The Rosemount 644 temperature transmitter is a widely used 2-wire temperature transmitter, primarily known for its stable performance and quality. When ordering the 644 temperature transmitter together with a PT100 thermocouple, optimal performance is achieved.
The Rosemount 644 temperature transmitter is ideal for critical applications (suitable for various process environments). It provides high-precision measurements for a wide range of devices, demonstrating the reliability of Rosemount products. The Rosemount 644 can be ordered with 4-20 mA/HART or fully digital Foundation Fieldbus protocols. Each unit can be configured to accommodate various sensor inputs: RTDs, thermocouples, millivoltmeters, or ohmmeters.
Transmitter and Sensor Matching
For intrinsically safe devices, only one safety barrier is needed for several 848T transmitters. After inputting the temperature impedance curve of the specified RTD sensor into the 644 transmitter, a perfect match between the transmitter and sensor is achieved. This avoids interchangeability errors with the sensor and improves accuracy by 75%.
Installation Flexibility: DIN Type A top junction box mount transmitters are compatible with various remote transmitter housings and can be integrated or remotely mounted to a single sensor. The compact rail mount type is ideal for DIN rail mounting in confined spaces within dense control rooms.
Integrated LCD Display: Local temperature measurement and diagnostic indication functions provide real-time and accurate information on changes in process conditions.
Powered by Digital Field Devices: Utilizing HART or fieldbus communication devices ensures high performance and advanced diagnostic capabilities. These transmitters then transmit information to the Accuracy Management System (AMS).
Reliable Transmitter Performance: The 644 HART transmitter complies with NAMUR NE 21 recommendations, ensuring superior transmitter performance even in extremely demanding electromagnetic compatibility environments. Furthermore, the 644 HART transmitter also complies with NAMUR NE 43 and NE 89 recommendations.
Rosemount temperature transmitters are known for their high stability, especially the 644 model. When purchasing a temperature transmitter, it's crucial to understand its performance to ensure optimal results. How to diagnose abnormalities in a Rosemount 644 temperature transmitter?
The Rosemount 644 temperature transmitter uses thermocouples or resistance temperature detectors (RTDs) as its sensing elements. The signal from the sensing element is sent to the transmitter module, where it undergoes processing including voltage regulation, filtering, operational amplification, nonlinear correction, V/I conversion, constant current, and reverse protection circuitry. This processed signal is then converted into a 4-20mA current signal output that is linearly related to temperature.
Important Notes: The power supply to the Rosemount temperature transmitter must be free of power spikes, as these can easily damage the transmitter. Transmitter calibration should be performed 5 minutes after power-on, taking into account the ambient temperature. When measuring high temperatures (>100℃), the sensor cavity and junction box should be insulated with filler material to prevent the junction box from overheating and burning out the transmitter. When using the sensor in environments with severe interference, the housing should be securely grounded to avoid interference. Power and signal output should be transmitted via Ф10 shielded cable, and the clamping nut should be tightened to ensure airtightness. Only RWB type temperature transmitters have a 0~10mA output, which is a three-wire system. Below 5% of the range, non-linearity occurs due to the transistor's turn-off characteristics. Temperature transmitters should be calibrated every 6 months. If DWB cannot be linearly corrected due to circuit limitations, it is best to select the range according to the instructions to ensure linearity.
Installation Issues: Transmitter No Output
① If the transmitter has no output, check if the transmitter power supply is reversed;
Connect the power supply polarity correctly.
② Measure the transmitter's power supply to ensure there is 24V DC voltage;
The power supply voltage to the transmitter must be ≥12V (i.e., the voltage at the transmitter's power input terminal ≥12V). If there is no power, check for broken circuits, incorrect instrument selection (input impedance should be ≤250Ω), etc.
③ If it's an integrated meter with a built-in meter head, check if the meter head is damaged (you can first short-circuit the two wires of the meter head; if it works normally after short-circuiting, then the meter head is damaged);