Foxboro FBM204 Input Module

Overview

The FBM204 is a versatile analog I/O module equipped with four 20 mA DC analog input channels 

and four 20 mA DC analog output channels, designed to bridge field-level sensor signals and 

industrial control systems. Each input channel of the FBM204 is capable of accepting signals from 4–

20 mA transmitters or self-powered 20 mA sources, while each output channel can drive external 

loads and deliver precise 0–20 mA output signals. Notably, all input and output channels of the 

FBM204 feature galvanic isolation from one another and from ground, ensuring signal integrity and 

protection against electrical interference or cross-channel faults.

Beyond basic signal transmission, the FBM204 handles the necessary signal conversion to interface 

field sensor electrical signals with an optionally redundant fieldbus. The FBM204 runs a dedicated 

Analog I/O application program that supports per-channel configurable parameters, including 

conversion time, fail-safe behavior (either hold or fallback modes), and analog output fail-safe 

fallback data. For enhanced control capabilities, the FBM204 can alternatively execute a distributed 

PIDA (DPIDA) application program, enabling fast, localized control loops to run directly on the 

fieldbus module (FBM) for reduced latency and improved system responsiveness. Additionally, the 

FBM204 is fully electrically compatible with standard HART signals, supporting seamless integration 

with HART-enabled field devices for advanced diagnostics and configuration.

Features

Four 20 mA DC analog input channels

• Four 20 mA DC analog output channels

• Each input and output channel is galvanically isolated

• Rugged design suitable for enclosure in Class G3 (harsh) environments

• Execution of an analog I/O application program that provides conversion time and configurable 

options for Rate of Change Limits

• High accuracy achieved by sigma-delta data conversions for each channel

• Termination Assemblies (TAs) for locally or remotely connecting field wiring to the Compact FBM204

• TA for use with Output Bypass Station to maintain outputs during maintenance operations

• 3-tier termination assembly for per channel internally and/or externally loop powered transmitters

• Support for DPIDA control blocks

Standard Design

FBM204 has a rugged extruded aluminum 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.

Functional Specifications

Environmental Specifications

Physical Specifications