Foxboro DCS Compact FBM241/c/d, Redundant, Discrete I/O Modules

Foxboro  DCS Compact FBM241/c/d, Redundant, Discrete I/O

Modules

The Compact FBM241. FBM241c, and FBM241deach have eight discrete inputs and

eight discrete outputs available as a single or redundant module. A redundant pair of

the modules combine to provide redundancy at the FBM level with field I/O wired to

one commontermination assembly.

The Compact Channel Isolated, Discrete I/O Interface Modules (Compact FBM241/c/

d) have eight discrete input channels and eight discrete output channels. Associated

termination assemblies (TAs) support discrete input or output signals at voltages of

under 60 VDC, 120 VAC/125 VDC, or 240 VAC.

Depending on the type of I/O signal required, the TAs contain current limiting devices,

fuses, relays, or relay outputs with internal or external power source and fusing.

The module is available in three distinct types and each type with its associated TA

supports the following discrete inputs and outputs:

Each type of Fieldbus Module (FBM), without signal conditioning, uses a 15 to 60

VDCinput or output signal. Each discrete input and output is galvanically isolated

from other channels and ground. When used with external excitation, each discrete

input and output is group isolated.

The module performs signal conversion required to interface electrical input signals

from field sensors to the optionally redundant fieldbus. It executes the Discrete I/O or

Ladder Logic program, with the following configurable options: Input Filter Time, Fail

Safe Configuration, Fail-Safe Fall-Back, and Sustained or Momentary Outputs. If the

Momentary Output configuration is selected, then Pulse Output Interval is also

configurable

Features

• 8discrete inputs

• 8discrete outputs

• Single or Redundant Module

• Supports discrete inputs/output signals at voltages of:

◦ 15to60VDC

◦ 120VAC/125VDC

◦ 240VAC

• Eachinput and output is galvanically isolated: group isolated when used with

external excitation

• Compact,rugged design suitable for enclosure in Class G3 (harsh) environments

• Executes the Discrete I/O or Ladder Logic program, with the following

configurable options: Input Filter Time, Fail Safe Configuration, Fail-Safe Fall

Back, and Sustained or Momentary Outputs

• Various Termination Assemblies (TAs) that contain:

◦ Current limiting devices

◦ Fuses

◦ Relayoutputs

◦ Relayoutputs with internal or external power source and fusing

◦ Solid state outputs

Redundant Outputs

Aredundant contact output function block, COUTR, is used for each redundant pair of

outputs. The COUTR block handles output writes and initialization logic for the

redundant channels. On each write of the COUTR block, identical output writes are

sent to both modules, fully exercising the Fieldbus and the logic circuitry of each

module. You can select a sustained output that follows the block input or a pulsed

output with a selectable pulse width.

Whenafailure is detected in the modules, its output is marked as BAD and the

corresponding channel in the good module automatically continues to drive the

discrete outputs. Each output channel drives an externally powered load. Power for

each Compact FBM241 module is diode OR’d together in the redundant adapter to

help assure redundant power. The microprocessor of each module executes the

digital output application program, plus diagnostic routines that validate the health of

the FBM.

Compact Design

The Compact FBM241’s design is narrower than the standard 200 Series FBMs. It

has a rugged Acrylonitrile Butadiene Styrene (ABS) exterior for physical protection of

the circuits. Enclosures specially designed for mounting the FBMs provide various

levels of environmental protection, up to harsh environments, per ISA Standard

S71.04

Visual Indicators

Light-emitting diodes (LEDs) incorporated into the front of the module provide visual

indication of the Fieldbus Module operational status, as well as the discrete states of

the individual input and output points.

Easy Removal/Replacement

The module mounts on a Compact 200 Series baseplate. Two screws on the FBM

help secure the module to the baseplate.

The module can be removed or replaced without removing field device termination

cabling, power, or communication cabling.

Redundant modules must be located in adjacent positions on the baseplate, with the

first module located in an odd-numbered position (for example, the positions labelled

3 and 4). To achieve redundancy, a redundant adapter module is placed on the two

adjacent baseplate termination cable connectors to provide termination for a single

cable. A single termination cable connects from the redundant adapter to the

associated termination assembly (TA).

Whenredundant, either module can be replaced without upsetting field input signals

to the good module. Each module can be removed or replaced without removing field

termination cabling, power, or communications cabling

Fieldbus Communication

AFieldbus Communications Module or a Control Processor interfaces to the

redundant 2 Mbps module Fieldbus used by the FBMs. The Compact FBM241/c/d

accepts communication from either path (A or B) of the redundant 2 Mbps Fieldbus. If

one path is unsuccessful or is switched at the system level, the module continues