Features and benefits

• Intrinsic safety applications – use with AI890. AI893. AI895. AO890. AO895. DI890 and DO890

• Compact installations of I/O modules

• Field signals and process power connections

• Connections to ModuleBus and I/O modules

• Mechanical keying prevents insertion of the wrong module

• Latching device to DIN rail

• DIN rail mounting

The TU891 is a compact MTU for the S800 I/O. The MTU is a passive

unit used for connection of the field wiring and power supply to

the I/O modules. It also contains a part of the ModuleBus. The

TU891 MTU has gray terminals for field signals and process voltage

connections. The maximum rated voltage is 50 V and maximum

rated current is 2 A per channel, but these are primarily constrained

to specific values by the design of the I/O modules for their

certified application.

The MTU distributes the ModuleBus to the I/O module and to the

next MTU. It also generates the correct address to the I/O module

by shifting the outgoing position signals to the next MTU.