FOXBORO FBM204

Description

The FBM204, 0 to 20 mA Input/Output contains four 20 mA dc analog input channels
and four 20 mA dc analog output channels.
Each input channel accepts an analog sensor input such as a 4 to 20 mA transmitter,
or a self-powered 20 mA source. Each output channel drives an external load and
produces a 0 to 20 mA output. The inputs/outputs are galvanically isolated from other
channels and ground.
The FBM204 performs the signal conversion required to interface the electrical input/
output signals from the field sensors to the optionally redundant fieldbus. The FBM204
executes the Analog I/O application program, which provides the following
configurable options: Conversion Time, Fail-Safe Configuration (Hold/Fallback), and
Analog Output Fail-Safe Fallback Data (on a per channel basis). The Fieldbus Module
(FBM) may instead execute a distributed PIDA (DPIDA) application program to
provide a fast control loop running in it.
The FBM204 is electrically compatible with standard HARTsignals.
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
High Accuracy
For high accuracy, the module incorporates Sigma-Delta data conversion on a per
channel basis, which provides new analog input readings every 25 ms, and a
configurable integration period to remove any process and/or noise and power line
frequencies. Each time period, the FBM converts each analog input to a digital value,
averages these values over the time period and provides the averaged value to the
controller.

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.
Visual Indicators
Red and green light-emitting diodes (LEDs) incorporated into the front of the module
provide visual status indications of FBM functions.
Easy Removal/Replacement
The module mounts on a Compact 200 Series baseplate. Two screws on the FBM fix
the module to the baseplate. The module can be removed/replaced without removing
field device termination cabling, or power or communications cabling.
Fieldbus Communication
A Fieldbus Communications Module or a Control Processor interfaces to the
redundant 2 Mbps module Fieldbus used by the FBMs. The FBM accepts
communication from either path (A or B) of the 2 Mbps Fieldbus. If one path is
unsuccessful or is switched at the system level, the module continues communication
over the active path.
Modular Baseplate Mounting
The module mounts on a DIN rail mounted modular baseplate, which accommodates
up to four or eight FBMs. The modular baseplate is either DIN rail mounted or rack
mounted, and includes signal connectors for redundant Fieldbus, redundant
independent dc power, and termination cables.
Termination Assemblies
Field I/O signals connect to the FBM subsystem via DIN rail mounted TAs. The TAs
used with the FBM204 are described in Termination Assemblies and Cables, page 11.