Technical Overview

The FOXBORO RH924WA is a high-performance analog input module designed for Schneider Electric’s (formerly Invensys) FOXBORO I/A Series Distributed Control System (DCS), particularly G3 and G4 platforms. It provides 16 independent, galvanically isolated channels for precise acquisition of 4–20 mA signals from field transmitters—making it ideal for monitoring critical process variables such as pressure, temperature, flow, and level in oil refineries, power plants, and chemical facilities. Unlike basic I/O cards, the RH924WA integrates advanced diagnostics, HART digital communication support, and optional redundancy, ensuring data integrity even under electrical noise, thermal stress, or partial hardware failure. Its robust design meets CE, ATEX, and IECEx certifications, enabling safe deployment in Zone 2 hazardous areas.

Real-World Application: Offshore Gas Platform

At a North Sea gas processing platform, the FOXBORO RH924WA modules monitor separator vessel levels and compressor discharge pressures—variables critical to preventing hydrate formation and equipment damage. During a lightning storm that induced a 3 kV transient on field cabling, conventional I/O modules experienced signal saturation. The RH924WA, however, maintained accurate readings thanks to its robust EMI filtering and channel-level isolation. “The HART diagnostics also alerted us to a failing transmitter before it drifted out of spec,” said the platform’s control engineer. Over three years, zero measurement-related trips have been recorded.

Why Redundancy and Diagnostics Matter

In safety-critical loops, a single failed input can trigger unnecessary shutdowns or, worse, mask a developing hazard. The RH924WA mitigates this through:

Per-channel health monitoring: Detects open circuits, short circuits, and signal degradation in real time

Redundant I/O pairing: In 2:1 configurations, two RH924WA modules feed one controller; if one fails, the other takes over seamlessly

HART-enabled asset management: Allows remote calibration and device verification without breaking the loop—critical in hazardous zones

This layered approach aligns with IEC 61511 requirements for diagnostic coverage in Safety Instrumented Functions (SIFs).

Installation & Best Practices

Mount only in FOXBORO-certified I/O carriers (e.g., FBM207 baseplate) with proper grounding (≤1 Ω)

Use twisted-pair, shielded cable for each input; ground shield at controller end only

Enable HART pass-through in FOXBORO Workbench software for seamless device integration

Perform loop validation using built-in test functions—no need for external simulators

Replace modules in matched pairs when used in redundant mode to ensure timing consistency

Complementary Products in FOXBORO Ecosystem

FOXBORO RH914NA: 16-channel analog output module (pairs with RH924WA for closed-loop control)

FBM207 Baseplate: Supports hot-swap and redundant power for RH-series I/O

I/A Series Controllers (CP60. CP80): Execute control logic and manage I/O synchronization

FOXBORO Workbench: Engineering tool for configuration, trending, and HART device management

RH912NA: Digital input module for discrete signal acquisition in safety interlocks

Conclusion

The FOXBORO RH924WA exemplifies how precision measurement and industrial ruggedness converge in modern DCS architectures. By delivering high-density, isolated analog inputs with embedded intelligence and certified safety compliance, it ensures that every process variable is captured accurately—regardless of environmental or electrical challenges. For engineers maintaining continuous operations in oil & gas, power, or chemical plants, the RH924WA is more than an I/O module; it’s a trusted extension of the plant’s sensory nervous system, engineered to perform when it matters most.