Mitsubishi FX3U Series Modules: FX3U-4DA

Technical Dossier

Product Details And Specifications

Mitsubishi FX3U Series: Comprehensive Module Range and Technical Overview

The Mitsubishi Electric FX3U series is the third-generation flagship of the MELSEC FX compact PLC family. Deployed across petrochemical plants, automotive assembly lines, water treatment facilities, and discrete manufacturing operations worldwide, the FX3U platform established itself as the de facto standard for mid-range compact automation between 2004 and the mid-2010s. Its 32-bit RISC CPU architecture, high-speed pulse output capability (up to 100 kHz), and extensive special function module ecosystem made it the preferred controller for applications requiring precision motion, analog process control, and multi-axis coordination without the cost overhead of a full rack-based system.

In heavy industry segments — including refinery instrumentation, nuclear auxiliary systems, and chemical batch processing — FX3U controllers remain embedded in validated control loops where system re-qualification costs make platform migration economically prohibitive. The installed base of FX3U hardware in these sectors sustains long-term demand for both new and refurbished spare modules well beyond the product's official production lifecycle.

The Evolution of FX3U Architecture

The MELSEC FX series progressed through four distinct hardware generations, each introducing expanded I/O density, faster scan times, and broader communication options.

FX1S / FX1N (1990s–early 2000s): Entry-level compact PLCs with fixed I/O configurations and limited special function module support. Still found in legacy conveyor and packaging lines operating under long-term maintenance agreements.

FX2N (2000–2010): Introduced a modular extension block architecture and a broad library of analog, positioning, and communication modules. The FX2N remains one of the most widely installed compact PLCs globally and is now fully discontinued, creating sustained demand for spare parts.

FX3U / FX3UC / FX3G (2004–2018): The FX3U introduced a 32-bit CPU, USB programming port, built-in high-speed counters (up to 6 axes at 100 kHz), and native CC-Link and PROFIBUS connectivity via adapter modules. The FX3UC variant offered a compact connector-type terminal for space-constrained panel installations. The FX3G provided a cost-reduced alternative with reduced I/O expansion capacity.

FX5U (2015–present): Current-generation platform with built-in Ethernet, iQ Works engineering environment compatibility, and structured text programming support. Mitsubishi positions the FX5U as the migration target for FX3U applications; however, direct hardware substitution is not possible without engineering rework, re-wiring, and in regulated industries, full system re-validation.

For facilities operating validated FX3U-based control systems, the cost of migrating to FX5U — including re-engineering, re-validation, and production downtime — routinely exceeds the cost of maintaining a strategic spare parts inventory for the existing platform by a factor of 10 to 50. Sourcing FX3U modules from specialist distributors is the operationally rational choice for asset life extension of 5 to 10 years.

FX3U Full Catalog & Functionalities (SKU List)

CPU & Base Units

FX3U-16MR/ES: 8 DI / 8 DO relay output base unit, 16 I/O, AC power supply
FX3U-32MR/ES: 16 DI / 16 DO relay output base unit, 32 I/O, AC power supply
FX3U-48MR/ES: 24 DI / 24 DO relay output base unit, 48 I/O, AC power supply
FX3U-64MR/ES: 32 DI / 32 DO relay output base unit, 64 I/O, AC power supply
FX3U-80MR/ES: 40 DI / 40 DO relay output base unit, 80 I/O, AC power supply
FX3U-128MR/ES: 64 DI / 64 DO relay output base unit, maximum I/O density configuration
FX3U-32MT/ES: 16 DI / 16 DO transistor sink output, high-speed pulse output capable, AC power
FX3U-64MT/ES: 32 DI / 32 DO transistor sink output, high-speed pulse, AC power supply

Analog Output Modules

FX3U-4DA: 4-channel analog voltage/current output; ±10 V and 4–20 mA; 12-bit resolution; setpoint transmission and valve positioner control
FX3U-2DA: 2-channel analog output; compact footprint for space-constrained panel installations
FX3U-4DA-ADP: 4-channel analog output adapter; mounts to CPU left-side expansion port; does not consume right-side module slots

