Allen-Bradley 1746-NR4 4-Channel Resistance Input Module

The Allen-Bradley 1746-NR4 is a four‑channel RTD/Resistance Input module for SLC 500 controllers, providing isolated, four‑channel RTD/resistance sensing in a compact single‑slot I/O card. Each channel accepts RTD and fixed resistance sensors, supports independent configuration, and features a dedicated LED per channel plus a module status indicator for quick diagnostics. The module is backplane‑isolated and designed to sit in any I/O slot except slot 0, with a backplane power draw of up to 1.5 W (typical 50 mA at 5 V and 50 mA at 24 V) and no external power supply required. Its analog front end uses a sigma‑delta ADC with low‑pass digital filtering and programmable notch frequencies to tailor noise rejection, delivering high common‑mode and normal‑mode rejection (greater than 150 dB and 100 dB, respectively, at common filter frequencies). The NR4 provides a maximum common‑mode input voltage of ±1 V and a maximum overload of ±5 V/±5 mA per channel, with auto‑calibration when a channel is enabled or its input type or filter/excitation settings are changed. Overall, the 1746-NR4 delivers four isolated input channels suitable for precision resistance or RTD measurements in industrial environments, making it a common choice for temperature monitoring and resistance‑based sensing in SLC 500 installations.