Allen-Bradley 1746-NT8 – 8-Point Thermocouple/mV Analog Input Module | SLC 500 Platform
Engineering Background
The Allen-Bradley 1746-NT8 is a precision analog input module designed for the SLC 500 modular I/O system. It provides eight isolated thermocouple or millivolt input channels, enabling high-accuracy temperature and low-level signal acquisition in demanding industrial environments. As part of Rockwell Automation’s proven SLC 500 family, this module integrates seamlessly with SLC 5/01 through SLC 5/05 processors and is widely deployed across process, discrete, and hybrid manufacturing applications.
Product Positioning
Targeted at procurement engineers and maintenance teams managing legacy SLC 500 infrastructure, the 1746-NT8 delivers reliable thermocouple signal conditioning without requiring a full system upgrade. Konmask.com supplies verified surplus and refurbished units with full functional testing, supporting both emergency replacement and planned MRO procurement cycles.
Complete Technical Specifications
- Catalog Number: 1746-NT8
- Platform: Allen-Bradley SLC 500 Modular I/O
- Module Type: Analog Input — Thermocouple / Millivolt
- Number of Input Channels: 8 (individually isolated)
- Input Types Supported: J, K, E, T, R, S, B thermocouples; ±100 mV, ±50 mV, ±25 mV ranges
- Resolution: 16-bit (±32,767 counts full scale)
- Accuracy: ±0.1% of full scale (typical at 25°C)
- Cold Junction Compensation: Automatic, internal sensor
- Input Impedance: >10 MΩ
- Common Mode Rejection: 120 dB at 50/60 Hz
- Normal Mode Rejection: 60 dB at 50/60 Hz
- Backplane Current Draw: 150 mA @ 5 VDC; 0 mA @ 24 VDC
- Power Dissipation: 0.75 W (max)
- Operating Temperature: 0°C to +60°C (32°F to 140°F)
- Storage Temperature: -40°C to +85°C
- Relative Humidity: 5% to 95% non-condensing
- Dimensions (H × W × D): 111.8 mm × 40.6 mm × 87.4 mm
- Weight: Approx. 200 g
- Agency Certifications: UL Listed, CE Marked, CSA Certified
- Firmware: No user-configurable firmware; configured via RSLogix 500 / RSLogix Micro
Proven Application Environments
- Food & Beverage: Oven temperature profiling, pasteurization loop control, CIP temperature monitoring
- Chemical Processing: Reactor temperature acquisition, exothermic process monitoring
- Plastics & Rubber: Extruder barrel zone temperature control, mold temperature feedback
- HVAC & Building Automation: Multi-zone air handling unit temperature sensing
- Metals & Heat Treatment: Furnace profiling, quench bath monitoring
- Pharmaceutical: Autoclave and sterilization cycle temperature validation
- Water & Wastewater: Process temperature trending in treatment facilities
Engineering Advantages
- 8-Channel Density: Maximizes chassis slot utilization — one module replaces up to eight discrete analog input cards in legacy configurations.
- Individual Channel Isolation: Eliminates ground loop interference between sensors, critical in multi-point thermocouple installations.
- Automatic Cold Junction Compensation: Reduces field wiring complexity and eliminates the need for external reference junction hardware.
- Universal Thermocouple Support: Accepts J, K, E, T, R, S, and B type thermocouples — a single module covers the full range of industrial temperature measurement requirements.
- High CMR (120 dB): Ensures signal integrity in electrically noisy industrial environments with VFDs, motors, and switching power supplies.
- Native SLC 500 Integration: Plug-and-play compatibility with all SLC 500 modular chassis; no special adapter or bridge required.
- RSLogix 500 Configuration: Fully configurable via standard Rockwell software — no proprietary tools or additional licensing required.
System Architecture & Signal Flow
The 1746-NT8 occupies one slot in any SLC 500 modular chassis (1746-A4 through 1746-A13). Each of the eight input channels connects directly to a thermocouple or millivolt source via screw-terminal wiring. The module’s internal 16-bit ADC samples each channel sequentially, applies automatic cold junction compensation, and converts the raw signal to engineering units (°C, °F, or raw counts) based on the channel configuration set in RSLogix 500. Data is transferred to the SLC processor via the backplane on each scan cycle. The processor maps the module’s input image to the input data file (I:x.0 through I:x.7), making all eight channel values directly accessible in ladder logic without additional MSG instructions.
Sourcing & Quality Verification
- Stock Origin: Verified surplus from decommissioned OEM and end-user installations; no counterfeit risk — all units inspected against Rockwell Automation reference standards.
- Functional Testing: Each unit undergoes power-on verification, backplane communication check, and channel-level signal injection testing prior to shipment.
- Visual Inspection: PCB, connector pins, terminal blocks, and housing inspected for damage, corrosion, and component integrity.
- Packaging: Anti-static bag + foam-lined carton; ESD-safe handling throughout.
- Documentation: Original Rockwell Automation datasheet and wiring diagram available upon request.
- Warranty: 12-month Konmask operational warranty covering functional defects under normal operating conditions.
Procurement Process
- Confirm Requirement: Verify catalog number 1746-NT8 against your existing chassis and processor revision. Confirm thermocouple type(s) in use.
- Request Quote: Contact Konmask via email or phone with quantity, required delivery date, and destination port/Incoterm.
- Order Confirmation: Purchase order accepted; lead time confirmed (typically 1–5 business days for in-stock units).
- Shipment: Dispatched via DHL / FedEx / SF Express with full tracking. Export documentation (commercial invoice, packing list, COO) provided for cross-border shipments.
- Incoming Inspection: Konmask recommends a 48-hour incoming inspection window before installation.
- Technical Support: Post-delivery configuration and commissioning support available via email at support@konmask.com.
Technical FAQ
Q: Is the 1746-NT8 compatible with SLC 5/01 processors?
A: Yes. The 1746-NT8 is compatible with all SLC 500 modular processors: SLC 5/01, 5/02, 5/03, 5/04, and 5/05. It is not compatible with SLC 500 fixed (1747-L20/L30/L40) or MicroLogix platforms.
Q: Can I mix thermocouple types across the 8 channels?
A: Yes. Each channel is independently configurable for thermocouple type and engineering unit output via RSLogix 500. You can run J-type on channels 0–3 and K-type on channels 4–7 simultaneously.
Q: What is the update rate per channel?
A: The module scans all 8 channels sequentially. Total update time is approximately 160 ms for all 8 channels (≈20 ms per channel). This is suitable for temperature control loops but not for high-speed transient capture.
Q: Does the module require external 24 VDC power?
A: No. The 1746-NT8 draws power exclusively from the SLC 500 backplane (5 VDC, 150 mA). No external 24 VDC supply is required.
Q: What is the difference between 1746-NT8 and 1746-NT4?
A: The 1746-NT4 provides 4 thermocouple/mV input channels; the 1746-NT8 provides 8 channels. Both share the same signal types and accuracy specifications. Choose NT8 when channel density is a priority.
Q: Can Konmask provide a test report for the unit?
A: Yes. A functional test report is available upon request at time of order. Please specify this requirement in your purchase order or RFQ.
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