Model Interpretation

3503E: TMR Digital Input Module, 24V AC/DC, SIL3

P/N: 3503E (base)

Compatibility: Tricon v9–v12 chassis (8110/8111/8112/8115/8116); hot‑swappable

Key Feature: 32 channels (8 groups × 4 commoned), 24V nominal, group‑isolated

Technical Parameters

Electrical & Input

Input Type: Dry/wet contact, 24V AC/DC nominal

Voltage Range: 20–42.5VDC (recommended); max 42.5VAC/VDC (47–63Hz AC)

Channels: 32, commoned in 8 groups (4 channels/group), group‑isolated

Input Current: ~6mA (on‑state)

Backplane Power: 24VDC (20.4–28.8VDC), ~120mA

Isolation: 1,500VDC group‑to‑backplane galvanic isolation

Redundancy & Safety

Architecture: Triple Modular Redundancy (TMR), 2oo3 voting

Safety Certification: IEC 61508 SIL3, TÜV, UL, CE, ATEX, FM

Diagnostics: >99.9% fault coverage; SOE (≤40ms resolution); open/short detection

MTBF: >160,000 hours

Mechanical

Form Factor: 3U, 19” rack, 1 slot

Dimensions (W×H×D): 114 × 30 × 185 mm

Weight: ~0.9 kg (2.0 lbs)

Mounting: Plug‑in backplane, hot‑swappable

Color Code: Dark Red

Environmental

Operating Temp: −40°C to +70°C

Storage Temp: −40°C to +85°C

Humidity: 5%–95% RH, non‑condensing

Diagnostics & Indicators

LEDs: PASS, FAULT, ACTIVE, TMR, ALARM

Fault Detection: Open/short circuit, channel mismatch, TMR deviation

Core Functions

24V AC/DC Safety Input for SIS

Optimized for 24V field devices (ESD pushbuttons, limit switches, proximity sensors); 32 commoned channels simplify wiring for large safety systems.

TMR Fault‑Tolerant Voting

Three independent input circuits per signal; 2oo3 voting eliminates single‑point failures—critical for SIL3 ESD/F&G/BMS loops.

Group Isolation & Noise Immunity

8 isolated groups reduce cross‑talk; opto‑isolation rejects ground loops and electrical noise—ideal for oil/gas/chemical plants.

Hot‑Swap & Online Maintenance

Replace module without system shutdown; supports online diagnostics and SOE logging for compliance.

Applications

Oil & Gas: ESD systems, 24V safety switches, F&G detectors

Chemical/Refining: Process interlocks, 24V discrete safety signals

Power Generation: Turbine ESD, boiler interlocks, BMS

SIS Retrofits: Upgrade legacy Tricon systems with SIL3 24V DI