Rosemount 644 Temperature Transmitter Troubleshooting Method

Introduction to Rosemount 644 Temperature Transmitter

644 head mount and rail mount temperature transmitters for high accuracy and reliability for control applications.

The Rosemount 644 Temperature Transmitter is an ideal product for critical applications in a variety of process environments. It provides high-precision measurement for various devices, fully demonstrating the reliability of the product. The Rosemount 644 can be ordered with 4-20mA/HART or the all-digital FOUNDATION fieldbus protocol. Each unit can be configured to accommodate various sensor inputs: RTD, thermocouple, millivoltmeter or ohmmeter.

Powered by digital field devices

The use of HART or fieldbus communication devices ensures high performance and advanced diagnostic technology. From this, these transmitters pass the information to the AMS intelligent device management system.

Transmitter and sensor matching

For intrinsically safe devices, only one safety barrier can input the temperature impedance curve of the specified RTD sensor into the 644 transmitter for several 848T temperature transmitters, and then the transmitter and the sensor can be perfectly matched, avoiding the need for sensors of interchangeability errors, which can improve accuracy by 75%.

Integrated LCD display

Temperature measurement and diagnostics provide immediate and precise changes in process conditions.

Reliable transmitter performance

The 644HART transmitter is NAMURNE21 compliant, which ensures that even in extremely

Best-in-class transmitter performance is maintained in harsh electromagnetic compatibility environments. also,

The 644HART transmitter also complies with NAMURNE43 and NE89 recommendations.

Installation flexibility

Model DINA top junction box mount transmitters are suitable for a variety of remote transmitter mount enclosures and can be integrated or remotely mounted to a single sensor. The compact rail mount type is ideal for DIN rail mounting in tight spaces in dense control rooms.

Rosemount 644 temperature transmitter details:

The Rosemount 644H Temperature Transmitter and Rosemount 644R Smart Temperature Transmitter are extensions of the Rosemount Rosemount Temperature Transmitter family of instruments that accept 2, 3, and 4-wire RTD, thermocouple, and resistance and millivolt inputs . Each transmitter is characterized at the factory for ambient temperature to reduce measurement error over the entire operating temperature range.

The Rosemount 644H Temperature Transmitter can be installed in the connection housing on the sensor to form an integrated temperature assembly, or installed in a junction box away from the sensor; or use the optional installation kit (00644-5301-0010), the The Munters 644H temperature transmitter is mounted on a rail. The Rosemount 644R Temperature Transmitter can be mounted directly on a wall or on a DIN rail.

The Rosemount 644 temperature transmitter has excellent performance and reliability compared with the direct wiring method of the sensor. The optional WAGO spring clip terminal provides an anti-vibration connection method for occasions that do not require fastening, which can greatly reduce wire and labor costs. Advanced Diagnostic features reduce the number of on-site repairs. Order complete temperature transmitter and temperature sensor assemblies to simplify installation, specification and ordering for lower costs. Excellent accuracy, stability and immunity to radio frequency interference, reducing process variability.

Temperature measuring instrument workers often encounter four faults:

Rosemount 644 temperature transmitter does not communicate with the field communicator, 4-20mA output is too high, 4-20mA output is unstable, 4-20mA output is too low or no output. Hiltech summarizes the four faults. Rosemount 644 temperature transmitter troubleshooting method for your reference.

Fault phenomenon 1:

Rosemount 644 Temperature Transmitter Not Communicating with Field Communicator Possible Cause: Problem with loop wiring Troubleshooting:

① Check the version of the 644 temperature transmitter device description information (DD) stored in the communicator. Communicators should report Dev v4, DD v1 (improved) or refer to previous versions of Field Communicator. Please contact the Emerson Process Management Customer Center for assistance.

② Check whether there is at least 250 ohm resistance between the power supply and the Field Communicator connection.

③ Check whether the supply voltage of the Rosemount 644 temperature transmitter is sufficient. If a Field Communicator is connected and the resistance in the loop is 250 ohms, the terminal voltage of the transmitter should be at least 12.0V for operation (over the full 3.5 to 23.0mA operating range) and at least 12.5V for digital communication.

④ Check whether there are intermittent short circuits, open circuits and multiple grounding conditions.

Fault phenomenon 2:

The 4-20mA output of the Rosemount 644 temperature transmitter is too high. 

◆Possible cause 1: The output is too high. The temperature sensor input or connection fails. Troubleshooting:

①Connect the field communicator, and enter the 644 temperature transmitter test mode to check the temperature sensor failure.

② Check whether the temperature sensor is open circuit or short circuit.

③ Check the process variable to see if it is out of range.

◆Possible cause 2: There is a problem with the circuit wiring. Troubleshooting: Check for dirty or defective terminals, interconnect pins, or sockets.

◆Possible reason 3: Power failure Troubleshooting: Check the power output voltage on the Rosemount 644 temperature transmitter terminals. This value should be 12.0 to 42.4Vdc (over the full 3.75 to 23mA operating range).

◆Possible reason 4: There is a fault in the circuit board. Troubleshooting:

①Connect the Field Communicator and enter the Rosemount 644 Temperature Transmitter Status Mode to isolate the module fault.

②Connect the Field Communicator and check the sensor limit value to ensure that the calibration adjustment value is within the sensor range.

Fault phenomenon 3:

Rosemount 644 temperature transmitter 4-20mA output is unstable

◆Possible reason 1: There is a problem with the circuit wiring. Troubleshooting:

① Check whether the supply voltage of the Rosemount 644 temperature transmitter is sufficient. The voltage on the transmitter terminals should be 12.0 to 42.4Vdc (over the full 3.75 to 23mA operating range).

② Check whether there are intermittent short circuits, open circuits and multiple grounding conditions.

③Connect the field communicator and enter the loop test mode to generate 4mA, 20mA signals and user-selected values.

◆Possible cause 2: Circuit board failure Troubleshooting: Connect the field communicator and enter the Rosemount 644 temperature transmitter test mode to isolate the module failure.

Fault phenomenon 4:

Rosemount 644 temperature transmitter 4-20mA output is too low or no output

◆Possible reason 1: The temperature sensor element is faulty. Troubleshooting:

①Connect the Field Communicator and enter the Rosemount 644 Temperature Transmitter Test Mode to isolate the temperature sensor fault.

② Check the process variable to see if it is out of range.

◆Possible reason 2: There is a problem with the circuit wiring. Troubleshooting:

① Check whether the supply voltage of the Rosemount 644 temperature transmitter is sufficient. This value should be 12.0 to 42.4Vdc (over the full 3.75 to 23mA operating range).

② Check whether there is a short circuit and multiple grounding conditions.

③ Check whether the polarity of the signal terminal is correct.

④Check the circuit resistance.

⑤Connect the field communicator and enter the loop test mode.

⑥ Check the wiring insulation to detect whether there is a short circuit to ground.

◆Possible reason 3: Circuit board failure Troubleshooting: Connect the field communicator, and check the sensor limit value to ensure that the calibration adjustment value is within the sensor range.