Model Interpretation

3708E: 8‑Ch TMR Thermocouple Input, isolated differential, TMR architecture

P/N: 3708E (E = enhanced diagnostic & extended temp range)

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

Key Difference from 3700/3701: Thermocouple‑specific input (vs. voltage‑only on 3700/3701)

Technical Parameters

Electrical & Input

Input Type: Isolated differential, thermocouple (K/J/E/T/R/S/B)

Channels: 8, isolated (channel‑to‑channel & field‑to‑backplane)

Input Range: ±20mV (thermocouple signal range)

Resolution: 16‑bit + sign

Accuracy: ±0.1% FSR (0–60°C, includes CJC)

Input Impedance: ≥10MΩ

Common‑Mode Rejection: ≥−120dB (DC–100Hz)

Response Time: <2s (all channels updated)

Backplane Power: 24VDC, ≤10W

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

Redundancy & Safety

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

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

Diagnostics: Per‑channel continuous diagnostics (open/short circuit, out‑of‑range, TMR mismatch); fault coverage >99.9%

MTBF: >120,000 hours

Mechanical & Environmental

Form Factor: 3U, 19” rack, 1 slot

Dimensions (W×H×D): 114 × 30 × 185 mm

Weight: ~1.2 kg

Color Code: Black (thermocouple module identifier)

Operating Temp: −40°C to +70°C

Storage Temp: −55°C to +85°C

Humidity: 5%–95% RH, non‑condensing

Protection Class: IP20 (panel‑mounted)

Diagnostics & Indicators

LEDs: PASS, FAULT, ACTIVE, TMR, ALARM

Fault Detection: Thermocouple open/short, over/under‑range, CJC fault, TMR deviation

Core Functions

8‑Channel High‑Precision Thermocouple Measurement

Directly interfaces with 7 common thermocouple types; built‑in CJC ensures accurate temperature readings from −200°C to +1800°C (sensor‑dependent).

TMR Fault‑Tolerant Temperature Monitoring

Three independent measurement circuits with 2oo3 voting; eliminates single‑point failures for SIL3 ESD/F&G/BMS temperature loops.

Isolated & Noise‑Immune Signal Conditioning

1,500VDC isolation and −120dB CMRR suppress ground loops and EMI; ideal for high‑noise oil/gas/chemical environments.

Hot‑Swap & Online Maintenance

Replace module without shutdown; per‑channel diagnostics and SOE logging support IEC 61511 compliance.

Continuous Sensor Health Monitoring

Detects thermocouple open/short circuits and drift; prevents nuisance trips from faulty temperature sensors.

Applications

Oil & Gas: ESD/F&G systems; furnace/reactor temperature monitoring (offshore/onshore)

Chemical/Refining: High‑temperature process loops; reactor/cracker thermocouple monitoring

Power Generation: Boiler/turbine ESD; high‑temperature combustion chamber monitoring

SIS Retrofits: Drop‑in upgrade for Tricon chassis requiring direct thermocouple input