Rosemount 644RAI5Q4RK Transmitter | 4-Wire RTD, 4-20mA HART, Dual Input, 1/2" NPT

Rosemount 644RAI5Q4RK Transmitter | 4-Wire RTD, 4-20mA HART, Dual Input, 1/2" NPT

Rosemount 644RAI5Q4RK temperature transmitter specifications. Dual RTD input, 4-20mA with HART, 2-wire, 1/2" NPT, 4-20mA output, hazardous area approvals. Part of Rosemount 644 series.

Product Overview

The Rosemount 644RAI5Q4RK​ is a dual-input, 2-wire temperature transmitter​ from Emerson's Rosemount 644 Series. It is configured to accept two 4-wire RTD inputs, provides a single 4-20mA analog output proportional to temperature, and incorporates the HART communication protocol​ for configuration and diagnostics. The transmitter is designed for head or rail mounting and is suitable for a wide range of temperature measurement applications in industrial environments, including hazardous areas.

Model Number Decoding (644RAI5Q4RK)

Technical Specifications

Note: Specifications are based on the Rosemount 644 Series data sheets. Always verify with the latest product manual.

Key Features

• Dual RTD Input:​ Measures two temperatures with a single transmitter, reducing installation cost.

• 4-Wire RTD Measurement:​ Provides highest accuracy by eliminating lead wire resistance error.

• HART Communication:​ Enables remote configuration, calibration, and diagnostics via any HART communicator or host system.

• Wide Power Supply Range:​ 10.5-42.4V DC allows flexible power supply choices.

• Robust Construction:​ Aluminum housing with IP66 rating for harsh environments.

• Flexible Mounting:​ Head-mount (2" pipe) or rail-mount options.

• Advanced Diagnostics:​ Sensor break detection, loop integrity, and process variable limits.

• Global Approvals:​ Certified for use in hazardous areas (ATEX, IECEx, FM, CSA).

• SIL Capable:​ Suitable for Safety Instrumented Systems (SIL 2/3).

Input Configuration and Calculation

The transmitter can be programmed to output a 4-20mA signal based on various functions of the two RTD inputs (T1, T2):

The exact scaling (LRV and URV) is fully programmable via HART.

Wiring Diagram (Typical 4-Wire RTD)

[Power Supply 24V DC +] --------+
                                          |
                                      [Load, e.g., 250Ω]
                                          |
                                          |
    Transmitter 644RAI5Q4RK               |
    Terminal Block:                      |
    Vdc+ (1) ---- Loop+ -----------------+
    Vdc- (2) ---- Loop- ------------------+
    RTD1: I+ (3) ------------------------A RTD1
           I- (4) ------------------------B RTD1
           V+ (5) ------------------------a RTD1
           V- (6) ------------------------b RTD1
    RTD2: I+ (7) ------------------------A RTD2
           I- (8) ------------------------B RTD2
           V+ (9) ------------------------a RTD2
           V- (10) -----------------------b RTD2

Terminals 11 & 12: Common/Shield connection for both RTDs.

Configuration and DTM/DD

Hazardous Area Approvals (Typical)

Note: Specific temperature code (T4/T6) depends on ambient rating. Verify the certificate for the exact code.

Typical Applications

• Motor/Bearing Temperature Monitoring:​ Average or differential temperature of two windings or bearings.

• Heat Exchanger Monitoring:​ Temperature difference across a heat exchanger (ΔT).

• Redundant Temperature Measurement:​ High-select or low-select of two sensors for critical processes.

• Vessel Temperature Profiles:​ Average temperature in a large vessel using two sensors.

• Compressor/ Turbine Monitoring:​ Multiple point temperature monitoring with one transmitter.

• Any application​ requiring two RTD inputs for calculation (average, difference, select) and a single 4-20mA output.

Important Technical Notes

1. Dual Input Logic:​ The transmitter does not output two separate 4-20mA signals. It outputs one​ 4-20mA signal based on a user-defined function​ (Average, Difference, Select, Single) of the two RTD inputs.

2. Sensor Matching:​ For best results, use two RTDs of the same type (e.g., both Pt100) and similar characteristics.

3. Configuration is Mandatory:​ The transmitter must be configured (LRV, URV, input function, RTD type) before use. It does not work "out of the box."

4. Wiring:​ 4-wire RTD connection is required for specified accuracy. 3-wire or 2-wire RTDs can be connected but with reduced accuracy (lead resistance error).

5. HART Communication:​ A 250Ω resistor (minimum) is required somewhere in the 4-20mA loop for HART communication to work.

6. Power Supply:​ Ensure the loop voltage is sufficient to drive the transmitter (min 10.5V) plus the voltage drop across the load resistor at 20mA. V_supply > 10.5V + (0.020A * R_load).

7. Hazardous Area Installation:​ When installed in a hazardous area, follow the entity parameters and installation guidelines in the safety manual. Intrinsic safety barriers or isolators are required.

8. Calibration:​ RTD sensors are primary elements. Transmitter calibration typically involves a sensor trim (using a precision resistance source) or a full trim with a temperature standard.

Note: This data sheet provides general specifications for the Rosemount 644RAI5Q4RK temperature transmitter. For complete installation guidelines, wiring diagrams, configuration procedures, safety manuals, and SIL documentation, consult the official Rosemount 644 Reference Manual​ and the product data sheet. Configuration via a HART communicator is required for operation.