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 that make it a favorite in precision-driven industries:

Multi-Protocol Support: Compatible with HART®, FOUNDATION™ Fieldbus, and PROFIBUS® PA for seamless integration.

Mounting Options: Head, field, and rail-mount styles with various enclosure types for installation flexibility.

Versatile Input Compatibility: Accepts RTD, thermocouple, millivolt, and ohm inputs, including dual sensor configurations.

Advanced Diagnostics: Includes Hot Backup™, sensor drift detection, thermocouple degradation alerts, and enhanced sensor failure indication.

Transmitter-Sensor Matching: Improves accuracy when used with matched RTDs—ideal for critical measurements.

Local Operator Interface (LOI): Enables in-field configuration without the need for handheld communicators.

High Accuracy and Stability: Precise measurements with a long-term stability rating of 0.05% of span for 5 years.

SIL 2/3 Certification: Compliant with IEC 61508 standards for use in safety-instrumented systems.

Customizable Alarming and Output: Supports upscale/downscale failure modes and customized output settings.
 

Specifications

Frequently Asked Questions – Rosemount 644

1. What types of sensors can the 644 accept? 

It supports RTDs, thermocouples (T/Cs), ohm, and millivolt (mV) inputs—single or dual sensor configurations.

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 a handheld communicator or laptop.

4. What is Hot Backup™? 

Hot Backup™ allows seamless switching to a secondary sensor if the primary fails—ideal for critical applications.

5. Is the 644 suitable for safety systems? 

Absolutely. It’s SIL 2/3 certified per IEC 61508, making it suitable for safety-instrumented systems.

6. What’s the power supply requirement?

HART: 11–42.4 VDC

Fieldbus/PROFIBUS: 9–32 VDC

7. How accurate is the transmitter? 

With sensor matching, it can achieve accuracy up to ±0.035°C.

8. What mounting options are available? 

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

9. What diagnostics are included? 

It offers sensor drift detection, thermocouple degradation alerts, and sensor failure indication.

10. Can I use it in harsh environments? 

Yes, it’s rated for NEMA 4X and IP66/67 enclosures and operates from −50 to 85°C.