Emerson 644 manual Foundation Fieldbus Specifications, Function Blocks, 2 σ -1 σ

Rosemount 644

Reference Manual

00809-0400-4728, Rev AA June 2011

Rosemount 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 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.

Typical Accuracy

Lower	Upper
Specification	Specification
Limit	Limit
–3σ–2σ–1σ	1σ 2σ 3σ

Accuracy distribution shown is for the 644, Pt 100 RTD sensor, Range 0 to 100 °C

3144-GRAPH

(1) Sigma (σ) is a statistical symbol to designate the standard deviation from the mean value of a normal distribution.

FOUNDATION FIELDBUS SPECIFICATIONS

Function Blocks

Resource Block

•The resource block contains physical transmitter information including available memory, manufacture identification, device type, software tag, and unique identification.

Transducer Block

•The transducer block contains the actual temperature measurement data, including sensor 1 and terminal temperature. It includes information about sensor type and configuration, engineering units, linearization, reranging, damping, temperature correction, and diagnostics.

LCD Block

•The LCD block is used to configure the local display, if an LCD Display is being used.

Analog Input (AI)

•Processes the measurement and makes it available on the fieldbus segment.

•Allows filtering, alarming, and engineering unit changes.

PID Block

•The transmitter provides control functionality with one PID function block in the transmitter. The PID block can be used to perform single loop, cascade, or feedforward control in the field.

Instantiable Function Blocks

•All the function blocks used by the transmitter are instantiable, meaning the total number of function blocks is only limited by the physical memory available in the transmitter. Since only the instantiable blocks can use physical memory, any combination of function blocks can be used at any given time as long as the physical memory size is not violated.

Block	Execution Time (milliseconds)
Resource	–
Transducer	–
LCD Block	–
Analog Input 1	45
Analog Input 2	45
PID 1	60

A-4