SKU: 3721

Triconex 3721 TMR Analog Input Module

The Triconex 3721 is a 32-point TMR Analog Input Module providing SIL 3 safety for industrial processes. Features Triple Modular Redundancy and 0-5VDC support

Product Overview

The Triconex 3721 stands as a high-density, Triple Modular Redundant (TMR) Analog Input Module designed specifically for the Tricon safety system. This module provides a high level of integrity for critical process variables such as pressure, temperature, and flow. By utilizing three independent input channels, the 3721 ensures that industrial processes remain safe even if a hardware fault occurs. While Schneider Electric (Invensys) officially discontinued this model in 2018, it remains a vital component in existing safety-instrumented systems (SIS) worldwide due to its robust architecture and precision.

Triple Modular Redundancy (TMR) Technology

The 3721 module operates using a sophisticated “voting” mechanism that distinguishes it from standard industrial I/O. As signals enter the module, the following logic ensures maximum reliability:

Threefold Signal Processing: Each of the 32 input points is isolated and routed to three separate sensing sub-circuits.
Hardware Voting: The three internal microprocessors compare the digitized values. If one channel deviates from the others, the system identifies the discrepancy and maintains the correct value based on the majority.
Continuous Self-Diagnostics: The module runs background “force-to-value” tests to detect stuck-at faults or leakage currents without interrupting the actual process signal.

Industrial Versatility and Integration

Engineered for the most demanding environments, the Triconex 3721 provides a DC-coupled interface that supports standard 0–5 VDC or -5 to +5 VDC signals. This flexibility allows it to interface with a wide variety of field transmitters. Furthermore, the module features:

Environmental Resilience: It maintains peak accuracy in extreme conditions, with an operating range spanning from -40°C to +70°C.
Interoperability: It supports communication via MODBUS and other industry-standard protocols through the Tricon main processors, facilitating easy data sharing with DCS and HMI platforms.
Hot-Swappable Design: Maintenance personnel can replace a faulty module while the system is powered and the process is running, ensuring zero downtime.

Safety Compliance and Certification

The 3721 module adheres to the most stringent international standards for functional safety. It is certified for use in Safety Integrity Level 3 (SIL 3) applications, providing the necessary risk reduction for high-hazard industries like petrochemical refining and nuclear power generation. Compliance with UL, CE, and CSA regulations further confirms its suitability for global industrial deployment.