Emerson Rosemount 644 HART, Reference Manual

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Specifications and Reference Data
Specifications and Reference Data
July 2016
Reference Manual
00809-0100-4728, Rev MB
Sensor connections
A.1.4 Conformance to specifications
A Rosemount product not only meets its published specifications,
but most likely exceeds them. Advanced manufacturing
techniques and the use of Statistical Process Control provide
specification conformance to at least ± 3 s
(1) . Our commitment
to continual improvement ensures that product design, reliability,
and performance will improve annually.
For example, the Reference Accuracy distribution for the
Rosemount 644 is shown in
Figure A-1 . Our specification limits are
± 0.15 °C, but, as the shaded area shows, approximately 68 percent
of the units perform three times better than the limits. Therefore,
it is very likely that you will receive a device that performs much
better than our published specifications.
Conversely, a vendor who “grades” product without using process
control, or who is not committed to ± 3 performance, will ship a
higher percentage of units that are barely within advertised
specification limits.
Figure A-1. Typical Accuracy
Accuracy distribution shown is for the Rosemount 644, Pt 100 RTD sensor,
Range 0 to 100 °C
A.2 4–20 mA / HART specifications
A.2.1 Communication requirements
Transmitter power terminals are rated to 42.4 Vdc. A Field
Communicator requires a loop resistance between 250 –
1100 ohms. The Rosemount 644 HART device does not
communicate when power is below 12 Vdc at the transmitter
terminals.
A.2.2 Power supply
An external power supply is required for HART devices. The
transmitter operates on 12.0 to 42.4 Vdc transmitter terminal
voltage with load resistance between 250 and 660 ohms. A
minimum of 17.75 Vdc power supply is required with a load of 250
ohms. Transmitter power terminals are rated to 42.4 Vdc.
Rosemount 644 Sensor Connection Diagram:
Rosemount 644 Head mount
Rosemount 644 Sensor Connection Diagram:
Rosemount 644 Rail mount
* 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.
1. Sigma ( ) is a statistical symbol to designate the standard deviation from
the mean value of a normal distribution.
2-wire
RTD and
V
3-wire RTD
and
V
4-wire RTD
and
V
T/C
and mV
*
1 2 3 4 1 2 3 4 1 2 3 4 1 2 3 4


Maximum Load = 40.8 x (Supply Voltage – 12.0)

Lower
Specification
Limit Upper
Specification
Limit
–3

–2

–1

1

2

3

4–20 mA dc
1322
1100
1000
750
500
250
0
10 12.0 20 30 40 42.4
Supply Voltage (Vdc)
Operating Region