ABB NKTU Series Modules: NKTU01-20

Technical Dossier

Product Details And Specifications

ABB NKTU Series: Comprehensive Module Range and Technical Overview

The ABB NKTU series is a family of I/O bus termination and communication interface modules developed for ABB's Advant Controller and AC800M distributed control system (DCS) platforms. These modules are deployed across global heavy industry sectors including petrochemical refineries, nuclear power stations, offshore oil & gas platforms, pulp and paper mills, and large-scale chemical processing facilities. The NKTU series functions as the physical and logical bridge between field instrumentation and the controller backplane, enabling deterministic, high-integrity signal transmission in safety-critical environments. Installed base counts for this series run into the tens of thousands of nodes globally, making long-term parts availability a primary operational concern for plant maintenance engineers.

The Evolution of NKTU Series Architecture

The NKTU series was introduced as part of ABB's Advant OCS (Open Control System) architecture in the early 1990s, designed to interface S100 and S800 I/O families with the Advant Controller 110, 160, and 450 platforms. Original NKTU01 variants used parallel backplane communication over ABB's proprietary S100 bus protocol. As ABB transitioned to the AC800M platform in the late 1990s and early 2000s, the NKTU series was extended to support Modulebus and PROFIBUS-DP communication layers, enabling coexistence with modern fieldbus architectures.

The -20 hardware revision suffix on the NKTU01-20 denotes improved EMC shielding and extended operating temperature tolerance compared to the original NKTU01-10. Subsequent revisions addressed firmware compatibility with AC800M controller versions 5.x and 6.x. As of 2026, the NKTU series has entered the mature/end-of-life phase of its product lifecycle. ABB has formally discontinued active volume production of most NKTU variants. For plants running legacy Advant installations, third-party lifecycle extension support and certified refurbished stock remain the primary sourcing channels.

NKTU Series Full Catalog & Functionalities (SKU List)

The following SKUs represent verified, commonly deployed modules within the ABB NKTU and closely associated Advant/AC800M I/O interface families, classified by functional category.

I/O Bus Termination Units (NKTU Core Series)

• NKTU01-10: S100 I/O bus termination unit, revision 10, original hardware release, single-channel
• NKTU01-20: S100 I/O bus termination unit, revision 20, improved EMC shielding, extended temp range
• NKTU02-20: Dual-channel I/O bus termination unit for redundant S100 backplane configurations
• NKTU03-20: Extended I/O bus termination unit with enhanced diagnostic LED array and fault isolation
• NKTU04-20: High-density bus termination unit, supports up to 12 I/O modules per rack segment

Analog Input (AI) Modules

• AI810: 8-channel analog input, 4–20 mA / 0–10 V, HART-capable, S800 I/O family
• AI820: 8-channel analog input with galvanic isolation per channel, 4–20 mA
• AI830A: 8-channel RTD/thermocouple analog input, multi-sensor type configurable
• AI835A: 8-channel HART analog input, loop-powered, SIL 2 rated per IEC 61508
• AI843: 4-channel high-accuracy analog input, ±0.05% full-scale accuracy, isolated

Analog Output (AO) Modules

• AO810V2: 8-channel analog output, 4–20 mA, HART-capable, hardware revision 2
• AO820: 8-channel analog output with individual channel galvanic isolation, 4–20 mA
• AO845A: 4-channel high-accuracy analog output, SIL 2 rated, redundancy-capable

Digital Input (DI) Modules

• DI810: 24-channel 24 VDC digital input, sink/source configurable, S800 I/O family
• DI820: 24-channel digital input, 120 VAC field voltage compatible
• DI830: 24-channel digital input with SOE (Sequence of Events) 1 ms timestamping
• DI840: 24-channel digital input, 24 VDC, SIL 2 rated, used in safety-instrumented systems

Digital Output (DO) Modules

• DO810: 24-channel 24 VDC digital output, 0.5 A per channel, transistor output
• DO820: 16-channel relay output module, 2 A per contact, AC/DC field voltage
• DO840: 24-channel digital output, SIL 2 rated, used in safety shutdown applications

CPU & Communication Modules

• PM864A: AC800M main processor module, 32 MB RAM, dual 10/100 Ethernet ports
• PM865A: AC800M high-performance processor, 64 MB RAM, hot-standby redundancy-capable
• CI854A: PROFIBUS-DP master/slave communication interface for AC800M rack
• CI856: INSUM communication interface module for MNS motor control center integration
• CI858: DeviceNet communication interface module for AC800M, master mode

Sourcing Hard-to-Find & Obsolete NKTU Series Parts

DriveKNMS maintains a dedicated inventory program for discontinued ABB Advant and AC800M components, with specific focus on NKTU series termination units. As ABB has ceased volume production of NKTU01-10, NKTU01-20, NKTU02-20, and NKTU03-20, the primary sourcing channels are decommissioned plant stock, certified refurbished units, and cross-regional surplus inventory. DriveKNMS operates a global procurement network that sources NKTU modules from plant shutdowns in Europe, North America, and Asia-Pacific. Each unit is subject to incoming inspection before entering available stock. Lead times for NKTU series modules typically range from 3 to 15 business days depending on revision and quantity. For large-quantity requirements or bill-of-materials sourcing across multiple NKTU variants, DriveKNMS provides consolidated quotation services to reduce procurement overhead for maintenance engineering teams.

Quality Control for the NKTU Series Range

NKTU series modules present specific test challenges due to their backplane bus interface architecture and multi-pin edge connector design. DriveKNMS applies the following quality control protocol to all NKTU units processed through its facility:

• Visual inspection of backplane connector pins for oxidation, mechanical deformation, and solder joint integrity
• Functional bus communication test using an ABB S100 I/O rack test fixture to verify Modulebus signal integrity at rated clock speeds
• Firmware version identification and documentation against known compatible AC800M controller firmware matrices
• Burn-in cycle: 48-hour powered operation at 40°C ambient to screen latent component failures
• Electrical isolation test between bus lines and chassis ground per IEC 61010-1 requirements
• Each unit ships with a test report documenting pass criteria, firmware version, and hardware revision code