The Rosemount 644 temperature transmitter is a standard device that can be used with various types of sensor inputs and can be installed economically and efficiently, with measurement accuracy higher than direct-wired solutions. This transmitter can be configured for top mounting in DIN B style and offers various housing options. To achieve reliable performance in process environments, this device uses a 4 to 20 mA signal that is resistant to noise and compensates for ambient temperature.

here are the key features of the Rosemount 644 Temperature Transmitter—tailored for high-precision, flexible, and safe temperature measurement in industrial applications:

🌡️ Precision & Compatibility

Universal sensor input: Supports RTDs, thermocouples, millivolt, and ohm sensors.

Sensor-transmitter matching: Enhances accuracy using Callendar-Van Dusen constants.

Advanced temperature diagnostics: Detects thermocouple degradation and drift.

🔧 Installation Flexibility

Mounting options: Available in head, field, and rail-mount styles.

Local Operator Interface (LOI): Configure directly in the field—no handheld needed.

📡 Communication Protocols

Multivariable output: Includes sensor type, temperature, diagnostics, and status.

Supports HART®, FOUNDATION™ Fieldbus, and PROFIBUS® PA protocols.

🔐 Safety & Reliability

SIL 2/3 certified: Safe for use in critical safety instrumented systems.

Hot Backup™ capability: Ensures continuous operation if one sensor fails.

🛠️ Maintenance & Integration

Configuration tools: Compatible with AMS Device Manager and other asset management platforms.

Enhanced response time: Supports dynamic compensation in changing process conditions.
 

Specifications

FAQ for the Rosemount 644 Temperature Transmitter, perfect for spec sheets, training materials, or customer-facing documents:

🔍 Frequently Asked Questions – Rosemount 644

1. What types of sensors does the 644 support? 

It supports RTDs (e.g., Pt100, Pt1000), thermocouples (Types J, K, T, etc.), millivolt, and resistance inputs.

2. What communication protocols are available? 

The transmitter is available with HART®, FOUNDATION™ Fieldbus, and PROFIBUS® PA protocols.

3. Can I configure the transmitter in the field? 

Yes, with the Local Operator Interface (LOI), you can configure it without any handheld communicator or software.

4. What is Hot Backup™ and how does it work? 

Hot Backup™ allows dual sensor input—if one sensor fails, the transmitter automatically switches to the backup, ensuring uninterrupted measurement.

5. Is the 644 suitable for safety-critical applications? 

Absolutely. It’s SIL 2/3 certified per IEC 61508, making it ideal for Safety Instrumented Systems (SIS).

6. What is the typical accuracy? 

With matched RTDs, accuracy can be as high as ±0.08 °C.

7. What mounting options are available? 

You can choose from head-mount, field-mount, or rail-mount configurations depending on your installation needs.

8. How is sensor drift or failure detected? 

The transmitter includes diagnostics for sensor drift, thermocouple degradation, and wiring issues.

9. What tools are compatible for configuration and diagnostics? 

It integrates with AMS Device Manager and other asset management systems for remote configuration and monitoring.

10. What’s the ambient operating temperature range? 

It operates reliably from –40 to 85 °C (–40 to 185 °F).