Allen-Bradley 1794-IJ2 Flex I/O Frequency Input Module Guide

Product Overview

When you need precise frequency measurement in a distributed I/O system, the Allen-Bradley 1794-IJ2 delivers reliable performance. This Flex I/O module from Rockwell Automation accepts frequency inputs from 1 to 32 kHz for both sine and square wave signals. It features two channels, each with dedicated frequency and gate inputs, making it ideal for high-speed counting and monitoring applications.

Technical Specifications

The 1794-IJ2 operates on an external DC supply range of 19.0 to 31.2V DC (including 5% AC ripple). It draws 30 mA at 5V DC from the FlexBus. The module accepts input frequencies from 1 to 32 kHz for sine wave and square wave signals, with a minimum input pulse width of 20 µs. Raw frequency values can reach a maximum of 32,767 or 3,276.7, depending on the selected range. The module provides two isolated 24V DC outputs, each capable of sourcing up to 1.0 A per channel. Output on-state voltage is 24V DC nominal, with a minimum of 10V DC and a maximum of 31.2V DC. On-state current is 9.0 mA typical. The module dissipates a maximum of 4.6W at 31.2V DC, with thermal dissipation up to 15.6 BTU/hr. It mounts on a DIN rail and requires a terminal base such as the 1794-TB3G or -TB3GS. Wire size depends on the installed terminal base.

Industry Applications

The 1794-IJ2 excels in applications requiring accurate frequency measurement, such as monitoring motor speed, conveyor belt velocity, or turbine rotation. In a packaging line, it can track the frequency of a rotating encoder to synchronize cut-and-seal operations. For pump monitoring, the module measures input frequency from a flow meter, enabling precise flow control. Its two isolated outputs can trigger alarms or control actuators when frequency exceeds set thresholds.

Installation & Setup Guidance

Mount the 1794-IJ2 on a DIN rail using the 1794-NM1 mounting kit if needed. Ensure the FlexBus connector is fully inserted into the terminal base. Use a 1794-TB3G or -TB3GS terminal base for wiring. Connect the external DC supply within the 19.0 to 31.2V DC range. Wire frequency and gate inputs per channel, observing polarity. The module's front panel includes input, output, and power status indicators for quick diagnostics.

Selection Guide & Purchasing Advice

Before purchasing the 1794-IJ2, verify your system's compatibility with Flex I/O architecture. Confirm the required terminal base (1794-TB3G or -TB3GS) and ensure your DC supply meets the 19.0 to 31.2V DC range. For complete technical specifications, please contact BluePLC Industrial. BluePLC Industrial stocks genuine Allen-Bradley modules and can advise on current availability and any replacement options if needed.