Description

The ABB TBU850-A is a high-performance Termination Base Unit engineered for the ABB S800 I/O system. It serves as the physical and electrical interface between field sensors (such as thermocouples, mV sources, and potentiometers) and the S800 analog input modules (e.g., AI810. AI815). The TBU850-A provides essential signal conditioning functions, including galvanic isolation, cold junction compensation (CJC) for thermocouples, and linearization. By isolating the field side from the system side, it prevents ground loops, suppresses electromagnetic interference (EMI), and protects the sensitive DCS electronics from high-voltage transients. This module is indispensable for applications requiring precise temperature monitoring, such as motor bearing surveillance in drive systems, reactor temperature control, and turbine exhaust monitoring.

Application Scenarios

A petrochemical refinery using an ABB 800xA system to monitor a critical catalytic cracker experienced erratic temperature readings from multiple thermocouples installed on reactor vessels. The fluctuations were causing the safety system to initiate unnecessary shutdowns. Investigation revealed that large variable frequency drives (VFDs) operating nearby were injecting significant electrical noise into the sensor wiring, and ground potential differences were corrupting the low-level mV signals. The engineering team replaced the standard terminal blocks with ABB TBU850-A termination bases. The TBU850-A’s built-in galvanic isolation effectively broke the ground loops and filtered out the VFD-induced noise. The temperature readings stabilized immediately, eliminating false trips and allowing the refinery to operate at full capacity with confidence in their safety instrumentation.