Emerson Rosemount 644 Reference Manual

Emerson Rosemount 644

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Reference Manual

00809-0200-4728, Rev RA

April 2015

Rosemount 644 Temperature Transmitter

with HART

®

Protocol

Table of Contents

Other manuals for Emerson Rosemount 644

Quick Start Guide52 pages

Questions and Answers:

R
Randy StoneAug 7, 2025
How to troubleshoot an Emerson Transmitter that does not communicate with Field Communicator?
- C
  christopher28Aug 7, 2025
  If your Emerson Transmitter isn't communicating with the Field Communicator, start by checking the loop wiring. Ensure there's a minimum of 250 ohms resistance between the power supply and Field Communicator connection. Also, verify that the transmitter is receiving adequate voltage; it needs a minimum of 12.0 V at the terminals to operate across the 3.5 to 23.0 mA range and at least 12.5 V to communicate digitally. Finally, inspect the wiring for intermittent shorts, open circuits, and multiple grounds.
C
Charles McintoshAug 14, 2025
What to do if Emerson Rosemount 644 Transmitter has low or no output?
- A
  aschneiderAug 14, 2025
  If your Emerson Transmitter shows low or no output, begin by checking the loop wiring for adequate voltage, ensuring it's between 12.0 to 42.4 Vdc across the 3.75 to 23 mA operating range. Also, check for shorts and multiple grounds, verify proper polarity at the signal terminal, and inspect the loop impedance. Examine the wire insulation for potential shorts to ground. You may also want to check if the process variable is out of range. To isolate a sensor failure, use a Field Communicator and enter the transmitter test mode. Also, use a Field Communicator to check the sensor limits and ensure calibration adjustments are within the sensor range.
C
Cynthia CarterAug 21, 2025
Why is my Emerson Transmitter showing a high output?
- S
  smithtanyaAug 21, 2025
  If your Emerson Transmitter is showing high output, start by checking the process variable to see if it is out of range. Inspect the loop wiring for dirty or defective terminals, interconnecting pins, or receptacles. Verify the power supply output voltage at the transmitter terminals, ensuring it's between 12.0 to 42.4 Vdc across the 3.75 to 23 mA operating range. To check for a sensor failure, connect a Field Communicator and enter the transmitter test mode. Also, check for a sensor open or short circuit. To isolate module failure, connect a Field Communicator and enter the transmitter status mode. Finally, connect a Field Communicator and check the sensor limits to ensure calibration adjustments are within the sensor range.
C
Christopher DavisAug 29, 2025
How to fix erratic output on Emerson Rosemount 644 Transmitter?
- D
  David DiazAug 29, 2025
  If your Emerson Transmitter is showing erratic output, check the loop wiring. Ensure adequate voltage to the transmitter, which should be 12.0 to 42.4 Vdc at the transmitter terminals across the 3.75 to 23 mA operating range. Also, check for intermittent shorts, open circuits, and multiple grounds. To isolate module failure, connect a Field Communicator and enter the transmitter test mode.

Emerson Rosemount 644 Specifications

General

Type	Temperature Transmitter
Measurement Type	Temperature
Operating/Ambient Temperature	-40 to 85 °C (-40 to 185 °F)
Housing Material	Aluminum or Stainless Steel
Display	Optional LCD
Output Signal	4-20 mA HART
Process Connection	1/2" NPT
Communication Protocol	HART
Enclosure Rating	IP66
Measurement Range	Depends on sensor type

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