The Allen-Bradley 1746-INT4/C, also cataloged as the 1746INT4 Thermocouple Input Module, operates as a dedicated hardware component for low-level millivolt and temperature signal acquisition within SLC 500 programmable controller systems.

Catalog Suffix Matrix

• Base Model: 1746-INT4
• Revision Suffixes: 1746-INT4/B, 1746-INT4/C
• Platform Series: SLC 500
• Function Class: Isolated Analog Input

Hardware Specifications

Network Backplane Communication and I/O Scaling

The module communicates via the proprietary chassis backplane bus, utilizing established communication velocity licenses to interface directly with the CPU. It handles discrete channel inputs through high-density scaling algorithms while supporting firmware flash compatibility across standard SLC 500 rack environments. Real-time data updates synchronize with the controller scan cycle to maintain deterministic loop performance.

Ordering Information

• 1 1746-INT4 Thermocouple Input Module unit
• 1 Removable terminal block connector interface

Physical Installation Procedures

• Chassis Slot Placement: Insert the module into any available I/O slot of an SLC 500 modular chassis, ensuring the backplane connector aligns securely without forcing.
• Wiring Shielding: Terminate all thermocouple extension wire shields to a dedicated ground bus to mitigate electromagnetic interference and common-mode voltage spikes.
• Terminal Torquing: Secure all field input wires within the removable terminal block using proper screwdriver torque limits to prevent intermittent electrical connections.

Frequently Asked Questions

• Q: Does the 1746-INT4 module support live hot-swapping inside a powered chassis?
• A: No. Power to the chassis rack must be completely disconnected before inserting or removing the module to prevent electrical damage to the backplane bus.
• Q: What is the primary function of the voltage input ranges supported?
• A: The module accepts low-level millivolt signals ranging from -50 to 50 MVDC and -100 to 100 MVDC, suitable for direct thermocouple transducer interfacing.
• Q: How is operating power supplied to internal module circuitry?
• A: Power is drawn directly from the chassis power supply through the backplane, consuming 110 mA at 5 VDC and 85 mA at 24 VDC.
• Q: Are input channels electrically isolated?
• A: Yes, the module features built-in channel isolation to protect against ground loops and common-mode voltage transients across industrial measurement points.
• Q: Can this module interface with modern ControlLogix controllers directly?
• A: No. It is physically and logically engineered exclusively for the legacy Allen-Bradley SLC 500 modular hardware rack architecture.
• Q: What indicates a normal operational state on the front faceplate?
• A: Operational status is communicated via diagnostic LED indicators that display hardware health and active communication states with the processor.
• Q: What gauge of wire should be used for terminal connections?
• A: Use twisted-pair copper thermocouple extension wires sized between 22 AWG and 14 AWG for optimal signal integrity.
• Q: Is field calibration required during initial deployment?
• A: Factory calibration is preset, but software configuration scaling within the programming environment must match the specific thermocouple type attached.