ABB TB82PH Instruções de Operação descarregar pdf (Página 23)

I-E67-TB82FF-2A February 13, 2002

DEVICE BLOCKS

All variables and parameters of the transmitter are

structured in blocks with respect to their assignment

of components or functions. This structure is termed

the Function Block Application Process (FBAP) and

has been designed to support five primary operational

characteristics:

1. Configuration and definition of function

blocks

2. Configuration of function block links

3. Alert processing

4. Access to information for operator interface,

remote operation, diagnostics, and

configuration

5. Coordinating function block execution and

communication

The basic elements of the FBAP are as follows:

• Block Objects and Parameters

− Resource Block

− Transducer Block

− Function Block (e.g., Analog Input,

Analog Output, PID, etc.)

• Link Objects: Allows the transfer of data

between blocks as defined by the Virtual

Communication Relationship (VCR).

• Alert Objects: Used to communicate alerts

and/or events to other devices.

• Trend Objects: Used to maintain a history of

values of an individual parameter.

• View Objects: Used to group a subset of

operation and configuration data.

• Domain and Program Invocation Objects:

Used to support download and upload

services.

Blocks are logical groups of device functionality that

define a particular application using a common model.

In general, blocks process input parameters and

events through one or more process algorithms and

execution controls in order to produce the expected

output parameters and events. Block parameters

control the function and execution of the block and

are visible over the fieldbus network. Data

communicated over the fieldbus is expressed as an

"object description". Object descriptions are collected

together in a structure called an Object Dictionary

(OD) and are identified within the OD by their index.

During system operation, block parameters are

accessed using an OD index.

Since most plants have many different process

control requirements, the type of functions can greatly

vary. The Fieldbus Foundation specifications identify

a range of function blocks, each addressing a

different need. These standard function blocks

provide a common structure for defining block inputs,

outputs, control parameters, events, alarms, and

modes. This common structure can then be easily

used in a wide range of process control and

monitoring devices.

The Resource Block contains the hardware specific

characteristics associated with a device. This block

does not have input and output parameters; instead, it

contains an algorithm that monitors and controls the

general operation of the physical device hardware.

For example, the mode of the Resource Block

impacts all of the other blocks. Other Resource Block

parameters include but are not limited to the

manufacturer's name, device name, and serial

number. Only one resource block is included per

device.

The Transducer Blocks connect input and output

functions to other function blocks residing in the same

device. It interfaces with sensor input hardware and

provides a measured value and status to connected

function blocks. Transducer Block parameters

include but are not limited to sensor type, temperature

sensor type, calibration data and routines, calibration

date and diagnostic conditions. Usually only one

Transducer Block is present per device.

The Function Blocks are fundamental for providing

the control system behavior. Function Blocks contain

input and output parameters and algorithms and can

be linked to other function blocks within the same

device or to other devices in the fieldbus network. In a

single User Application, several function blocks can

be available and precisely scheduled in terms of

execution.

The Fieldbus Foundation specifications have defined

a set of standard function blocks. These are as

follows:

• Analog Input (AI)

• Analog Output (AO)

• Discrete Input (DI)

• Discrete Output (DO)

• Proportional/Derivative (PD)

• Proportional/Integral/Derivative (PID)

• Bias (B)

• Control Selector (CS)

• Manual Loader (ML)

• Ratio (RA)

The TB82EC FF Transmitter has one Resource

Block, two Analog Input Function Blocks (AI), and one

enhanced, custom Transducer Block with calibration

capability. The following figure shows block elements

for the TB82EC FF Transmitter.

1 2 ... 18 19 20 21 22 23 24 25 26 27 28 ... 59 60

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