TU842 3BSE020850R1 ABB S800 I/O Redundant Module Termination Units

ABB TU842 3BSE020850R1 S800 I/O Redundant Module Termination Unit

The ABB TU842 3BSE020850R1, also cataloged as the TU842 Redundant Module Termination Unit, operates as a dedicated hardware component for dual-ModuleBus distribution and 16-channel signal termination within S800 I/O DCS platforms.

Hardware Specifications

Backplane Bus Communication Velocity & Backplane Addressing

The TU842 base unit splits and channels two independent ModuleBus signals directly to each installed I/O module while extending the communication lines onward to the next adjacent termination unit. Integrated address logic automatically shifts the outgoing position signals to generate precise module addresses along the cluster chain, which preserves deterministic data routing across the backplane without software configuration.

Frequently Asked Questions

Q: How does the TU842 establish hardware address assignments for attached S800 I/O modules?

A: Internal physical connections shift the position-encoding signals as ModuleBus lines pass through the base plate. The unit automatically generates a unique address for each attached I/O module and passes the incremented address signal to the next downstream termination unit.

Q: What prevents technicians from inserting an incorrect S800 I/O module type into the TU842?

A: Technicians set four mechanical keying pegs on the module base plate (two pegs per module position). These physical keys restrict slot access to match specific module types out of 36 selectable key combinations, which blocks incompatible hardware insertions.

Q: What are the maximum electrical limits for field wiring across individual terminal channels?

A: Each terminal channel supports a maximum operational rating of 50 V and carries up to 3 A per channel across its dual I/O and dedicated ZP connections.

Field Installation Guidelines

Technicians mount the TU842 base unit directly onto a standard 35 mm DIN rail. Ensure that the metallic DIN-rail latch snaps securely into position, because this physical connection establishes the primary protective grounding path for the base module. Install field conductors using standard 3-wire practices, routing signal pairs and process power connections into their designated terminal blocks. Configure the four mechanical keying wheels to match the assigned S800 I/O module profiles before plugging in active cards. To maintain system reliability, secure all field wiring trunks with strain reliefs and verify that signal cables maintain adequate separation from high-voltage AC lines.