Product Overview of the Allen-Bradley 1794-OE4

The Allen-Bradley 1794-OE4 is a versatile analog output module. Specifically, it belongs to the popular 1794 Flex I/O product family. This module features four (4) single-ended analog output channels. Therefore, it controls multiple modulating devices simultaneously. The 1794-OE4 supports both current and voltage output signals. Furthermore, all channels are user-configurable for different signal types. Consequently, this module suits diverse process control applications.

Output Signal Types and Ranges

The 1794-OE4 offers four configurable output signal types. For current outputs, you can choose 4-20 mA or 0-20 mA ranges. For voltage outputs, you can choose ±10 VDC or 0-10 VDC ranges. Therefore, this module works with various final control elements. Typical applications include variable frequency drives (VFDs). Similarly, it controls modulating control valves and converters. The module also positions dampers, louvers, and transducers.

Resolution and Data Format

The 1794-OE4 provides 12-bit plus sign resolution. The voltage resolution is 2.56 mV per count. Similarly, the current resolution is 5.13 μA per count. Therefore, you achieve smooth and precise analog control. The module stores analog data in a specific register format. This format is left-justified, 16-bit 2's complement. Consequently, programming integration is straightforward.

Conversion Method and Speed

The 1794-OE4 uses pulse width modulation (PWM) for conversion. This conversion method is reliable and accurate. The maximum conversion rate for all channels is 1.024 ms. Therefore, the module updates outputs very quickly. This speed suits applications requiring fast response times. The output step response time is 24 ms for voltage outputs. This represents 63% of the full-scale setting.

Accuracy and Thermal Drift

The current output accuracy is 0.425% full scale at 25°C. The current accuracy drift is 0.0069% full scale per °C. Similarly, the voltage output accuracy is 0.133% full scale at 25°C. The voltage accuracy drift is 0.0045% full scale per °C. Therefore, the 1794-OE4 maintains good accuracy across temperatures. The module does not require calibration. Consequently, long-term stability is excellent.

Output Load Specifications

For current outputs, the resistive load range is 15 to 750 Ω. Therefore, the 1794-OE4 drives most analog receivers reliably. For voltage outputs, the maximum current load is 3 mA. Consequently, connect voltage outputs to high-impedance inputs only. Always verify your field device compatibility before wiring.

Power Consumption and Thermal Characteristics

The 1794-OE4 draws a Flexbus current of 20 mA at 5V DC. Its external DC supply range is 10.0 to 31.2V DC. This range includes 5% AC ripple allowance. The nominal external supply is 24V DC. Therefore, standard industrial power supplies work perfectly. The external DC supply current is 70 mA at 24V DC.

Maximum power dissipation is 4.5W at 31.2V DC. Maximum thermal dissipation is 13.6 BTU/hour at 31.2V DC. Consequently, the 1794-OE4 generates moderate heat. Ensure proper ventilation in your control cabinet.

Isolation and Protection Features

The 1794-OE4 provides continuous isolation voltage of 50V. This isolation exists between I/O and the system. However, no individual channels are isolated from each other. Therefore, all channels share a common reference. This non-isolated design suits most applications. For isolated channel requirements, consider other Flex I/O modules.

Compatible Terminal Base Units

The 1794-OE4 works with many terminal base units. Specifically, compatible bases include 1794-TB2, 1794-TB3, 1794-TB3S, 1794-TB3T, 1794-TB3TS, and 1794-TBN. The required keyswitch position is 4. Therefore, verify your base configuration before installation. Only one terminal base is needed per module. The terminal base provides DIN rail attachment. It also offers output signal wiring termination points.

Compatible Communication Adapters

The 1794-OE4 works with various Flex I/O communication adapters. For example, it pairs with 1794-ACN15 and 1794-ACNR15 for ControlNet. Similarly, 1794-AENT and 1794-AENTR provide EtherNet/IP connectivity. The module also works with 1794-AND for DeviceNet. Furthermore, 1794-ASB and 1794-APB adapters enable Remote I/O and Profibus. Consequently, the 1794-OE4 integrates into many network architectures. It can also work with MicroLogix compact controllers via appropriate adapters.

Status Indicators and Diagnostics

The 1794-OE4 features one green and red power and status indicator. This dual-color LED shows module health at a glance. A green light indicates normal operation. In contrast, a red light signals a fault condition. Therefore, troubleshooting becomes quick and straightforward. The module has an open-type enclosure. Consequently, the entire Flex I/O assembly must be installed inside a protective cabinet.

Environmental Specifications

You can operate the 1794-OE4 between 0 to 55 °C (32 to 131 °F) . The storage temperature range is -40 to 85 °C (-40 to 185 °F) . Relative humidity can range from 5 to 95% non-condensing. Operating shock rating is 30g. Vibration tolerance is 5g at 10 to 500 Hz. Therefore, this module suits most industrial environments.

Installation Guidelines for the 1794-OE4

First, mount the compatible terminal base on a DIN rail. Second, set the keyswitch to position 4. Third, snap the 1794-OE4 onto the terminal base. You can install or remove this module under power. However, always exercise caution during hot insertion. Fourth, connect your analog receivers to the appropriate terminals. For current outputs, use twisted-pair shielded cables. For voltage outputs, keep cable lengths short. Fifth, apply external DC power to the terminal base. Finally, configure the output signal ranges in your control program.

Physical Dimensions

The 1794-OE4 measures 94.0 x 94.0 x 53.3 mm. In inches, this is 3.7 x 3.7 x 2.1 inches. Therefore, it occupies minimal panel space. The compact design suits dense control cabinets.

Package Contents

• One Allen-Bradley 1794-OE4 Flex I/O Analog Output Module

• One product information sheet with wiring diagrams

• One label sheet for channel identification

• No terminal base unit included (sold separately)

Frequently Asked Questions (FAQ)

Q1: What terminal base units work with the 1794-OE4?
A: The 1794-OE4 works with 1794-TB2, 1794-TB3, 1794-TB3S, 1794-TB3T, 1794-TB3TS, and 1794-TBN. The keyswitch must be set to position 4.

Q2: What is the resolution of the 1794-OE4 for voltage outputs?
A: The 1794-OE4 provides voltage resolution of 2.56 mV per count. Therefore, you achieve precise analog control for most applications.

Q3: Does the 1794-OE4 require regular calibration?
A: No, the 1794-OE4 does not require calibration. Consequently, maintenance costs and downtime are reduced significantly.

Q4: Can I use the 1794-OE4 with a MicroLogix controller?
A: Yes, the 1794-OE4 works with MicroLogix controllers. You need a 1794-ASB or 1794-APB communication adapter for connectivity.

Q5: What is the maximum conversion rate of the 1794-OE4?
A: The 1794-OE4 has a maximum conversion rate of 1.024 ms for all channels. Therefore, it responds quickly to control program changes.