RKC FB900 Modules: FB900 8N-4*4NN5/A1-F801/Y

Technical Dossier

Product Details And Specifications

RKC FB900 Series: Comprehensive Module Range and Technical Overview

The RKC FB900 is a modular, multi-loop temperature and process controller platform manufactured by RKC Instrument Inc. (Japan). It is deployed across continuous-process heavy industries including petrochemical refineries, nuclear facility auxiliary systems, pharmaceutical batch reactors, and steel mill heat treatment lines. The FB900 architecture supports up to 8 control loops per base unit, with distributed I/O expansion via dedicated module slots. Its long production lifecycle — spanning from the early 2000s through current active manufacture — has resulted in a substantial installed base globally, making spare parts availability a critical operational concern for plant maintenance engineers.

The Evolution of FB900 Architecture

The FB900 platform was introduced by RKC Instrument as a successor to the CB/CD series single-loop controllers, addressing the demand for centralized multi-loop management in process industries. The first-generation FB900 units featured analog input modules with fixed thermocouple/RTD ranges and relay output configurations. Subsequent hardware revisions introduced universal input modules capable of accepting TC, RTD, voltage, and current signals within a single slot — eliminating the need for dedicated input-type modules per loop.

Communication architecture evolved from proprietary RS-485 RKC protocol (SRZ) to support Modbus RTU/ASCII, enabling integration with third-party SCADA and DCS platforms without protocol converters. Later firmware revisions added Ethernet/IP and PROFIBUS-DP adapter compatibility via external communication modules. The FB900's backplane bus uses a proprietary high-speed serial interface; cross-generation module compatibility is slot-position and firmware-version dependent, and engineers must verify compatibility matrices before substituting modules across hardware revisions. Units manufactured before 2010 may require firmware upgrades to accept current-production I/O modules.

FB900 Full Catalog & Functionalities (SKU List)

The following SKUs represent verified, commonly stocked components within the RKC FB900 series, classified by functional category:

Base Controllers / CPU Units

FB900-8N: 8-loop base controller unit, standard I/O configuration
FB900-4N: 4-loop base controller, compact process applications
FB900-8N-4*4NN5/A1-F801/Y: 8-loop controller, 4×universal input / 4×relay output, RS-485 comm, pressure gauge variant — the primary SKU of this listing
FB900-8N-4*4NN5/A1: 8-loop controller, 4×universal input / 4×relay output, standard RS-485
FB900-4N-4*4NN5/A1: 4-loop controller, 4×universal input / 4×relay output

Input Modules (Analog / Universal)

FB900-UI4: 4-channel universal analog input module (TC/RTD/V/mA)
FB900-UI8: 8-channel universal analog input module, high-density rack
FB900-TC4: 4-channel dedicated thermocouple input module
FB900-RTD4: 4-channel Pt100 RTD input module
FB900-AI4-V: 4-channel voltage analog input, 0–10 V DC range

Output Modules

FB900-RO4: 4-channel relay output module, 250 VAC / 3 A per channel
FB900-AO4: 4-channel analog output module, 4–20 mA DC
FB900-SSR4: 4-channel SSR drive output module, 12 VDC pulse
FB900-DO4: 4-channel open-collector digital output module

Communication & Power Modules

FB900-COM-RS485: RS-485 communication adapter, Modbus RTU/RKC SRZ protocol
FB900-COM-ETH: Ethernet communication module, Modbus TCP
FB900-PSU-24: 24 VDC auxiliary power supply module for I/O bus
FB900-COM-PB: PROFIBUS-DP communication adapter module

Sourcing Hard-to-Find & Obsolete FB900 Parts

Several first- and second-generation FB900 modules have been discontinued by RKC Instrument, with end-of-life notices issued between 2015 and 2022. DriveKNMS maintains a dedicated inventory of new-old-stock (NOS), refurbished, and tested-used FB900 components to support plants operating legacy installations where full system replacement is not economically viable.

DriveKNMS sources FB900 modules through authorized surplus channels and direct procurement from decommissioned plant inventories. All units are inspected, functionally tested, and cataloged with firmware version and hardware revision data prior to listing. For obsolete communication modules and legacy relay output boards, DriveKNMS provides cross-reference documentation to identify compatible current-production alternatives where direct replacements are unavailable. Customers requiring long-term maintenance agreements (LTMAs) for FB900-based systems are supported with multi-year supply commitments and priority allocation from reserved stock.

Quality Control for the FB900 Range

The FB900's modular backplane architecture requires functional validation at both the module level and the integrated system level. DriveKNMS applies the following test protocol to all FB900 units processed through its facility:

Each base controller unit undergoes power-on self-test (POST) verification, loop configuration upload, and setpoint tracking accuracy measurement across the full input range. Input modules are tested with calibrated signal sources (TC simulation, RTD decade box, precision voltage/current source) to verify channel accuracy within RKC-specified tolerances (±0.1% FS typical). Output modules are load-tested at rated current/voltage to confirm relay contact integrity and analog output linearity. Communication modules are validated for Modbus RTU register map compliance using protocol analyzer equipment. Backplane bus integrity is verified by confirming error-free data exchange between all populated module slots under simulated process load conditions. Units exhibiting intermittent faults, degraded analog accuracy, or communication timeouts are quarantined and not released for sale.