Description
Core Product Summary
The Foxboro FBMSSW is a specialized servo control fieldbus module engineered for the Foxboro I/A Series Distributed Control System (DCS). Unlike standard general-purpose analog input or output cards, the FBMSSW is designed specifically to handle closed-loop hydraulic or pneumatic actuator positioning by combining LVDT (Linear Variable Differential Transformer) signal conditioning and dedicated servo valve drive control into a single integrated interface.
The module processes raw position feedback signals from mechanical valve links while supplying precise current outputs to drive servo valves. It communicates process variables and control states across the system fieldbus network, enabling high-accuracy positioning for critical industrial final control elements such as steam turbine steam chests, fuel gas valves, and heavy-duty positioning dampers.
Key Technical Specifications
| Specification Parameter | Verified Value / Detail |
| Product Type | Specialized LVDT Servo Control Fieldbus Module |
| System Family | Foxboro I/A Series DCS |
| Primary Application | Hydraulic and pneumatic servo actuator control |
| Feedback Interface | LVDT position feedback processing |
| Control Output | \pm 21 mA servo valve output |
| Auxiliary Supply | \pm 15 V DC auxiliary supply capability |
| System Communication | Foxboro I/A Series Fieldbus architecture |
Detailed Product Overview
The Foxboro FBMSSW serves as a dedicated application card where precise, high-speed mechanical positioning is required. In many process plants, standard 4–20 mA analog output cards lack the dynamic response and specialized feedback loops needed to command hydraulic servo-actuators accurately. The FBMSSW bridges this gap by providing internal excitation for LVDT sensors, demodulating position feedback locally, and executing closed-loop positioning algorithms alongside the fieldbus network.
Because this module directly influences high-energy hydraulic and mechanical final control elements, replacement and integration require strict documentation of existing calibration parameters, zero/span settings, and LVDT wiring configurations. Proper shield grounding and signal isolation are critical to prevent electrical noise from corrupting delicate sensor feedback loops in heavy industrial environments.
System Compatibility & Integration Requirements
| Item / Dependency | Verified Compatibility or Requirement | Practical Note |
| Control System Platform | Foxboro I/A Series DCS | Requires base hardware and system software supporting specialized control modules. |
| Actuator Infrastructure | Hydraulic or pneumatic servo actuators equipped with LVDT feedback | Tailored specifically for valves and mechanisms requiring continuous position feedback. |
| Field Wiring & Shielding | Dedicated multi-conductor cabling with continuous shield grounding | Essential for maintaining signal integrity on low-level LVDT feedback inputs. |
| Power Requirements | Standard system base power feeds combined with internal module requirements | Verify auxiliary voltage requirements (\pm 15 V DC) for connected sensor loops. |
FBMSSW
FBMSSW
Dimensions, Mounting & Connection Notes
- Form Factor: Modular plug-in card designed to fit standard Foxboro I/A Series baseplate slots.
- Field Terminations: Routes signals through dedicated Termination Assemblies (TAs) configured for multi-wire LVDT feedback and servo valve current loops.
- Handling Precautions: Contains static-sensitive electronic components; standard ESD grounding wrist straps must be used during installation or removal.
- Operational Safety Note: Because the FBMSSW controls live mechanical actuators, ensure the controlled loop is placed in manual or a safe locked state before extracting or replacing the module.
FAQ
What is the primary function of the Foxboro FBMSSW?
The Foxboro FBMSSW is a specialized servo control module used to drive hydraulic or pneumatic servo valves while processing LVDT position feedback in Foxboro I/A Series systems.
Can the FBMSSW be used as a standard 4-20 mA analog output module?
No. Unlike standard output cards (such as the FBM237), the FBMSSW includes dedicated LVDT signal conditioning excitation and feedback circuitry built specifically for closed-loop valve positioning.
What type of sensor feedback does the module accept?
It is designed to accept position feedback signals directly from Linear Variable Differential Transformers (LVDTs) linked to industrial valves and actuators.
What precautions should be taken when replacing an FBMSSW module?
Because the module controls active mechanical positioning, operations personnel must coordinate to place the loop in a safe state, record existing calibration and span values, and verify correct LVDT wiring polarity prior to powering the replacement unit.
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