Product Overview

The ABB AO845, identified by part number 3BSE023676R1, is a high-performance analog output module designed for the S800 I/O system within Advant OCS and 800xA control architectures. This current amplifier circuit provides eight unipolar channels capable of driving 4-20mA signals with HART communication pass-through. Engineered for high-availability environments, the AO845 supports both individual and redundant configurations. In a redundant setup, two modules work in parallel, allowing for bumpless transition and continuous signal delivery even if one unit fails. The module is optimized for precision control of actuators, positioners, and variable speed drives where signal stability is a critical requirement for process safety.

Hardware Parameters and Technical Characteristics

The AO845 is built with 12-bit resolution and rigorous galvanic isolation to ensure accuracy and protection against industrial electrical interference.

• Model Identification AO845

• Order Number 3BSE023676R1

• Output Channels 8 unipolar, independently isolated channels

• Signal Range 4-20 mA (supports HART protocol)

• Resolution 12-bit

• Accuracy 0.1% of full scale

• Max Load Resistance 750 Ohms

• Isolation Rating 50V rated isolation

• Diagnostic Detection Open circuit (current deviation >1mA), low process voltage, short circuit, and transistor health

• Redundancy Support Compatible with dual-module redundant operation

• MTU Compatibility TU810, TU812, TU814, TU830, TU842, TU843

• Physical Specifications 1.22 kg; 24 x 19 x 5.3 cm

Industrial Applications and Operational Use Cases

This current amplifier module is essential for industries that prioritize uptime and precise field device regulation.

• Process Valve Actuation Controlling pneumatic and electric valve positioners in chemical plants and refineries, where redundant signal paths prevent unscheduled shutdowns.

• Variable Frequency Drive (VFD) Speed Control Providing accurate 4-20mA reference signals to high-power motor drives in water treatment and HVAC systems.

• HART Device Integration Facilitating remote calibration and diagnostic data retrieval from intelligent field instruments without disrupting the analog control signal.

• Emergency Shutdown (ESD) Support Utilizing internal error detection to monitor the health of the output circuit, ensuring that safety-critical actuators respond correctly to command changes.

• Distributed Control System (DCS) Expansion Serving as a scalable output interface for 800xA systems, allowing for high-density I/O clusters in compact control cabinets.