The AI895 is a ABB Analog Input Module ,can directly interface 2-wire transmitters and with a particular connection it can also interface 4-wire transmitters without losing the HART capability. The design of the AI895 module fully considers the practical needs of industrial field applications. Its core features and advantages are reflected in the following aspects:
Integrated Intrinsic Safety (I.S.)
Built-in Protection: Each channel incorporates intrinsic safety protection components, allowing direct connection to process equipment (e.g., transmitters) installed in hazardous areas (such as ATEX/IECEx Zone 0/1) without the need for additional external safety barriers or isolators. This greatly simplifies system design, reduces cabinet space requirements, and lowers installation and material costs.
Extensive Certifications: The module complies with international explosion-proof standards such as ATEX and IECEx. It is suitable for harsh environments like Zone 2 with interfaces to Zone 0/1, ensuring safe operation in the presence of flammable gases or dust.
HART Communication Capability
Dual-Protocol Integration: While transmitting standard 4-20mA analog signals, the module supports superimposed HART digital communication signals. Users can access intelligent field devices (e.g., transmitters, actuators) via the HART protocol for parameter configuration, advanced diagnostics, status queries, and device information reading, enabling predictive maintenance.
DTM Support: Within the FDT/DTM framework of System 800xA, the AI895 module's DTM (Device Type Manager) features HART routing functionality. This allows host software (e.g., Fieldbus Builder) to communicate with HART instrument DTMs connected to its channels via this module, enabling centralized configuration and management of smart devices.
High Integration and Flexibility
8-Channel Density: A single module provides 8 independent analog input channels, optimizing rack space utilization, making it particularly suitable for high-density signal acquisition applications.
Flexible Power Supply Capability: Each channel can supply loop power (typically ≥15V @ 20mA) to connected two-wire transmitters and is capable of driving Ex-certified devices. Its low input voltage drop (typically 3V, including PTC) ensures sufficient operating voltage for field instruments.
Comprehensive Signal Processing: Supports various filter settings for noise suppression. Features high Common Mode Rejection Ratio (CMRR >80 dB) and Normal Mode Rejection Ratio (NMRR >10 dB), ensuring measurement accuracy in harsh electrical environments.
Powerful Diagnostics and Maintenance Features
Multi-Level Diagnostics: Provides module-level and channel-level diagnostics for quick fault localization, such as module missing, type error, external power failure, channel short/open circuit, etc.
HART Device Monitoring: The module monitors the communication status of connected HART instruments, scans for device presence, reports device-specific status (e.g., configuration changed, output fixed, out of limits), and displays this information clearly through the DTM interface.
Easy Maintenance: Supports hot-swapping (under system-permitted conditions). LED indicators on the module front provide intuitive Run, Fault, Warning, and HART communication status.
Seamless System Integration
Plug-and-Play: Compatible with the S800 I/O system and compact Measurement Terminal Units (MTUs) like TU890/TU891, enabling quick and simple two-wire connections.
Unified Engineering Environment: Within System 800xA, configuration, monitoring, and diagnostics are performed via its dedicated DTM, offering a consistent engineering and operational experience with the entire 800xA system, including user role management, online observation, parameter download, etc.
2. Detailed Technical Characteristics
1. Signal Acquisition and Processing
The AI895 is optimized for the industrial-standard 4-20mA current signal. Its 12-bit resolution provides sufficient accuracy for the vast majority of process monitoring applications, such as pressure, temperature, flow, and level measurement. The module's internal high-precision analog-to-digital converter and stable reference voltage ensure measurement consistency across a wide temperature range (temperature drift only 100 ppm/°C). Users can independently configure the filter time constant for each channel via the DTM to achieve the optimal balance between response speed and noise suppression.
2. Intrinsic Safety Design
The core safety feature of the AI895 lies in its "energy-limiting" design. The module's internal circuits are specially designed to ensure that, even under fault conditions, the electrical energy transmitted to the hazardous area is low enough to be incapable of igniting a specific explosive gas mixture. This allows it to be installed directly in the safe area (e.g., control cabinet) while extending signal lines to field instruments in the hazardous area, forming a complete and cost-effective intrinsically safe loop solution without intermediate safety barriers.
3. HART Protocol Integration
As a HART gateway, the AI895 manages the physical layer communication with field HART instruments. Its DTM provides rich HART-related functions:
Parameterization: Allows setting HART communication parameters, such as number of retries for busy/error responses, to optimize communication reliability.
Diagnostics: A dedicated "HART device" diagnostic tab displays device status (e.g., operations in progress, hardware faults), the HART instrument scan status for all channels (scan enabled, searching, disappeared, appeared, mismatched), and detailed communication error, command response, and field device status codes.
Service Functions:
Perform Master Reset: When new HART instruments are added or replaced in the field, executing this command forces the module to rescan all channels and update its internal HART device list.
Enable/Disable Scan: Controls whether the module periodically polls recognized HART devices to monitor their online status.
Read Gateway Parameters: Retrieves information such as the number of instruments recognized, scan status, retry settings, etc.
Perform Device Self-Test: Executes a self-test of the module's internal HART functionality.
4. Configuration and Operation
Configuration of the AI895 module is primarily done through its DTM within the System 800xA engineering environment (e.g., Control Builder or Fieldbus Builder). Key configuration interfaces include:
Channel Parameters: Each channel can be individually enabled/disabled. Signal range (fixed as 4-20mA), linearization (e.g., None, Square Root), and filter time can be selected.
Parameterization: Dedicated to configuring HART communication parameters.
Observe: Displays real-time measured values (digital, percentage, and bar graph) and channel status for all channels in online mode.
Service: Executes the advanced HART-related commands and functions mentioned above.
User roles and permissions (e.g., Observer, Operator, Maintenance, Planning Engineer) are integrated into the DTM applications, ensuring operational security.
3. Application Fields
The ABB AI895 Analog Input Module is widely used in industries requiring intrinsic safety protection, high-precision measurement, and intelligent device management, including:
Oil & Gas: Pressure, temperature, and flow monitoring on offshore platforms, refineries, and pipelines.
Chemical & Pharmaceutical: Process parameter monitoring for reactors, storage tanks, and production lines, complying with strict explosion-proof requirements.
Power Generation: Auxiliary process monitoring in power plants (especially coal-fired and gas-fired).
Metals & Mining: Production process monitoring in environments with explosive dust.
Water & Wastewater Treatment: Key parameter acquisition for pumping stations and treatment basins.
Any application using System 800xA that requires connection to intrinsically safe smart transmitters.
