Features:
- Four inputs accept selectable voltage or current ranges with 14-bit conversion.
- Two ±10 V outputs update independently and include continuous short-circuit protection.
- The integral Remote I/O adapter uses switch-set addressing, transfer behavior, and link rate.
Allen-Bradley 1791-N4V2 combines analog acquisition, analog command, AC module power, and Remote I/O communication in one block.
Input wiring on 1791-N4V2 changes with voltage, customer-powered current, or block-powered current operation, while each channel retains its assigned return path.
Scanner configuration, switch settings, cable termination, and the 1791-N4V2 status indicators work together when diagnosing missing analog data.
The Allen-Bradley 1791-N4V2 Analog Block I/O Module may still be available for purchase and support from Apter Power beyond End-Of-Life (EOL) by the manufacturer (OEM).
Allen-Bradley 1791-N4V2 Block I/O Analog Module Manuals,Datasheets,Link
Important Notice: Other accessories, manuals, cables, calibration data, software, etc. are not included with this equipment unless listed in the above stock item description. All prices are shown in USD.
Selectable Analog Input Circuits
- Voltage path: Each channel provides a voltage input, return, and ground terminal for its configured range.
- Current path: Current signals enter through the current-input terminal and use the same channel return organization.
- Loop supply: A transmitter can use customer-supplied loop power or the module's 24 V DC terminal-25 source.
- Shunt limit: The 249 Ω current shunt is rated at 0.25 W, so loop conditions must remain within that boundary.
Switch and Scanner Coordination
- Rack address: SW1 assigns the Remote I/O rack number that the scanner uses to locate the block.
- Starting quarter: The first two SW1 positions select module groups 0, 2, 4, or 6 within the chosen rack.
- Transfer behavior: SW2 selects block or discrete transfer together with processor restart or lockout and output hold behavior.
- Communication rate: The 57.6, 115.2, or 230.4 kbit/s switch setting must match the scanner and every device on the link.
Two Voltage Command Channels
- Command conversion: The digital output word is converted into a 14-bit analog voltage for each of the two channels.
- Load requirement: Each ±10 V output must drive a load of 1 kΩ or greater to remain within the documented compliance.
- Update interval: Each output channel refreshes in 10 ms, independently of the 108 ms input-channel conversion.
- Fault tolerance: Indefinite short-circuit protection limits damage from a sustained output wiring fault.
Indicators and End Termination
- POWER indication: The POWER indicator confirms that the module's AC supply is present.
- COMM indication: Steady COMM shows an established Remote I/O exchange, while flashing reflects reset commands in program mode.
- FAULT indication: A lit or flashing FAULT state identifies module, low-power, cable, timing, or communication-loss conditions.
- End resistor: The final block uses 150 Ω at 57.6 or 115.2 kbit/s and 82 Ω at 230.4 kbit/s across BLU and CLR.