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.