Foxboro DCS Compact FBM241/c/d, Redundant, Discrete I/O Modules

communication over the active path.

Modular Baseplate Mounting

The modules mount on a DIN rail mounted modular baseplate, which accommodates

up to 16 compact FBMs. The baseplate is either DIN rail mounted or rack mounted,

and includes signal connectors for redundant fieldbus, redundant independent DC

power, and termination cables.

Security

Field power for contacts or solid state switches is current limited.

Termination Assemblies

Field I/O signals connect to the FBM subsystem via DIN rail mounted TAs. The TAs

used with the Compact FBM241/c/d are described in Termination Assemblies And

Cables, page 14.

The redundant adapter connects the redundant FBM’s baseplate connectors together.

The redundant adapter provides a single termination connection to a single TA.

Termination Assemblies and Cables

Field I/O signals connect to the FBM subsystem via DIN rail mounted termination

assemblies (TAs). Multiple types of TAs are available with FBMs to provide I/O signal

connections, signal conditioning, optical isolation from signal surges, external power

connections, and/or fusing for protection of the FBM and/or field device as required by

the particular FBM. Since these features are built into the termination assemblies

(where required), in most applications there is no need for additional termination

equipment for field circuit functions such as circuit protection or signal conditioning

(including fusing and power distribution).

The DIN rail mounted termination assemblies connect to the Compact FBM baseplate

by means of removable termination cables. The cables are available in a variety of

lengths, up to 30 meters (98 feet), allowing the termination assemblies to be mounted

as needed by plant design. See Functional Specifications- Termination Assemblies,

page 16 for termination cable part numbers and specifications.

Discrete Inputs

Termination assemblies with discrete inputs support eight 2-wire discrete input signals

at passive low voltage levels of less than 60 VDC and active high voltage levels of

125 VDC, 120 VAC, or 240 VAC. Active termination assemblies support input signal

conditioning for FBMs. To condition signals, these termination assemblies can provide

optical isolation, current limiting, noise reduction, voltage attenuation, or optional

terminal blocks to connect externally supplied excitation voltage.

LowVoltage Discrete Inputs

The low voltage inputs (less than 60 VDC) use passive termination assemblies. Inputs

can either be voltage monitor, switched or contact sense types. Voltage monitor inputs

require an external field voltage source. Contact sense input use the FBM auxiliary

+24 VDCpowersupply to wet field contacts.

Aload may not be required for proper operation of the input channels. A diode may be

required for a DC inductive load only.

High Voltage Discrete Inputs

The high voltage input circuits support 125 VDC, 120 VAC, or 240 VAC. Inputs can be

either voltage monitor or switched types. Voltage monitor inputs require a field voltage

source. Switch inputs use customer supplied excitation voltage applied to dedicated

terminals on the termination assembly and distributed on the termination assembly to

each of the input channels.

These circuits are located on daughter boards that are mounted under the component

covers of the termination assemblies

Discrete Outputs

Termination assemblies with discrete outputs support eight 2-wire discrete output

signals at passive low voltages of less than 60 VDC and active high voltage levels of

120 VACor240VAC.Active termination assemblies support output signal

conditioning for FBMs. To condition signals, these termination assemblies provide

fuse protection, relays, solid-state devices, and terminal blocks to connect externally

supplied optional power distribution.

LowVoltage Discrete Outputs

The low voltage outputs (less than 60 VDC) use passive termination assemblies.

These assemblies are available with and without output protection (fusing).

Termination assemblies with protection have individual user serviceable fuses that are

designed to limit the output current to 2 A. Eight vertically mounted, one per channel,

3.15 A sand filled fuses (temperature derated) allow a maximum of 2 A current per

output channel. Termination assemblies without fusing (unprotected) are intended for

use by Foxboro engineers or customers who are using interposing relays or fuse

terminal blocks between the termination assembly and the field devices.

Power for the low voltage outputs can be supplied by the FBM +24 VDC auxiliary

power supply (internally (FBM) sourced) or by a field voltage