The 1746-NI4 is a 4-channel analog input module for the Allen-Bradley SLC 500 platform, designed to interface process signals such as pressure, flow, temperature, and level into the PLC for monitoring and control. Each of the four channels can be individually configured via on-board DIP switches for current input (±20 mA nominal, ±30 mA max) or voltage input (±10 VDC), allowing flexible connection of transmitters and signal sources. The module occupies a single I/O slot (any slot except 0) in a 1746 chassis and communicates with the SLC processor over the backplane.
Internally, the 1746-NI4 uses delta-sigma A/D conversion to produce 16-bit two’s complement data, coded from −16,384 to +16,384 for current inputs and −32,768 to +32,767 for voltage inputs, delivering high resolution for tight control. It features an effective bandwidth of 10 Hz, typical update time of 512 µs, and step response around 60 ms, with overall accuracy around ±0.3–0.4% of full scale at 25 °C depending on mode. Input impedance is approximately 250 Ω for current inputs and 1 MΩ for voltage inputs.
The module draws about 35 mA at 5 VDC and 85 mA at 24 VDC from the backplane and does not require an external 24 V supply. It supports differential wiring per channel to help reject common‑mode noise, but the channels are non-isolated from each other, sharing a common reference. A removable terminal block provides screw terminal connections for the four input channels and associated commons, and standard analog cables (0.5–5 m with 15‑pin D‑shell AIFM connectors) are available for panel wiring.
Typical applications include connecting 4–20 mA transmitters, ±10 V signals from drives or positioners, and other process instruments into SLC 500 systems used in water treatment, manufacturing, and building automation.
