Description
The Allen-Bradley 1794-OE4 is a 4-channel analog output module designed for the FLEX I/O distributed automation platform. It converts 12-bit digital values from a network adapter (such as EtherNet/IP, ControlNet, or PROFIBUS adapters) into isolated analog current (4 to 20 mA) or voltage (\pm 10 V, 0 to 10 V) signals. These outputs drive field-level actuators, positioning valves, control dampers, and variable frequency drive (VFD) speed references.
Commercial Availability & Terms
- Condition: New Original (Factory Sealed), New Surplus, or Refurbished (Fully Bench Tested on automated test profiles) available.
- Warranty: 12-Month Functional Warranty across all product conditions.
- Lead Time: Typically ships from stock within 1 to 2 business days.
- Pricing Note: List pricing fluctuates based on supply dynamics and product series updates (Series A vs. Series B). Contact our industrial procurement desk for a firm, formal quote.
Technical Specifications
The following electrical and environmental specifications define the operational limits of the 1794-OE4 module.
| Parameter | Value |
| Manufacturer | Rockwell Automation / Allen-Bradley |
| Module Type | FLEX I/O Analog Output Module |
| Catalog Number | 1794-OE4 |
| Number of Channels | 4 Analog Outputs (single-ended) |
| Output Current Ranges | 4 to 20 mA, 0 to 20 mA (Configurable) |
| Output Voltage Ranges | \pm 10 V, 0 to 10 V (Configurable) |
| Digital Resolution | 12-bit binary (all ranges)
• Voltage: 2.56 mV/count • Current: 5.13 \muA/count |
| Data Format | Left-justified, 2’s complement or binary |
| External Power Input | 24 V DC Nominal (20.4 to 31.2 V DC range) |
| FlexBus Current Draw | 20 mA maximum at 5 V DC |
| Isolation Voltage | Channel-to-system: 850 V DC for 1 second
Channel-to-channel: None |
| Maximum Output Load | • Current loop: 750\ \Omega at 24 V DC
• Voltage loop: \ge 1000\ \Omega resistive |
| Compatible Terminal Bases | 1794-TB2, 1794-TB3, 1794-TB3S, 1794-TBN |
| Operating Temperature | 0 to +55^\circC (+32 to +131^\circF) |
Field Integration & Terminal Mapping
1. Terminal Base Wiring Layout
The 1794-OE4 requires a separate terminal base unit (e.g., 1794-TB3) for direct field wire landings. Analog output signals and their specific returns are assigned sequentially across the base rows. External 24 V DC loop power must be wired to designated terminals to energize the internal digital-to-analog converter (DAC) drive circuits.
2. Configuration Profiles and Scaling
Output ranges are established via the configuration registers inside the controller’s programming environment (RSLogix 5000 / Studio 5000 Logix Designer). The output channels map to specific words in the module’s output image array. If the external 24 V DC auxiliary supply drops below the lower operating threshold (20.4 V DC), a bit is pulled in the module input status register indicating a “power low” fault condition.
3. Noise Mitigation Rules
Because this module is single-ended (sharing a common internal analog return), ground loops can distort target signal metrics.
- Utilize shielded twisted-pair cables for all analog runs.
- Ground the cable shield at the terminal base chassis ground bar only.
- Maintain physical separation between analog signal conductors and high-voltage AC motor control lines to avoid electromagnetic interference.
System Constraint: The 1794-OE4 does not support hot-swapping (“Removal and Insertion Under Power” or RIUP) if installed on older legacy terminal bases or if the process environment poses an explosive hazard. Disconnect all field-side power before servicing the hardware card.
Frequently Asked Questions
Can I mix voltage and current outputs on the same 1794-OE4 module?
Yes. Each channel can be configured independently via the controller software profile. For instance, Channel 0 can be mapped for a 4 to 20 mA output to drive a valve positioner, while Channel 1 can output 0 to 10 V to command a fan motor drive reference.
What is the mechanical difference between the Series A and Series B versions?
Series B modules include updated internal electronic components to manage component obsolescence and offer improved immunity against high-frequency electrical noise. Series B units are fully backwards compatible with existing Series A application slots and utilize identical terminal bases.
What causes an output channel to clip or lag its commanded target value?
The most common causes are a field load impedance exceeding the maximum 750\ \Omega specification on current loops, or a voltage drop in the external 24 V DC power input supply lines. Measure the voltage across the terminal base power inputs under full load conditions
