Product Overview

The 3805E is a high-integrity Analog Output Module designed for the Triconex Triple Modular Redundancy (TMR) safety system. It provides eight channels of high-precision 4-20 mA signals to drive final control elements such as control valves, dampers, and speed governors. Utilizing the signature pea-green color code of the Triconex line, the 3805E features three independent internal output legs that are voted at the hardware level. This ensures that even if a single component or "leg" fails, the output signal remains stable and accurate, with a typical switch-over time of less than 10 ms. This module is essential for safety-critical loops in Power Generation, Chemical Processing, and Emergency Shutdown (ESD) systems.

Technical Configuration

The 3805E is engineered for continuous operation and fault-tolerant performance:

• TMR Architecture: Internal voting circuitry combines three independent results to produce a single high-availability output. A failure in one of the three internal channels does not interrupt the process signal.

• Precision Output: Features 12-bit resolution with a high accuracy rating of less than 0.25% of the Full Scale Range (FSR), ensuring tight control of sensitive field equipment.

• Output Range: Delivers a standard 4-20 mA signal with a 6% over-range capability (up to 21.2 mA) to allow for specialized diagnostic signaling or high-scale travel.

• Over-range Protection: Robust electrical design provides continuous protection against voltages up to +42.5 VDC, preventing back-EMF or wiring faults from damaging the internal electronics.

• Pea Green Coding: Physically keyed and color-coded to ensure the module is only inserted into compatible analog output slots, preventing accidental hardware mismatches.

Technical Specifications

Technical FAQs

How does the 3805E handle a failure in one of its internal output legs?

The module uses TMR voting. If one leg fails, the other two legs continue to supply the correct current. The system logs a "Leg Fault" diagnostic, and the switch-over to the remaining healthy legs is nearly instantaneous (< 10 ms), meaning the field valve or actuator sees no disturbance.

Are the outputs on the 3805E isolated from one another?

No, the eight output points are DC-coupled and share a commoned return. When designing the field wiring, ensure that the loads are compatible with a common return architecture to prevent ground loops.

What is the "Pea Green" color code used for?

Triconex modules use a color-coding system to prevent maintenance errors. Pea Green specifically identifies Analog Output modules. The chassis slot and the module handle are matched to ensure the wrong module type is never energized in an AO slot.

Engineering & Installation Guide

• External Termination: The 3805E must be used with a compatible External Termination Assembly (ETA). The ETA provides the field-side screw terminals and fuses. Ensure the interface cable between the Triconex rack and the ETA is securely seated and shielded.

• Loop Powering: Since the module outputs 4-20 mA current, ensure the total loop resistance (including field wiring and the actuator impedance) does not exceed the module's driving capability. High resistance can lead to "Output Saturated" alarms.

• Hot-Swap Procedure: To replace a faulty 3805E, insert the new module into the adjacent "spare" slot (if configured) or directly replace the faulty unit. The TMR architecture will automatically synchronize the new module's outputs with the running safety logic without impacting the process.

• Thermal Considerations: In high-density racks, ensure that the cooling fans at the bottom of the Triconex chassis are functional. The 3805E generates heat during current regulation; maintaining the ambient air below 60 Celsius is critical for 0.25% accuracy.