Allen-Bradley 1794-OF4I Flex I/O Output Module

Allen-Bradley 1794-OF4I Flex I/O Isolated Analog Output Module

Product Introduction

The Allen-Bradley 1794-OF4I module belongs to the renowned Flex I/O family, known for its flexibility and reliability in distributed control systems. This isolated output module provides four independent analog outputs, which you can configure for various current or voltage ranges to suit your specific application needs. Its compact design and robust construction ensure dependable operation in demanding industrial environments. This module is a perfect choice for applications requiring precise control, such as valve positioning, actuator control, and signal conditioning.

Key Technical Specifications

The 1794-OF4I offers impressive technical capabilities for precise analog output control. It uses a digital-to-analog converter (DAC) with a resolution of 15 bits plus a sign bit. For voltage outputs, this translates to a fine resolution of 0.320 mV per count, and for current outputs, it provides 0.656 mA per count. The output signal update rate is user-selectable between 2.5 ms and 5.0 ms for all channels simultaneously, allowing you to balance speed and system loading.

Output Ranges and Configuration

You can configure each of the four isolated outputs independently for different signal types. The available current ranges are 4-20 mA and 0-20 mA. For voltage signals, the module supports ±10V DC, 0-10V DC, ±5V DC, and 0-5V DC ranges. Both voltage and current terminals remain at 0 output until the module receives a valid configuration from the controller. The maximum current load on the voltage output is 3 mA, while the resistive load for voltage outputs should be between 0 and 750 Ω.

Accuracy and Performance

The 1794-OF4I module delivers excellent accuracy with a rating of 0.1% of full scale at 25 °C for both voltage and current terminals. However, its performance across temperature variations is noteworthy. The voltage output accuracy drifts by only 0.0012% of full scale per degree Celsius, while the current output drifts by 0.0025% of full scale per degree Celsius. Furthermore, the module features a fast step response time of less than 25 µs to reach 63% of a full-scale step change.

Power and Environmental Parameters

Understanding the power requirements is crucial for proper installation. The 1794-OF4I requires an external DC supply with a nominal voltage of 24V DC. It can operate within a range of 19.2 to 31.2V DC, which includes a 5% AC ripple allowance. The module draws a maximum external DC supply current of 210 mA at 24V DC. For internal communication, it draws a FlexBus current of 50 mA at 5V DC. The maximum power dissipation is 4.7 W at 31.2V DC, and the maximum thermal dissipation is 16 BTU/hr. Under normal operating conditions, you can expect it to function reliably in ambient temperatures from 0 to 55 °C (32 to 131 °F).

Mechanical Specifications and Mounting

The Allen-Bradley 1794-OF4I is physically robust. It measures 3.7 x 2.6 x 3.7 inches (94 x 66 x 94 mm) and is designed to be mounted on a standard DIN rail or directly onto a panel. It can withstand vibration of 5g at 10 to 500 Hz and an operating shock of 30g, ensuring its resilience in high-vibration applications. The module has an open enclosure type. Importantly, the isolation voltage rating is contingent on the terminal base used: it provides 250V continuous isolation with a 1794-TBN base and 120V continuous isolation with other compatible bases like the 1794-TB2, 1794-TB3, 1794-TB3S, 1794-TB3T, or 1794-TB3TS.

Installation and Compatibility

This module is designed for easy integration into a Flex I/O system. It connects to the system via a compatible terminal base unit. You can use it with any available Flex I/O communication adapter, which makes it versatile for different network protocols. Furthermore, it is approved for use in hazardous locations, adding to its application flexibility. The 1794-OF4I is factory calibrated, but the design also provides an option for manual calibration if necessary, offering long-term precision.

Packaging List

Your shipment for the 1794-OF4I module will include the following items:

• (1) Allen-Bradley 1794-OF4I Flex I/O Isolated Analog Output Module

• (1) Product Installation Instructions Manual

• (1) Removable Terminal Block (RTB) connector (as required for the base unit)

Note: The terminal base unit (e.g., 1794-TB2, 1794-TB3T) and configuration software are sold separately.
All products are shipped via FedEx, UPS, or DHL.

Frequently Asked Questions (FAQ)

1. What are the mounting options for the 1794-OF4I module?
The 1794-OF4I can be easily mounted on a standard DIN rail or directly to a panel sub-plate. Its design ensures secure fastening in either installation method.

2. Do I need to buy a separate terminal base for this module?
Yes, the 1794-OF4I requires a compatible terminal base unit to connect to the Flex I/O system. It is compatible with bases like the 1794-TB2, 1794-TB3, or 1794-TBN.

3. How do I know which output type is active on the module?
The output type is user-configurable via the control system's software. The voltage and current terminals produce no output until you configure the module for the specific range.

4. What is the maximum continuous overload this module can handle?
The 1794-OF4I can withstand a maximum continuous overload of 30V or 32 mA, but only for one channel at a time. Exceeding this limit may cause damage.

5. What shipping carriers do you use?
We ship all orders for the 1794-OF4I via FedEx, UPS, or DHL to ensure fast and reliable delivery. The carrier will be selected based on your location and shipping option.