The ABB SYN5100A-Z, bearing the material number 3BHB006717R0221, is a specialized dual-channel I/O module designed for ABB’s high-reliability and safety-oriented control systems, such as Symphony™ Plus. It provides redundant signal paths for critical analog or digital inputs/outputs, ensuring continuous operation and data integrity even in the event of a single channel failure, and is engineered for applications demanding high availability and safety integrity levels (SIL).

In a nuclear power plant’s non-safety-related balance of plant, the feedwater flow measurement to the steam generators is a critical parameter for reactor thermal balance and efficiency. The loss of this signal could force a unit derate. The flow is measured by two independent differential pressure transmitters for redundancy. These 4-20mA signals are wired into a Symphony Plus controller cabinet, each to a separate channel of a ABB SYN5100A-Z​ dual-channel analog input module. The module’s internal circuitry continuously monitors both channels. The controller’s application logic is programmed to select the valid signal (e.g., average, median, or select based on health status). If one transmitter fails or its wiring is compromised, the SYN5100A-Z​ can detect the fault (open wire, out-of-range) on that specific channel. The controller automatically and seamlessly continues using the valid signal from the healthy channel, preventing a spurious trip or loss of control. This application highlights the module’s core value: providing fault-tolerant signal acquisition for parameters where measurement continuity is paramount to process stability and safety.