Analog Input Modules

FX3U-4AD: 4-channel analog voltage/current input; 12-bit resolution; ±10 V and 4–20 mA selectable per channel
FX3U-8AD: 8-channel analog input; higher channel density for multi-loop process monitoring applications
FX3U-4AD-ADP: 4-channel analog input adapter; left-side CPU port mount; preserves right-side expansion capacity
FX3U-4AD-PT-ADP: 4-channel PT100 RTD temperature input adapter; direct sensor connection
FX3U-4AD-TC-ADP: 4-channel thermocouple input adapter; supports K, J, T, E, R, S, B thermocouple types

Communication & Network Modules

FX3U-ENET: Ethernet communication module; 10/100BASE-TX; supports SLMP and MC protocol for SCADA integration
FX3U-232-BD: RS-232C communication board; mounts on CPU board expansion slot; supports non-protocol and MODBUS RTU
FX3U-485-BD: RS-485 communication board; MODBUS RTU master/slave; multi-drop network support
FX3U-USB-BD: USB programming communication board; replaces RS-422 programming cable requirement
FX3U-PROFIBUS-DP: PROFIBUS-DP slave adapter; integrates FX3U into Siemens S7 and ABB DCS environments
FX3U-64CCL: CC-Link remote device station module; 64-point I/O allocation; for Mitsubishi CC-Link network integration

Positioning & Motion Modules

FX3U-1PG: Single-axis pulse output positioning module; up to 1 MHz pulse output; open-collector and differential line driver output
FX3U-20SSC-H: 2-axis SSCNET III/H motion control module; interfaces with MR-J4 servo amplifiers; synchronous control capable

Power Supply & Extension Units

FX3U-1PSU-5V: Auxiliary 5 V DC power supply unit; extends available power budget for large special function module configurations
FX3U-CNV-BD: Conversion board; enables FX2N extension blocks to connect to FX3U CPU for legacy system expansion

Sourcing Hard-to-Find & Obsolete FX3U Parts

Mitsubishi Electric has officially transitioned the FX3U series to mature product status, with production of select models discontinued or subject to last-time-buy restrictions. For plant engineers and maintenance managers, this creates a procurement gap that standard distribution channels cannot reliably fill.

DriveKNMS maintains a dedicated inventory of FX3U modules sourced through authorized secondary market channels, including decommissioned equipment recovery, factory-sealed surplus, and professionally refurbished units. Our procurement network spans Asia-Pacific, European, and North American industrial surplus markets, enabling us to locate low-volume, high-specificity SKUs that tier-1 distributors no longer stock.

For facilities with multi-year maintenance contracts or planned shutdowns, we offer bulk reservation and long-term storage agreements, ensuring that critical spare modules are available on demand without exposure to spot-market price volatility.

Extending an FX3U-based system's operational life by 5 to 10 years through strategic spare parts management — rather than executing a full platform migration — typically reduces total cost of ownership by 60 to 80 percent when factoring in engineering labor, system re-validation, operator retraining, and production downtime.

Quality Control for the FX3U Range

FX3U special function modules communicate with the CPU via a dedicated high-speed parallel bus. Degradation in bus interface circuitry, connector pin integrity, or onboard firmware can produce intermittent faults that are difficult to diagnose in the field. Our QC process for FX3U modules addresses these failure modes systematically.

Step 1 – Visual and Mechanical Inspection: Full examination of PCB surface, connector pins, and housing for corrosion, mechanical damage, or evidence of thermal stress. Electrolytic capacitors are inspected for bulging or electrolyte leakage — a primary failure mode in modules aged 10 or more years.

Step 2 – Firmware Version Verification: Module firmware version is read and logged. Where applicable, firmware is compared against Mitsubishi's published version history to confirm compatibility with target CPU firmware revisions.

Step 3 – Bus Communication Test: Module is installed in a reference FX3U base unit and FROM/TO instruction communication is verified across all buffer memory registers. Error flags and WDT behavior are monitored under simulated load conditions.

Step 4 – Channel-Level Functional Test: For analog modules including the FX3U-4DA, each channel is tested across its full output range. Voltage output accuracy is verified at ±10 V full scale; current output linearity is confirmed across the 4–20 mA range using calibrated reference instruments traceable to national standards.

Step 5 – Burn-In and Final Documentation: Modules are powered continuously for a minimum of 24 hours under operational load. A test report documenting all measured parameters is issued with each unit shipped.