Foxboro FBM237 Output Module

Foxboro FBM237 Output Module

DESCRIPTION

The FBM237, 0 to 20 mA Output Interface Module contains eight channel isolated 0 to 20 mA dc analog output channels. The outputs are galvanically isolated from other channels and ground. The module can be used as a single unit, or as a redundant pair.

Features

• Eight 4 to 20 mA dc analog output channels 

• Each output channel is galvanically isolated 

• Single or redundant modules 

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

• TAs for locally or remotely connecting field wiring to the FBM237 

• 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 

• Electrically compatible with standard HARTsignals

Redundant Analog Outputs

A redundant analog output function block, AOUTR, is used for each redundant pair of outputs. The AOUTR block handles output writes and initialization logic for the redundant channels. On each execution cycle identical output writes are sent to both modules, fully exercising the fieldbus and the logic circuitry of each module. When 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.

Each output channel drives an external load. Transmitter power from each module is diode OR’d together in the redundant adapter to help ensure redundant power. The microprocessor of each module executes the analog output application program, plus security routines that validate the health of the module.

Configurable options in the modules 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 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.

Functional Specifications

Output Load：750 Ω maximum

Output Processing Delay：30 ms maximum

Output Range (each channel)：0 to 20.4 mA dc

Resolution：13 bits

Field Device Cabling Distance：Maximum distance of the field device from the FBM is a function of compliance voltage (18 V dc at 20.4 mA output), wire gauge, and voltage drop at the field device.

Communication：Communication with its associated FCM or FCP via the module fieldbus

Power Requirements：

• Input Voltage Range (Redundant): 24 V dc +5%, -10% 

• Consumption (Maximum): 7 W 

• Heat Dissipation (Maximum): 5 W

Temperature：

• Module: –20 to +70°C (-4 to +158°F) 

• Termination Assembly – PA: -20 to +70°C (-4 to +158°F)

Relative Humidity：5 to 95% (noncondensing)

Altitude：-300 to +3,000 m (-1,000 to +10,000 ft)

Vibration：7.5 m/s2 (5 to 500 Hz)

Contamination：Suitable for use in Class G3 (Harsh) environments as defined in ISA Standard S71.04, based on exposure testing according to EIA Standard 364-65, Class III.