ABB

Main Functions

Field discrete status signal acquisition: Receives dry‑contact or potential‑free on‑off signals from field switches, limit switches, relay auxiliary contacts and alarm contacts. It converts field‑side hardware status into digital logic signals recognizable by the INFI‑90 back‑plane bus.
Contact‑based galvanic isolation: Implements electrical separation between field‑wired circuits and DCS internal logic circuits via built‑in relay‑coupling isolation. It blocks ground‑loop interference, common‑mode noise and transient surge feedback from field wiring, protecting DCS controller and back‑plane circuits.More products: www.plcva.com

RS 851 Relay‑Isolated Discrete Input Module

Multi‑channel independent signal sampling: Provides multiple isolated discrete input channels. Each channel works independently without cross‑interference, detecting open‑circuit and closed‑contact states of field devices.
Front‑panel LED status indication: Equipped with LED indicator lights for each channel. LEDs reflect real‑time on‑off status of field input points, facilitating on‑site commissioning, troubleshooting and point‑check work.
Signal filtering and debounce processing: Built‑in hardware filtering circuit suppresses contact bounce and high‑frequency industrial electromagnetic interference, avoiding false status triggering caused by field‑contact jitter.
Logic‑level signal forwarding: Transmits stable discrete state data to INFI‑90 controller for interlock logic, sequence control, alarm judgement and sequence‑of‑event recording.

RS 851 Relay‑Isolated Discrete Input Module

Legacy INFI‑90 DCS cabinet deployment: Installed in standard INFI‑90 racks, acting as discrete input interface between field switching devices and DCS controller.
Field‑device status monitoring: Collects feedback signals from limit switches, valve position feedback contacts, motor running/stop auxiliary relays, local push‑buttons and alarm trip contacts.
Safety interlock and protection‑logic signal collection: Gathers hard‑wired interlock signals, emergency‑trip feedback and protection‑action status for thermal‑power, chemical, metallurgical and pulp‑and‑paper plants.

RS 851 Relay‑Isolated Discrete Input Module

Cross‑system dry‑contact signal interconnection: Receives potential‑free relay status signals from external PLC, safety systems and local control panels for system‑to‑system logic handshaking.
Plant maintenance, spare‑part replacement and retrofitting: Serves as critical spare replacement component for aging INFI‑90 control racks, used for equipment overhaul, field repair and legacy‑system modernization projects.
Sequence‑of‑event and batch‑process monitoring: Supplies discrete status data for equipment‑sequence monitoring, fault‑alarm triggering and batch‑production logic judgement.