Product Overview

The Allen-Bradley 1746-NT4 is a four-channel thermocouple and millivolt analog input module designed for the SLC 500 programmable controller platform. As a dedicated temperature input module, the 1746-NT4 accepts direct signals from thermocouple sensors and low-level millivolt devices, converting them to digital temperature data for use by SLC 500 processors without requiring external transmitters or signal conditioners. The module supports eight thermocouple types—J, K, T, E, S, R, B, and N—as well as direct ±50 mV and ±100 mV analog inputs, making it a versatile solution for temperature monitoring and low-level signal acquisition in industrial control systems .

Within the SLC 500 architecture, the 1746-NT4 occupies a standard chassis slot (any slot except slot 0, which is reserved for the processor) and draws power directly from the backplane, consuming 60 mA at 5V DC and 55 mA at 24V DC . The module features four backplane-isolated input channels with differential inputs, providing protection against ground loops and common-mode noise in electrically noisy industrial environments. Two integrated cold-junction compensation (CJC) thermistors on the removable terminal block ensure accurate temperature readings by measuring the terminal junction temperature and compensating for the thermocouple’s cold junction .

The Allen-Bradley 1746-NT4 distinguishes itself through its sigma-delta analog-to-digital conversion architecture, delivering 16-bit input resolution with update periods ranging from 26 milliseconds to 1.2 seconds depending on channel configuration and filter settings . The module provides open-circuit detection with selectable zero, upscale, or downscale response, and five green LED indicators—one for module status and one per channel—enable rapid visual diagnostics without programming software. The 1746-NT4 is compatible with both fixed and modular SLC 500 styles and supports remote I/O configurations with block transfers .

Technical Specifications