96
Reference Manual
00809-0200-4728, Rev RA
Appendix A: Specifications and Reference Data
April 2015
Specifications and Reference Data
Figure A-3. 644 Sensor Connection Diagram: 644 Fieldbus and PROFIBUS PA Head Mount
and 644 Rail Mount
* Rosemount Inc. 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.
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
(1)
. Our commitment to continual improvement
ensures that product design, reliability, and performance will improve annually.
For example, the Reference Accuracy distribution for the 644 is shown to the right. Our
Specification Limits are ± 0.15 °C, but, as the shaded area shows, approximately 68% of the units
perform three times better than the limits. Therefore, it is very likely 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-4. Typical Accuracy
Accuracy distribution shown is for the 644, Pt 100 RTD sensor, Range 0 to 100 °C.
A.2
4–20 mA / HART specifications
Communication requirements
Transmitter power terminals are rated to 42.4 Vdc. A Field Communicator requires a loop
resistance between 250 – 1100 ohms. The 644 HART device does not communicate when
power is below 12 Vdc at the transmitter terminals.
(1) Sigma (
σ
) is a statistical symbol to designate the standard deviation from the mean value of a normal distribution.
2-wire
RTD and
3-wire RTD
and
4-wire RTD
and
T/C
and mV
*
1 2 3 4
1 2 3 4
1 2 3 4
1 2 3 4
Lower
Specification
Limit
Upper
Specification
Limit
–3
σ
–2
σ
–1
σ
1
σ
2
σ
3
σ
Summary of Contents for Rosemount 644
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