ABB AO895 3BSC690087R1 Analog Output Module | 8-Ch HART

Product Overview

The AO895 (Part ID: 3BSC690087R1) is a high-performance, 8-channel analog output module designed for the ABB 800xA and S800 I/O systems. This module provides unipolar, single-ended 4 to 20 mA signals to drive field actuators with 12-bit resolution precision. Engineered for hazardous area protection, it features integrated intrinsic safety components and individual HART interfaces for every channel. This allows for seamless digital communication and asset management of smart field devices while maintaining robust galvanic isolation from ground, ensuring stable control in demanding process industries like oil, gas, and chemicals.

Technical Configuration

The AO895 module is built to handle complex automation tasks with specific electrical and safety parameters:

• Channel Density: 8 unipolar single-ended channels, each supporting 4…20 mA signal ranges.
• HART Communication: Integrated HART pass-through on each individual channel for remote device configuration and diagnostics.
• Intrinsic Safety: Built-in safety barriers for direct connection to devices located in hazardous locations.
• Signal Range: Supports extended under/over-range detection from 2.5 mA to 22.4 mA to identify field faults.
• Isolation: Groupwise isolation from ground with a 500 V a.c. dielectric test voltage for superior noise immunity.

Technical Specifications

Installation Guide

Mount the AO895 on the appropriate ABB MTU (Module Termination Unit) designed for Intrinsic Safety. Ensure that the module is firmly clicked into place to establish a secure connection with the ModuleBus.

Field Wiring

Maintain strict separation between intrinsically safe and non-intrinsically safe wiring to comply with hazardous area regulations. Use shielded twisted-pair cables for 4-20 mA signals to minimize electromagnetic interference. Note that the 24V external power supply is critical for driving the output loops and must be fused according to ABB system guidelines.

Engineering Advantages

The AO895 excels in smart plant architectures by combining high-density output with full HART transparency. This eliminates the need for external HART multiplexers and separate safety barriers, significantly reducing cabinet space and wiring complexity. Its scalable 4-20 mA output allows for extremely precise valve positioning, while its groupwise isolation ensures that a ground fault on one loop does not jeopardize the integrity of the entire I/O rack.

Technical FAQs

Q1: Does this module require a separate intrinsic safety barrier?
A1: No. The AO895 features integrated safety components specifically designed for hazardous area protection, allowing for direct connection to IS-rated field devices.

Q2: Can I use HART communication on all 8 channels simultaneously?
A2: Yes. The AO895 provides an individual HART interface for each channel, enabling continuous communication with all connected smart devices.

Q3: What happens if the signal goes below 4 mA?
A3: The module supports an under-range down to 2.5 mA. If the signal drops below this threshold, the system typically triggers a "Short Circuit" or "Under-range" fault diagnostic.