Fisher Controls CL6821 Series Modules CL6821X1-A6 12P0663X032 Analog I/O Card

Technical Dossier

Product Details And Specifications

Fisher Controls CL6821 Series Technical Notes

The Fisher Controls (Emerson) CL6821 series represents a core family of analog I/O modules deployed within the Provox Distributed Control System (DCS) platform. Provox installations are deeply embedded across global heavy industry — including petrochemical refineries, nuclear power generation facilities, offshore platforms, and large-scale chemical processing plants. The CL6821 series specifically handles analog signal conditioning and I/O interfacing between field instrumentation and the Provox controller backbone. Due to the long operational lifecycles typical of DCS infrastructure (15–30+ years), CL6821 modules remain in active service at facilities that commissioned Provox systems in the 1980s and 1990s. Replacement demand is driven by component aging, board-level failures, and the absence of OEM production support.

CL6821 Full Catalog & Functionalities (SKU List)

The following SKUs represent verified members of the Fisher Controls CL6821 and closely related Provox analog I/O module family. Each entry reflects a distinct board assembly or revision used in Provox DCS card cage configurations:

CL6821X1-A6 12P0663X032: Analog I/O card, 12P0663X032 PCB rev, 4–20 mA multi-channel input/output interface module.
CL6821X1-A2: Analog input module, early revision, standard 4–20 mA signal range, single-ended configuration.
CL6821X1-A4: Analog I/O module, mid-series revision, enhanced noise filtering for refinery environments.
CL6821X1-A8: Analog output card, 8-channel configuration, loop-powered 4–20 mA transmitter interface.
CL6821X2-A2: Second-generation analog input module, improved isolation, compatible with Provox cage rev 3+.
CL6821X2-A4: Analog I/O, X2 board revision, dual-rail power supply compatibility, updated signal conditioning.
CL6821X2-A6: Analog I/O card, X2 PCB generation, 12-channel capable, enhanced EMI shielding.
CL6821X2-A8: Analog output module, X2 revision, 8-channel 4–20 mA output, DCS highway interface.
CL6823X1-A2: Related Provox analog input module, thermocouple/RTD signal conditioning variant.
CL6823X1-A4: Analog input, temperature measurement variant, multi-sensor input with cold junction compensation.
CL6824X1-A2: Analog output module, voltage output variant (1–5 V), used in valve positioner applications.
CL6824X1-A4: Analog output, 4–20 mA, high-drive current capability for long cable runs in field installations.
CL6825X1-A2: Pulse input module, frequency-to-analog conversion, flow meter interface for Provox DCS.
CL6826X1-A2: Analog I/O combination module, mixed input/output channel configuration, cage slot-efficient design.
CL6827X1-A2: High-density analog input module, 16-channel multiplexed input, used in large-loop count applications.
CL6828X1-A2: Analog output expander module, used in conjunction with CL6821 controllers for extended output capacity.