Yokogawa AET Series Terminal Boards

Technical Dossier

Product Details And Specifications

Yokogawa AET Series Terminal Boards Technical Notes

The Yokogawa AET series terminal boards are field-wiring interface components designed for use within Yokogawa's CENTUM CS, CENTUM CS 3000, and CENTUM VP distributed control systems — platforms that collectively represent decades of installed base across global heavy industry. These terminal boards serve as the physical connection layer between field instrumentation (sensors, actuators, transmitters) and the corresponding I/O modules housed in the control station. Their role is structural: without a correctly matched terminal board, the I/O module cannot interface with field wiring.

In petrochemical complexes, nuclear power facilities, LNG terminals, and continuous-process refineries, CENTUM-based control systems routinely operate for 20–30 years without full platform migration. The AET series terminal boards — though no longer in active production — remain critical maintenance components for these long-lifecycle installations. A single failed or missing terminal board can render an entire I/O slot inoperable, forcing either costly emergency sourcing or unplanned process interruption.

DriveKNMS reviews sourcing options for this model through RFQ handling before quotation.

The Evolution of AET Series Architecture

The AET terminal board series was developed in parallel with Yokogawa's CENTUM CS and CENTUM CS 3000 I/O subsystem architecture, which introduced a modular, rack-based field station design in the 1990s. Each terminal board is mechanically and electrically matched to a specific I/O module type — the pairing is not interchangeable across module families.

Early CENTUM CS installations used terminal boards with screw-type field wiring terminations. As the platform evolved into CENTUM CS 3000 and later CENTUM VP, Yokogawa introduced enhanced terminal board variants with improved surge protection, higher channel density, and support for HART pass-through communication. However, the physical form factor and backplane connector pinout were maintained across generations to preserve backward compatibility within the same field station chassis.

The AET4D specifically is a relay-type terminal board, designed to interface with digital output modules where relay contact isolation is required between the control system and field devices. This is a common requirement in safety-instrumented and high-voltage switching applications. Relay terminal boards of this type are among the most frequently replaced components in aging CENTUM installations due to contact wear over extended operational cycles.

AET Series Full Catalog & Functionalities (SKU List)

The following models represent the documented AET series terminal board range, classified by output/input type and application. All models are designed for use with Yokogawa CENTUM CS / CS 3000 field control stations.

Relay Output Terminal Boards

• AET4D: 4-channel relay output terminal board; contact isolation for digital output modules; suited for high-voltage field switching applications.
• AET8D: 8-channel relay output terminal board; higher channel density variant for relay DO applications in the same chassis slot.
• AET16D: 16-channel relay output terminal board; used where maximum relay channel count per slot is required.

Analog Input Terminal Boards

• AET4A: 4-channel analog input terminal board; pairs with AI modules for 4–20 mA or voltage signal termination.
• AET8A: 8-channel analog input terminal board; standard density AI termination for process variable inputs.
• AET16A: 16-channel analog input terminal board; high-density AI termination; common in large-scale process I/O marshalling.
• AET4AH: 4-channel analog input terminal board with HART pass-through support; enables HART device communication without additional multiplexers.
• AET8AH: 8-channel analog input terminal board with HART pass-through; standard density HART-capable AI termination.

Analog Output Terminal Boards

• AET4B: 4-channel analog output terminal board; interfaces with AO modules for 4–20 mA control signal output to field actuators.
• AET8B: 8-channel analog output terminal board; higher density AO termination for valve positioner and actuator control loops.

Digital Input Terminal Boards

• AET16DI: 16-channel digital input terminal board; dry contact or voltage-level DI signal termination.
• AET32DI: 32-channel digital input terminal board; high-density DI termination for status monitoring and interlock input applications.

Digital Output Terminal Boards

• AET16DO: 16-channel digital output terminal board; transistor-type DO termination for solenoid valve and indicator control.
• AET32DO: 32-channel digital output terminal board; high-density DO termination for large discrete output marshalling.

Thermocouple / RTD Input Terminal Boards

• AET4TC: 4-channel thermocouple input terminal board; cold junction compensation integrated; pairs with TC input modules.
• AET8TC: 8-channel thermocouple input terminal board; standard density TC termination for temperature measurement loops.

Sourcing Hard-to-Find & Obsolete AET Series Parts

The AET series terminal boards are no longer available through Yokogawa's standard distribution network. Facilities requiring replacement units face a constrained secondary market where counterfeit and misrepresented parts are a documented risk.

DriveKNMS sources AET series terminal boards exclusively from decommissioned Yokogawa CENTUM CS and CS 3000 field stations. Each unit undergoes physical inspection, connector integrity verification, and relay contact resistance testing (for relay-type boards) before being catalogued. Units that do not pass inspection are not listed for sale.

Facilities planning a phased migration to CENTUM VP should note that AET series terminal boards are not compatible with CENTUM VP I/O modules. Migration planning must account for full terminal board replacement as part of the I/O subsystem upgrade scope.

Quality Control for the AET Series Range

Terminal boards present specific inspection challenges that differ from active electronic modules. The AET series QC process at DriveKNMS addresses the failure modes most commonly observed in long-service terminal boards:

• Connector pin inspection: Backplane connectors are examined under magnification for pin deformation, oxidation, and contamination. Pins showing corrosion are cleaned and re-tested for contact resistance; boards with deformed pins are rejected.
• Relay contact resistance measurement: For relay-type boards (including AET4D), each relay contact is tested for closed-state resistance. Contacts exceeding 100 mΩ are flagged; boards with worn contacts are not listed as serviceable.
• Screw terminal torque and continuity check: Field wiring terminals are tested for mechanical integrity and electrical continuity. Stripped or high-resistance terminals are identified and documented.
• Surge protection component inspection: Where fitted, transient voltage suppression components are verified for integrity. Failed TVS components are a common cause of AI terminal board degradation in field environments with poor earthing.
• Physical label and revision verification: Yokogawa revision markings are cross-referenced against known production records to confirm model identity and hardware revision level.