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Specifications and Reference Data
July 2016
Power supply effect
Less than ±0.005% of span per volt
Stability
RTDs and thermocouples have a stability of ±0.15% of output
reading or 0.15 °C (whichever is greater) for 24 months
Self calibration
The analog-to-digital measurement circuitry automatically
self-calibrates for each temperature update by comparing the
dynamic measurement to extremely stable and accurate internal
reference elements.
Vibration effect
The Rosemount 644 is tested to the following specifications with
no effect on performance per IEC 60770-1, 1999:
Frequency
Vibration
10 to 60 Hz
0.21 mm displacement
60 to 2000 Hz
3 g peak acceleration
Sensor connections
Rosemount 644
244EH
1 2 3 4
1 2 3 4
2-wire
3-wire RTD
*
RTD and V
and V
* Emerson Process Management provides 4-wire sensors for all single element
RTDs. You can use these RTDs in 3-wire configurations by leaving the
unneeded leads disconnected and insulated with electrical tape.
Tagging
Hardware
13 characters total
Tags are adhesive labels affixed to the side of the transmitter
Permanently attached to transmitter
Character height is
1
/
-in (1.6 mm)
16
Software
The transmitter can store up to eight characters for the HART
protocol
Order software tag with C1 option code
Specifications and Reference Data
Sensor connections diagram
1 2 3 4
1 2 3 4
4-wire RTD
T/C
and V
and mV
A.6.4 4–20 mA / HART Specifications
Power supply
External power supply required. Transmitters operate on 12.0 to
42.4 Vdc transmitter terminal voltage (with 250 ohm load, 18.1
Vdc power supply voltage is required). Transmitter power
terminals rated to 42.4 Vdc.
Load limitations
Maximum load = 40.8 X (supply voltage - 12.0)
4–20 mA dc
1240
1100
1000
750
500
250
0
10
18.1
30
12.0 Min
Supply Voltage (Vdc)
1.
Without transient protection (optional).
Note
HART Communication requires a loop resistance between
250 and 1100 ohms. Do not communicate with the
transmitter when power is below 12 Vdc at the transmitter
terminals.
Temperature limits
Operating limit
–40 to 185 °F
(1)
With LCD display
–40 to 85 °C
Without LCD
–40 to 185 °F
display
–40 to 85 °C
1.
LCD display may not be readable and display updates will be slower at
temperatures below -4
F (-20
Hardware and software failure mode
The Rosemount 644 features software driven alarm diagnostics
and an independent circuit which is designed to provide backup
alarm output if the microprocessor software fails. The alarm
direction (HI/LO) is user-selectable using the failure mode switch.
If failure occurs, the position of the switch determines the
direction in which the output is driven (HI or LO). The switch feeds
into the digital-to-analog (D/A) converter, which drives the proper
alarm output even if the microprocessor fails. The values at which
the transmitter software drives its output in failure mode depends
on whether it is configured to standard, custom, or
NAMUR-compliant (NAMUR recommendation NE 43, June 1997)
operation.
Table A-1 on page 86
ranges.
Reference Manual
00809-0100-4728, Rev MB
HART and Analog
Operating Range
Analog Only
Operating Range
42.4
Storage limit
–50 to 185 °F
–45 to 85 °C
–60 to 248 °F
–50 to 120 °C
C).
shows the configuration alarm
(1)
99
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