Product Introduction
When hazardous area process signals demand reliable isolation and intrinsic safety without external barriers, the ABB AI895 Analog Input Module delivers a compact, integrated solution. Part of the ABB S800 I/O family, this 8-channel module directly interfaces 2-wire transmitters and, with a specific connection, also handles 4-wire transmitters while preserving HART communication capability. Each channel includes intrinsic safety protection components, enabling connection to equipment in Zone 0/Zone 2 hazardous locations without additional external devices.
Technical Specifications Breakdown
Channel Configuration and Signal Type
The AI895 provides 8 single-ended unipolar inputs for 4...20 mA current loops, arranged as one group of 8 channels isolated from ground. This groupwise isolation simplifies wiring and reduces common-mode noise issues in industrial environments.
HART Communication and Transmitter Power
Every channel supports HART communication, allowing simultaneous analog measurement and digital data exchange. The built-in transmitter supply delivers at least 15 V at 20 mA loop current to power Ex certified two-wire transmitters, with current limiting to 23 mA under overload conditions. The input voltage drop is typically 3 V, including the PTC protection.
Accuracy and Environmental Robustness
With a 12-bit resolution and a typical error of 0.05% (max 0.1%), the module ensures precise measurement. Temperature drift is typically 100 ppm/°C, and the input filter rise time (0-90%) is 20 ms. Common-mode rejection exceeds 80 dB at 50/60 Hz, while normal-mode rejection exceeds 10 dB. The rated insulation voltage is 50 V, with a dielectric test voltage of 500 V AC. Power dissipation is 4.75 W.
Industry Applications
Chemical and Petrochemical Plants
In environments where flammable gases or vapors are present, the AI895's intrinsic safety design eliminates the need for external safety barriers, reducing cabinet space and installation complexity. The module's ATEX/IECEx Zone 2 approval with interface to Zone 0 ensures compliance with stringent safety standards.
Oil and Gas Refineries
For monitoring pressure, temperature, and flow from 2-wire transmitters in hazardous areas, the AI895 provides reliable loop power and HART communication. The 8-channel density optimizes I/O count per module, lowering overall system cost.
Installation and Setup Guidance
Mount the AI895 on a TU890 or TU891 Compact MTU (Termination Unit). The TU890 is designed for Ex applications, while the TU891 suits non-Ex environments. The TU891Z is also compatible. Use the keying code AE to ensure correct insertion. The module measures 45 mm wide, 102 mm deep (111 mm including connector), and 119 mm high, weighing 0.2 kg. Ensure adequate airflow for cooling, as the maximum ambient temperature is 55 °C (131 °F) for horizontal mounting, or 40 °C (104 °F) for vertical mounting in a compact MTU.
Maintenance and Reliability
Routine inspection should focus on the front panel LEDs (Fault, Run, Warning, Tx for HART communication) to quickly identify channel or communication issues. The module supervises its internal process supply. Given the intrinsic safety circuits, do not attempt internal repairs; follow the manufacturer's safety manual for periodic testing. The module operates in 0 to +55 °C and stores at -40 to +70 °C, with 5 to 95% non-condensing humidity. Pollution degree 2 per IEC 60664-1 and corrosion protection per ISA-S71.04: G3 ensure long-term reliability in harsh industrial atmospheres.
Compatibility and Integration
The AI895 integrates seamlessly with ABB S800 I/O systems. Use with TU890, TU891, or TU891Z MTUs for termination. The module communicates via the Modulebus, consuming typically 130 mA from the +5 V Modulebus and typically 270 mA (max <370 mA) from the +24 V external supply. It is CE marked and complies with EN 61010-1, EN 61010-2-201 for electrical safety, and EN 61000-6-4, 61000-6-2 for EMC. Marine certifications include ABS, BV, DNV, and LR.
Selection Guide and Purchasing Advice
Before ordering, verify that your system supports the S800 I/O architecture and that the MTU (TU890 for Ex, TU891 for non-Ex) is available. The AI895 requires a +24 V external power supply. Check the environmental conditions against the specified operating temperature and humidity ranges. SpareTechPLC stocks the ABB AI895 (3BSC690086R1) and associated MTUs, ensuring fast delivery for your project needs.
Frequently Asked Questions
Q1: Can the AI895 power 4-wire transmitters?
Yes, with a particular connection, the module can interface 4-wire transmitters without losing HART capability, though the primary design is for 2-wire transmitters.
Q2: What is the maximum loop current the module can supply?
The transmitter supply is current-limited to 23 mA under overload conditions, with a typical 20 mA loop current providing at least 15 V.
Q3: Is the AI895 suitable for SIL-rated applications?
The provided data does not mention any SIL rating. For safety-critical applications, consult the manufacturer's documentation and verify suitability.
Q4: What MTU should I use for hazardous area installations?
Use the TU890 Compact MTU for Ex applications. The TU891 is for non-Ex environments.
Q5: Does the module support redundancy?
No, the AI895 does not support redundancy as per the specifications.
