Allen-Bradley 1746-NR4 RTD Resistance Input Module

The Allen-Bradley 1746-NR4 RTD/Resistance Input Module is a four‑channel analog input card for the SLC 500 family that directly reads RTD sensors and resistance inputs, delivering digital values to the backplane without an external power supply. Each channel is backplane isolated, enabling independent, noise‑tolerant measurements in mixed I/O environments. The module uses sigma‑delta conversion and offers programmable input filtering with notch options, including 2.62 Hz (10 Hz filter), 13.1 Hz (50 Hz), 15.72 Hz (60 Hz), and 65.5 Hz (250 Hz) to suit different power‑line interference scenarios. Key electrical specs include a very high common‑mode rejection (>150 dB at the 10 Hz/50 Hz/60 Hz filter frequencies) and normal‑mode rejection (>100 dB at 50 Hz/60 Hz), a maximum common‑mode voltage of ±1 V, and a per‑channel overload tolerance of ±5 V / ±5 mA. Backplane current draw is 50 mA at either 5 V or 24 V, with a maximum backplane power of 1.5 W, and no external power supply is required. Calibration is automatic: the module auto‑calibrates when a channel is enabled or when its input type, filter frequency, or excitation current changes, helping maintain measurement accuracy over time. The NR4 is compatible with any SLC 500 I/O chassis slot except slot 0 and provides four RTD/resistance inputs for straightforward integration with Allen‑Bradley controllers in industrial process and manufacturing environments.