ABB AI895 3BSC690086R1 Analog Input Module S800

The ABB AI895 3BSC690086R1, also cataloged as the AI895 Analog Input Module, provides eight 4-20 mA input channels with HART communication for the ABB S800 I/O system. Each channel supports two-wire transmitters and includes intrinsic safety protection for interfacing with process equipment in hazardous areas. With a suitable connection, the module also supports four-wire transmitters while retaining HART capability. It is compatible with TU890, TU891, and TU891Z Module Termination Units (MTUs).

Hardware Specifications

Intrinsic Safety and HART Signal Processing

The AI895 integrates intrinsic safety protection components on each input channel. Each channel can supply and monitor a two-wire process transmitter while supporting HART communication over the current loop. The built-in current-limited transmitter supply provides at least 15 V at a 20 mA loop current, with overload current limited to 23 mA.

Four-wire transmitters can also be connected using a specified wiring arrangement that preserves HART functionality. The input stage has a typical voltage drop of 3 V, including the PTC component. Installation design must account for this voltage drop when checking transmitter voltage requirements and available loop power.

Frequently Asked Questions

Q: Can the AI895 interface with both two-wire and four-wire transmitters?

A: Yes. Two-wire transmitters are powered and monitored by the module. Four-wire transmitters can be connected using the specified connection arrangement while retaining HART communication capability.

Q: Which MTUs are compatible with the AI895?

A: The module is specified for use with TU890, TU891, and TU891Z MTUs. TU890 is intended for Ex applications, while TU891 is intended for non-Ex applications. Confirm the applicable MTU variant and installation certification before commissioning.

Q: Does the AI895 support redundant operation or hot swapping?

A: The supplied specifications identify the module as non-redundant. They do not establish a hot-swap capability. Check the applicable ABB S800 hardware and system documentation before removing or replacing the module in an energized system.

Field Installation Guidelines

• MTU selection: Verify the installed MTU type and its suitability for the intended hazardous-area application. Confirm compatibility with the system configuration before mounting the module.
• Mechanical installation: Install the module in the designated S800 I/O position and verify connector engagement, mounting security, and access to the front diagnostic LEDs.
• Transmitter wiring: Follow the ABB wiring diagram for each two-wire or four-wire transmitter arrangement. Check polarity, loop current requirements, and the voltage drop across the module before energizing the circuit.
• HART communication: Maintain the specified loop wiring arrangement and verify HART communication after commissioning. Use the Tx LED and system diagnostics as applicable.
• Hazardous-area installation: Observe the applicable intrinsic safety control drawings, entity parameters, grounding requirements, and hazardous-area certification conditions. Do not substitute a non-Ex MTU where an Ex-approved configuration is required.
• Grounding and shielding: Apply the manufacturer's grounding and cable-shield termination instructions. Keep analog signal wiring separated from high-voltage conductors and switching power cables to reduce electromagnetic interference.
• Power verification: Confirm the +5 V Modulebus and +24 V external supply requirements against the installed I/O system power budget. Check the external transmitter supply under the actual connected load.
• Environmental limits: Maintain the specified operating temperature and humidity limits. For vertical mounting with a compact MTU, observe the 40 deg C maximum ambient temperature stated in the supplied data.
• Commissioning checks: Verify channel configuration, 4-20 mA input response, transmitter supply voltage, HART communication, and Fault, Run, and Warning indications before placing the loop into service.