T8424
Description
1. Introduction
Purpose: Monitor discrete 120 VAC field devices (switches, contactors, relay contacts)
Architecture: TMR (3‑2‑0) + 1oo2D per‑channel voting
Safety: IEC 61508 SIL 3 / SIL 4 certified
Coating: Standard version (non‑coated); T8424C = acrylic conformal coated
Temp Range: 0 °C to +60 °C (T8424C: –40 °C to +70 °C)
Channels: 40 × 120 VAC digital inputs
Isolation: 2500 V DC optical (channel–channel, channel–system)
SOE: 1 ms resolution sequence‑of‑events logging
Hot‑Swap: Yes (online replacement)
2. Product Overview
40 × 120 VAC digital input channels (sink/source configurable)
Fully triplicated (TMR) input processing (three independent measurement lanes)
Sigma‑delta ADCs for high‑precision voltage sampling
Per‑channel 1oo2D voting for fault detection
Optical isolation (2500 V DC) between field and backplane
Onboard SOE (1 ms) for event time‑stamping
Independent line monitoring (open/short circuit) per channel
Front‑panel LEDs for channel status and module health
3. Specifications
3.1 Mechanical
Form Factor: T8000 chassis module, 56 mm wide, 6U
Dimensions (H×W×D): 255 mm × 56 mm × 210 mm
Weight: 1.3 kg (2.87 lbs)
Mounting: T8100 / T8400 chassis slots 1–16
Connectors: Front‑panel terminal blocks (TB1–TB5, 8 channels each)
PCB Protection: Standard (non‑coated); T8424C = acrylic conformal coating
3.2 Electrical
System Supply: 20–32 V DC (nominal 24 V DC)
Power Consumption: ≤ 5 W
Input Channels: 40 × 120 VAC digital inputs
Input Voltage Thresholds:
Logic 1: 90–150 V AC
Logic 0: <30 V AC
Input Current: ~4 mA per channel (at 120 V AC)
Input Type: Sink (NPN) / Source (PNP) configurable
Isolation: 2500 V DC optical barrier (channel–channel, channel–system)
Backplane Interface: Trusted Backplane Bus (TBB), TMR
3.3 Functional
Voting: 1oo2D per channel (triple measurement + comparison)
SOE Resolution: 1 ms (per channel state change)
Diagnostics:
Open‑circuit detection (per channel, with line resistor)
Short‑circuit detection (per channel)
Onboard BIST (Built‑In Self‑Test)
Fault logging to system HMI
Response Time: ≤ 2.0 ms (channel to backplane)
Data Integrity: BER < 10⁻¹²
3.4 Environmental
Operating Temperature: 0 °C to +60 °C (standard)
Storage Temperature: –40 °C to +85 °C
Humidity: 5–95 % RH, non‑condensing
Altitude: ≤ 2000 m
Vibration: IEC 60068‑2‑6 (1 g, 10–150 Hz)
Shock: IEC 60068‑2‑27 (15 g, 11 ms)
3.5 Safety & Certification
Safety Standard: IEC 61508 SIL 3 / SIL 4
Certifications: CE, UL, CSA, ATEX II 3G Ex ec IIC T4 Gc, IECEx
Fault Tolerance: TMR (3‑2‑0), 1oo2D per channel
PFHd: < 8.0 × 10⁻¹⁰ / h (SIL 4)
4. Front Panel & Indicators
PWR (Green): On = Module power OK; Off = No power
RUN (Green): On = Module active; Flashing = Initialization / BIST
FAULT (Red): On = Module/channel fault; Flashing = Minor fault
COM (Green): Flashing = Backplane communication active
TB1–TB5: 5 × terminal blocks (8 channels each, 120 VAC inputs)
FG: Functional Ground (chassis earth)
5. Installation & Wiring
Chassis Mounting: Align with empty slot in T8100/T8400 chassis, insert firmly, tighten front‑panel screws (torque 0.8–1.0 Nm)
Field Wiring: For each terminal block, connect 120 VAC L to group common terminal, field device output to channel input terminal, device common to 120 VAC N
Wire Gauge: 16–22 AWG stranded wire; torque terminals to 0.5–0.6 Nm
Line Resistors: 10 kΩ for open‑circuit monitoring (per channel)
Hot‑Swap: Supported; system auto‑detects new module without shutdown
6. Operation & Diagnostics
Power‑up: PWR ON; RUN flashes during self‑test (5–10 s)
Normal Operation: PWR + RUN steady GREEN; FAULT OFF; COM flashing
Fault Conditions: FAULT ON = critical fault (channel short/open, TMR mismatch); FAULT Flashing = minor fault (single‑lane mismatch)
SOE Logging: All state changes time‑stamped (1 ms) and stored in system memory
7. Ordering Information
T8424: Standard 40‑Ch 120 VAC DI (0 °C … +60 °C)
T8424C: Conformal coated, –40 °C … +70 °CRockwell Automation
TC‑8424: Terminal Block Cable Kit (field wiring)
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