FOXBORO FBM218 HART® Communication Redundant Output Interface Module

FOXBORO  FBM218 HART® Communication Redundant Output Interface Module

DESCRIPTION

The Compact FBM218 module offers redundant modules for eight output channels, each providing a 4 to 20 mA output signal or a digital HART® signal superimposed on a 4 to 20 mA analog output signal.

FEATURES 

Key features of the Compact FBM218 module are:

 Eight channel-isolated output channels, each providing one of the following outputs: 

• Standard 4 to 20 mA analog output signal 

• Digital HART Frequency Shift Keying (FSK) signal superimposed on a 4 to 20 mA analog output signal. 

 Module pair offers redundancy at the FBM level 

 FSK modem dedicated to each output channel for bi-directional digital communications with a HART field device

 Support for HART universal commands necessary to interface the field device with the Foxboro Evo™ system 

 Galvanic isolation of all output channels from each other, from ground, and from module logic 

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

 Termination Assemblies (TAs) for locally or remotely connecting field wiring to the Compact FBM218.

COMPACT DESIGN

The Compact FBM218’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.

HIGH RELIABILITY

The redundancy of the module pair, coupled with the high coverage of faults, provides very high subsystem availability. Either module may be replaced without upsetting field signals to the other module. A module can be removed or replaced without removing field device termination cabling, power, or communications cabling.

REDUNDANT ANALOG OUTPUTS

If a failure is detected in one of the modules, its output is driven to 0 mA and the corresponding channel in the good module automatically continues supplying the proper current to the output current loop.

Each output channel drives an external load and produces a 0 to 20 mA output. Outputs are combined in series through the redundant adapter. The microprocessor of each module executes the analog I/O application program, plus security routines that validate the health of the FBM.

Configurable options in the modules for output security include Fail-Safe Action (Hold/Fallback), Analog Output Fail-Safe Fallback Data (on a per channel basis), Fieldbus Fail-Safe Enable, and Fieldbus Fail-Safe Delay Time. The Analog Output Fail-Safe Fallback Data option must be set for 0 mA output. This removes one of the pair of redundant output channels from service for detectable problems such as a module not properly receiving output writes or not passing security tests on FBM microprocessor writes to output registers. Setting of the Analog Output Fail-Safe Fallback Data option for 0 mA output also minimizes the possibility of a “fail high” result.

EASY REMOVAL/REPLACEMENT

The module mounts on a Compact 200 Series baseplate which is either DIN rail mounted or rack mounted horizontally, and includes signal connectors for redundant fieldbus, redundant independent dc power, and termination cables. Two screws on the FBM secure the module to the Compact 200 Series baseplate.

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 (see Figure 1). A single termination cable connects from the redundant adapter to the associated termination assembly (TA).

FIELDBUS COMMUNICATION

A Fieldbus Communication Module or a Control Processor interfaces the redundant 2 Mbps module Fieldbus used by the FBMs. The Compact FBM218 module accepts communication from either path (A or B) of the redundant 2 Mbps fieldbus – should one path fail or be switched off at the system level, the module continues communication over the active path.