Allen-Bradley 1794-IE8 FLEX I/O 8-Channel Analog Input

Eight analog inputs for FLEX I/O racks

The Allen-Bradley 1794-IE8 is a FLEX I/O analog input module that reads eight single-ended signals. Each input has a current terminal for 4-20 mA or 0-20 mA loops and a voltage terminal for 0-10 V or ±10 V signals, so a single module serves transmitters, potentiometers and other sensors mounted on a terminal base in a field enclosure. The module mounts on a 1794 terminal base and is connected through the FLEX I/O backplane (Flexbus) to an adapter that links the rack to EtherNet/IP, ControlNet, DeviceNet or another network.

Resolution is 12 bits unipolar and 11 bits plus sign bipolar, accuracy is 0.20 percent of full scale at 25 °C, and all channels convert in 256 microseconds. Rockwell states that no calibration is required.

Technical specifications

Wiring and configuration

Choose between the current terminal and the voltage terminal on each channel when wiring the base: current signals go to a 238 ohm input, voltage signals to a 100 kilohm input. Only one channel at a time may be overloaded, up to 30 V continuous or 32 mA continuous. The module needs 24 V DC user power in the 10.5 to 31.2 V range, drawing 60 mA, and a small 15 mA from the Flexbus.

The module has a green power indicator. Set the keyswitch on the terminal base to position 3 before seating the module, and do not remove or replace a terminal base with power applied because backplane interruption can cause unintended operation. Use the terminal base that suits your field wiring: the cage-clamp 1794-TB2 and 1794-TB3, or the spring-clamp 1794-TB3S.

Related FLEX I/O analog modules

The same installation document covers the 1794-OE4 four-channel analog output module and the combined 1794-IE4XOE2 with four inputs and two outputs. Choose the IE8 when you only need inputs and want the maximum channel count in one module. Confirm that the adapter in the rack supports the module and its series.

Documents and quotation

The Rockwell Automation installation instructions for the 1794-IE8, 1794-OE4 and 1794-IE4XOE2 modules are attached. See our PLC and I/O cards catalogue for related controllers and I/O, including the 1734-IB8 POINT I/O module. Confirm the exact catalog number, series letter and firmware or hardware revision on the product label, and the compatibility with your existing system, before ordering. Stock and lead time are confirmed at quotation.

How the 1794-IE8 Works

A FLEX I/O system is built from an adapter and up to several I/O modules, each sitting on its own terminal base, linked by the Flexbus backplane that runs through the bases. The adapter exchanges data with the controller over the network, and the 1794-IE8 passes its eight converted input values to the adapter across the Flexbus. Field wiring stays on the terminal base, so a module can be exchanged without disturbing the wires.

Each channel has two input paths: a current terminal with a low-value shunt and a high-impedance voltage terminal. The successive-approximation converter samples all channels quickly, and the module filtering, described by the normal mode rejection figures above, smooths high-frequency noise. Range selection is made in the configuration data sent by the controller, and the result is presented as a left-justified 16-bit value that the controller scales to engineering units.

1794-IE8 Selection & Ordering Guide

• Inputs only or mixed: choose the 1794-IE8 for eight inputs; the 1794-OE4 provides outputs and the 1794-IE4XOE2 combines four inputs with two outputs.
• Terminal base: order a compatible base, such as the 1794-TB3 or 1794-TB3S, if the module is not going onto an existing base, and set its keyswitch to position 3.
• Adapter: confirm the FLEX I/O adapter and network (EtherNet/IP, ControlNet, DeviceNet or other) and its support for the module series.
• Isolation: the channels are not isolated from each other. Where isolation is required, ask about isolated FLEX I/O analog modules.
• Harsh environments: FLEX I/O-XT variants exist for extended temperature and conformal coating; check the selection guide for the matching catalog number.

When you request a quote for the 1794-IE8, include the series letter and the adapter type. Our team can help confirm the correct ordering code.

Installation & Maintenance

Mount the terminal base on the DIN rail, connect it to the neighbouring base, set the keyswitch and then seat the module. Wire 24V DC user power to the base, use shielded cable for analog signals, ground the shield at one point and keep analog cables away from power and drive wiring. During maintenance, check the green power indicator, review channel data and status in the controller, and verify each channel with a calibrated current or voltage source.

Typical Applications in Oman & the GCC

• Remote I/O in oil and gas gathering stations and process skids.
• Water treatment, pumping and desalination plants with many transmitters in field cabinets.
• Power generation balance-of-plant and utility monitoring.
• Upgrades and spares for existing FLEX I/O installations.

Why Source the 1794-IE8 from Seven Star LLC

Seven Star LLC supplies Allen-Bradley FLEX I/O modules and terminal bases, including the 1794-IE8, across Oman and the GCC. Request a quote with the catalog number and quantity, and our team can help confirm the correct ordering code.