ABB AO845A-eA Analog Output Module

The ABB AO845A-eA (3BSE045584R2) is an 8‑channel analog output module for the ABB S800 I/O system, widely used in distributed control systems (DCS) and PLC applications. This module provides high‑precision 4‑20 mA current outputs for controlling valves, actuators, inverters, and other process devices. Each channel is individually configurable for output range (0‑20 mA or 4‑20 mA) and includes comprehensive diagnostics such as wire‑break detection and load monitoring.

The module features galvanic isolation between channels and the backplane, ensuring immunity to ground loops and transients. It is housed in a rugged metal enclosure and is designed for hot‑swapping, allowing replacement without system shutdown. The AO845A‑eA is compatible with ABB’s 800xA and System 800xI automation platforms, as well as third‑party controllers via PROFIBUS or Modbus.

Technical Specifications

• Model: AO845A-eA (3BSE045584R2)

• Number of channels: 8 (analog outputs, isolated)

• Output signal: 0‑20 mA or 4‑20 mA (configurable)

• Resolution: 12 bits (approx. 0.025% of full scale)

• Accuracy: ±0.1% of full scale (at 25°C), ±0.2% over temperature

• Load impedance: 0‑750 Ω (at 20 mA)

• Output protection: Short‑circuit and overcurrent (auto‑reset)

• Diagnostics: Wire‑break, over/under range, output fault

• Isolation: 1500 V (channel‑to‑bus)

• Power supply: 24 V DC (from backplane), 150 mA

• Operating temperature: -20°C to +70°C

• Dimensions: 120 x 45 x 100 mm (H x W x D)

• Certifications: CE, UL, RoHS

Key Features

• High‑density output: 8 channels in a single module, reducing rack space requirements.

• On‑board diagnostics: Each channel monitors load and voltage, sending alerts to the controller for predictive maintenance.

• Built‑in voltage regulator: Ensures stable current output regardless of supply variations.

• Easy configuration: Parameters (range, fail‑safe value) are set via the engineering software.

• Hot‑swap capability: Allows module exchange without powering down the system (with compatible backplane).

Typical Applications

• Process control: Driving control valves, variable speed drives, and positioners in chemical, oil & gas, and power plants.

• Machine automation: Providing analog references to servo drives and hydraulic systems.

• Test and calibration: Generating precise current signals for sensor simulation.

• Building automation: Controlling dampers and actuators in HVAC systems.

Installation and Integration

Insert the module into a free slot in the S800 I/O rack. The module is automatically recognized by the fieldbus interface. Wiring is done via the front‑connector terminal blocks; use shielded twisted‑pair cables for each output. Connect the shield to the ground terminal. The module provides a status LED per channel for quick visual feedback. Configuration is performed in the control system’s engineering environment: assign the module to the appropriate control configuration, set the output range, and define the behavior on communication loss (hold last value or go to safe state).

Compliance

The AO845A‑eA complies with EN 61000‑6‑2/‑4, IEC 61131‑2, and carries CE and UL approvals. It is RoHS compliant and designed for pollution degree 2.

Conclusion

The ABB AO845A‑eA analog output module provides reliable, high‑precision signal generation for demanding process and machine control applications. Its diagnostics, isolation, and hot‑swap features enhance system availability and maintainability.