Invensys Triconex 3505E 32-Ch Digital Input 24VDC TMR

Product Overview

The 3505E is a 32-channel digital input module manufactured by Invensys Triconex for the Tricon safety instrumented system (SIS). Designed with Triple Modular Redundancy (TMR) architecture, it acquires discrete signals from field switches, proximity sensors, and safety interlocks at 24 VDC nominal voltage. The module delivers high-density input capacity with 1500 V AC isolation between field channels and logic circuitry, ensuring reliable signal detection for emergency shutdown (ESD) and fire & gas (F&G) applications.

Key Specifications

• System: Invensys Triconex Tricon SIS
• Type: TMR Digital Input Module
• Channels: 32 digital inputs
• Nominal Input Voltage: 24 VDC
• Input Voltage Range: 20–28 V AC/DC
• Input Current: 6 mA typical
• Input Impedance: 4 kΩ typical
• Isolation Voltage: 1500 V AC (channel to logic)
• Input Signal Delay: 4 ms
• Operating Temperature: -40°C to +70°C
• Storage Temperature: -40°C to +85°C
• Humidity: 5% to 95% RH, non-condensing
• Dimensions: 10.2 × 6.3 × 3.1 inches
• Weight: 2.2 kg

Features & Benefits

1. TMR Fault Tolerance: Triple Modular Redundancy ensures continuous operation with correct output even if one channel fails, eliminating single points of failure.
2. High Channel Density: 32 inputs in a single slot optimize rack space and reduce per-point hardware costs in large safety systems.
3. Robust Isolation: 1500 V AC galvanic isolation protects sensitive TMR logic from field-side transients and ground faults.
4. Wide Voltage Range: 20–28 V AC/DC input range accommodates plant voltage variations and battery-backed UPS systems.
5. Fast Response: 4 ms input delay provides rapid safety interlock detection for emergency shutdown applications.

FAQ

Q: What is the difference between 3505E and 3503E?
A: The 3505E is a 32-channel 24 VDC digital input module. The 3503E is a 24 VAC/VDC digital input module with different voltage thresholds. Both use TMR architecture.

Q: Does the 3505E support dry contact inputs?
A: The module is designed for 24 VDC wet contact inputs. For dry contact applications, external pull-up resistors or wetting voltage sources are required.

Q: Can the 3505E be used in non-safety PLC applications?
A> While electrically compatible with standard 24 VDC inputs, the 3505E is optimized for SIL-rated Tricon safety systems. For non-safety PLC applications, standard Allen-Bradley or Siemens input modules may be more cost-effective.

Installation Guide

• Install the module into a Tricon chassis slot designated for digital input modules.
• Connect 24 VDC field power to the external termination panel (ETP) or direct wiring terminal.
• Wire each input channel to the corresponding field device contact (switch, relay, or sensor output).
• Verify ETP fuse ratings match the module's input current requirements.
• Check each channel's ON/OFF status LED against field device state during commissioning.

Selection Tips

• Input Count: The 3505E provides 32 inputs. For lower density requirements, consider 16-channel Tricon DI modules.
• Voltage Standard: Confirm your plant safety loop voltage is 24 VDC. For 115 VAC or 48 VDC applications, select 3501E or 3502E respectively.
• ETP Matching: The 3505E requires a compatible external termination panel. Verify ETP part number and cable assembly compatibility with your Tricon chassis generation.