DCS.

Step 4: Optimizing the Setup

4.1 Enable Advanced Diagnostics

• Many HART transmitters provide detailed diagnostics, such as calibration status or device health. Configure the DCS to display these diagnostics for proactive maintenance.

4.2 Utilize Historical Data

• Store dynamic variable data in the DCS historian to analyze trends and optimize processes.

4.3 Train Operators

• Educate operators on interpreting and using dynamic variable data for better decision-making.

Main Players Providing HART Dynamic Variable Functionality

This table highlights each manufacturer’s HART-enabled product offerings and the software or tools they provide to support integration and configuration in industrial automation systems.

Conclusion

Setting up the HART Dynamic Variable Function in transmitters and integrating it into DCS logic unlocks the full potential of industrial automation. By allowing multiple process variables to be communicated digitally, this feature streamlines system design, improves process visibility, and enables advanced diagnostics.

Whether you’re configuring a new system or upgrading an existing one, following this step-by-step guide will help you maximize the benefits of HART communication. With support from industry leaders like Emerson, Honeywell, and ABB, you can build a robust and efficient setup that enhances operational performance and reliability.