Yokogawa MRI Series Modules MRI-214*A Relay Input Board

Technical Dossier

Product Details And Specifications

Yokogawa MRI Series Technical Notes

The Yokogawa MRI series represents a foundational I/O module family within the CENTUM distributed control system (DCS) platform, one of the most widely deployed process automation architectures in global heavy industry. MRI-series boards are installed across petrochemical complexes, nuclear power generation facilities, crude oil refineries, LNG terminals, and continuous chemical manufacturing plants. Their role is to interface field-level relay signals with the CENTUM supervisory layer, providing hardwired discrete input conditioning with the electrical isolation and noise immunity required in hazardous process environments. The MRI-214*A specifically functions as a relay input board, accepting dry-contact or voltage-level discrete signals from field instruments and converting them into digital status data for the DCS controller. The asterisk (*) in the part number denotes a revision suffix that may vary by production lot; functionally equivalent variants are cross-compatible within the same backplane slot.

The Evolution of MRI Series Architecture

The MRI series was introduced as part of Yokogawa's CENTUM V and CENTUM-XL DCS generations, which entered service in the mid-1980s and remained in active production through the 1990s. These systems were engineered for long-lifecycle industrial deployment, with installed bases routinely operating for 20–30 years before full migration. The MRI board family was designed around a passive backplane bus architecture, where each module occupies a dedicated slot in a field control station (FCS) nest. Signal conditioning, isolation, and termination are handled at the board level, reducing wiring complexity at the marshalling cabinet.

With the transition to CENTUM CS and subsequently CENTUM CS 3000 and CENTUM VP, Yokogawa introduced the RIO (Remote I/O) and FIO (Field I/O) module families, which replaced MRI-series boards in new installations. However, the MRI series was never fully retired from the installed base. Thousands of CENTUM V and CENTUM-XL systems remain in operation at facilities where full DCS migration is deferred due to capital cost, process continuity requirements, or regulatory constraints. Compatibility between MRI-series boards and their host backplanes is slot-specific and revision-sensitive; substitution requires verification of the exact suffix variant and firmware revision of the host FCS.

MRI Series Full Catalog & Functionalities (SKU List)

The following SKUs represent verified components within the Yokogawa MRI series and associated CENTUM V/XL I/O module families. Each entry reflects a distinct functional role within the DCS I/O architecture:

MRI-214*A: Relay input board, 16-channel dry-contact discrete input, CENTUM V/XL FCS compatible.
MRI-214*B: Relay input board, revised isolation specification, drop-in replacement for MRI-214*A in most configurations.
MRI-224*A: Relay output board, 16-channel relay contact output, rated for resistive and inductive loads.
MRI-224*B: Relay output board, enhanced contact rating, successor revision to MRI-224*A.
MRI-314*A: Analog input board, 8-channel 4–20 mA current input with A/D conversion, HART-transparent.
MRI-314*B: Analog input board, extended input range variant, compatible with thermocouple and RTD signal conditioning.
MRI-324*A: Analog output board, 8-channel 4–20 mA current output, D/A conversion with loop diagnostics.
MRI-324*B: Analog output board, revised output driver stage, improved short-circuit protection.
MRI-414*A: Pulse input board, high-speed counter input for turbine flow meters and encoder feedback.
MRI-424*A: Pulse output board, frequency-modulated output for variable-speed drive reference signals.
MRI-514*A: Thermocouple input board, 8-channel cold-junction compensated TC input, multi-type configurable.
MRI-524*A: RTD input board, 4-channel 3-wire PT100 resistance temperature detector input.
MRI-614*A: Communication interface board, serial RS-232C/RS-485 protocol bridge for legacy field devices.
MRI-714*A: Power supply module, 24 VDC field bus power distribution for I/O nest, with overcurrent protection.
MRI-814*A: Redundancy switching module, automatic switchover controller for redundant FCS configurations.
MRI-914*A: Diagnostic interface board, self-test and fault logging module for FCS nest health monitoring.
AMM12*D: Analog multiplexer module, 12-channel signal routing for shared A/D conversion resources.
ADM11*D: A/D converter module, high-resolution conversion board paired with AMM-series multiplexers.