1791-NDC Allen-Bradley Analog Block I/O Module
Product Introduction
The Allen-Bradley 1791-NDC module brings reliable analog control to industrial systems. You get 4 analog inputs and 2 current outputs in one block. This device works with a 24V DC power supply drawing only 600 mA.
Additionally, it communicates seamlessly with PLC-2, PLC-3, PLC-5/250, PLC-5, and SLC5/02 controllers. Many engineers choose the 1791-NDC for its selectable input ranges. For instance, you can set inputs for ±10V, 0-20 mA, or ±20 mA. Therefore, this module fits diverse signal types.
Technical Specifications
The 1791-NDC offers high precision. Input resolution reaches 14 bits. The update rate per channel is 108 ms. Input impedance measures 10 megaohms for voltage and 250 ohms for current. Absolute accuracy stays at 0.1% at 25°C.
Meanwhile, the two current outputs provide 0-20 mA range. Output resolution is 13 bits. Internal update rate per channel is 10 ms. Short circuit protection is indefinite. Absolute output accuracy also reaches 0.1% at 25°C.
Power dissipation maxes at 11.52 W. Thermal dissipation reaches 39.28 BTU/hr. The input bandwidth is fixed at 5 Hz. Overvoltage protection handles up to 140V AC.
Mechanical and Environmental Data
The 1791-NDC module measures 6.95 x 2.7 x 3.85 inches. It weighs only 1.00 lbs. Operating voltage range is 19.2 to 30V DC.
Installation Guidelines
First, disconnect all power before handling the 1791-NDC. Next, mount the block on a DIN rail or panel. Then, connect the 24V DC supply to the appropriate terminals. After that, wire analog inputs using shielded cables. Finally, set input jumpers according to your signal type.
Furthermore, always verify polarity for current loops. The module includes a current-limited voltage source for loop-powered transducers. Therefore, external loop supplies are often unnecessary.
Packaging List
Allen-Bradley 1791-NDC Analog Block I/O Module – 1 unit
Terminal block (factory attached)
Product label and basic wiring diagram
Shipping via FedEx, UPS, or DHL.
Frequently Asked Questions (FAQ)
1. Which controllers work with the 1791-NDC?
The 1791-NDC is compatible with PLC-2, PLC-3, PLC-5/250, PLC-5, and SLC5/02 controllers.
2. Can I use both voltage and current inputs together?
Yes. Each of the 4 analog inputs on the 1791-NDC can be configured independently for voltage or current ranges.
3. What happens if an output shorts?
The 1791-NDC supports indefinite short circuit protection on its current outputs, so no damage occurs.
4. How fast does the module update outputs?
Each current output updates internally every 10 milliseconds, while inputs update every 108 ms.
5. Do I need an external power supply for 4-20 mA sensors?
No. The 1791-NDC provides a 24V DC current-limited voltage source for loop-powered transducers.
