Description

The Honeywell FX-USI-0002 is a Universal Serial Interface (USI) module designed for the Experion® FX distributed control system (DCS)—a scalable, high-performance automation platform widely used in oil & gas, refining, chemicals, power, and water treatment. This compact, DIN rail-mounted I/O module enables the Experion FX controller to communicate directly with third-party field devices, legacy systems, and intelligent instruments that utilize serial communication protocols, most notably Modbus RTU, but also supporting ASCII-based or proprietary serial formats via configuration.

As part of Honeywell’s modular I/O architecture, the FX-USI-0002 installs into standard Experion FX I/O carriers (such as the FIM or FBM backplanes) and connects via a high-speed internal bus to the Field Control Station (FCS). It features dual isolated serial ports—typically configurable as RS-485 (for multi-drop networks) or RS-232 (point-to-point)—allowing a single module to interface with multiple devices like flow computers, variable frequency drives (VFDs), analyzers, weigh scales, or older PLCs. The module supports baud rates up to 115.2 kbps and includes robust electrical isolation (typically 500 VAC) to protect the control system from ground loops and transient surges common in industrial environments.

Critically, the FX-USI-0002 reduces engineering complexity by eliminating the need for external protocol converters or gateway hardware. Configuration is performed within Experion PKS Studio or Control Builder, where users define data maps, polling intervals, and fault-handling logic—ensuring seamless integration into control strategies and alarm management. Its hot-swappable design (in redundant configurations) and built-in diagnostics make it ideal for continuous-process applications where uptime is non-negotiable.

Technical Specifications

Main Features and Advantages

Seamless legacy integration without external gateways: The FX-USI-0002 eliminates costly and failure-prone external protocol converters by embedding serial communication directly into the Experion FX I/O layer. This reduces panel space, wiring complexity, and points of failure—while keeping all data within the native Experion environment for unified alarming, trending, and security.

Dual-port flexibility for diverse field devices: With two independently configurable ports, a single FX-USI-0002 can simultaneously poll a Modbus RTU flow computer on Port 1 while exchanging ASCII commands with a legacy analyzer on Port 2. Each port supports different baud rates and protocols, enabling maximum connectivity from minimal hardware.

Robust industrial design for mission-critical processes: The module’s reinforced isolation, conformal coating options (on select variants), and compliance with industrial EMC standards ensure reliable operation in electrically noisy plants—such as near large motors, switchgear, or radio transmitters. Its solid-state design has no moving parts, ensuring long service life.

Native integration with Experion PKS ecosystem: Unlike generic serial servers, the FX-USI-0002 appears as a native I/O tag source in Experion. Engineers can bind serial data directly to control logic, HMI graphics, or historian points—without OPC tunneling or middleware. Built-in redundancy support (when used in dual FCS setups) ensures continuous communication even during controller switchover.

Application Field

The FX-USI-0002 is extensively used in refineries to integrate custody-transfer flow computers (e.g., Daniel, Emerson ROC) into Experion FX batch and blending systems. In natural gas processing plants, it connects to sulfur recovery unit (SRU) analyzers and compressor PLCs using Modbus RTU over long RS-485 runs.

In power generation, the module interfaces with excitation systems, battery monitors, and auxiliary boiler controls that lack modern Ethernet interfaces. Water and wastewater facilities use it to gather data from ultrasonic level sensors, chlorine dosing controllers, and SCADA RTUs operating on legacy serial links.

Chemical plants leverage the FX-USI-0002 for reactor temperature profiling via serial-connected thermocouple scanners, while pharmaceutical manufacturers use it to log data from standalone environmental monitoring systems into the central Experion historian—supporting 21 CFR Part 11 compliance. Across all sectors, the FX-USI-0002 acts as the critical bridge between modern DCS intelligence and the vast installed base of serial-enabled field equipment.

Related Products

• FBM242: Experion FX I/O baseplate/carrier compatible with FX-USI-0002

• FIM (Fieldbus Interface Module): Backplane assembly that houses USI and other I/O modules

• FX-PCI-0001: PCI-based communication module for host-level integration (different layer)

• FX-DI-0008 / FX-AI-0004: Digital and analog I/O modules for same I/O rack

• Experion PKS R510/R520: Controller platforms that utilize FX-USI-0002

• Honeywell Serial Device Integration (SDI) Toolkit: Software add-on for advanced protocol scripting

• TB-FX-USI: Terminal block adapter kit for field wiring

Installation and Maintenance

Pre-installation preparation:

• Confirm your Experion FX I/O carrier (e.g., FBM242) has an available slot and compatible firmware.

• Plan serial cabling using shielded twisted-pair (STP) cable; ground shield at one end only to avoid ground loops.

• For RS-485, ensure proper termination (120 Ω resistor) at the farthest device.

• Configure communication parameters (baud rate, parity, etc.) in Control Builder before powering up.

Maintenance recommendations:

• Monitor the Fault LED—solid red indicates configuration error or communication timeout.

• Use Experion’s diagnostic tools to view port statistics, error counters, and last received data.

• Periodically verify wiring integrity, especially in high-vibration areas.

• Keep firmware updated to benefit from protocol enhancements and bug fixes.

• Store spares in ESD-safe packaging; the module contains sensitive CMOS circuitry.