Yokogawa SC4AJ Series Conductivity Sensors: SC4AJ-S-AD-09

Technical Dossier

Product Details And Specifications

Yokogawa SC4AJ Series: Comprehensive Module Range and Technical Overview

The Yokogawa SC4AJ series represents a line of industrial conductivity sensors engineered for continuous, in-line liquid analysis in demanding process environments. These sensors are deployed across global heavy industries including petrochemical refineries, nuclear power plant cooling circuits, chemical manufacturing plants, pulp and paper mills, and pharmaceutical purified water systems. The SC4AJ series interfaces directly with Yokogawa's FLXA21 and FLXA202 liquid analyzers, as well as legacy ISC40G and ISC40S transmitters, making it a critical measurement component within distributed control system (DCS) architectures built on CENTUM VP, CENTUM CS 3000, and ProSafe-RS platforms.

The series covers a conductivity measurement range from ultra-pure water applications (0.055 µS/cm) through high-concentration electrolyte streams (up to 2000 mS/cm), with cell constants ranging from 0.01 cm⁻¹ to 50 cm⁻¹. Materials of construction include PEEK, PPS, titanium, and Hastelloy C-276 to accommodate corrosive media. The SC4AJ-S-AD-09 specifically is a submersion/insertion-type sensor with a standard cell constant configuration suited for mid-range conductivity measurement in process water and chemical dosing loops.

The Evolution of SC4AJ Architecture

Yokogawa's liquid analysis sensor portfolio evolved from the early SC series contacting conductivity electrodes introduced in the 1980s, which used two-electrode cells with limited compensation for polarization effects. The SC4 generation introduced four-electrode (toroidal) cell geometry on select models, significantly reducing polarization error in high-conductivity streams above 1 mS/cm. The SC4AJ sub-series refined connector standardization, adopting the AJ-type bayonet connector interface that provides IP67-rated sealing and tool-free field replacement — a direct response to maintenance feedback from refinery turnaround operations where sensor swap time is a critical KPI.

Compatibility across generations requires attention: SC4AJ sensors use the AJ connector standard and are not directly interchangeable with older SC4G (G-type connector) or SC4S (S-type connector) sensors without an adapter cable. When integrating into legacy ISC40G transmitters, a dedicated adapter harness (part: K9289HA) is required. Modern FLXA21 analyzers accept SC4AJ sensors natively via the SC4AJ input module. As the ISC40G and ISC40S transmitter lines have reached end-of-life, the installed base of SC4AJ sensors in the field now frequently requires lifecycle extension support rather than system-level upgrades.

SC4AJ Full Catalog & Functionalities (SKU List)

The following SKUs represent verified models within the Yokogawa SC4AJ conductivity sensor series, organized by application and cell constant classification:

Standard Contacting Conductivity Sensors (Low-to-Mid Range)

• SC4AJ-S-AD-09: Submersion/insertion sensor, cell constant K=1.0 cm⁻¹, PEEK body, AJ connector, range 0.01–200 mS/cm, standard process water applications.
• SC4AJ-S-AD-19: Insertion type, cell constant K=1.0 cm⁻¹, extended cable length (5 m), suited for tank-side mounting with remote transmitter.
• SC4AJ-S-AD-29: Insertion type, cell constant K=1.0 cm⁻¹, 10 m cable, for installations requiring long cable runs between sensor and analyzer panel.
• SC4AJ-S-BD-09: Submersion type, cell constant K=10.0 cm⁻¹, PPS body, optimized for high-conductivity streams (cooling tower blowdown, brine circuits).
• SC4AJ-S-BD-19: Submersion type, K=10.0 cm⁻¹, 5 m cable, high-conductivity with extended reach.
• SC4AJ-F-AD-09: Flow-through cell configuration, K=1.0 cm⁻¹, PEEK, for closed-loop piping systems requiring in-line measurement without open-tank access.
• SC4AJ-F-AD-19: Flow-through cell, K=1.0 cm⁻¹, 5 m cable, in-line piping with remote transmitter placement.
• SC4AJ-F-BD-09: Flow-through cell, K=10.0 cm⁻¹, PPS body, high-conductivity in-line measurement for chemical injection monitoring.
• SC4AJ-F-BD-19: Flow-through cell, K=10.0 cm⁻¹, 5 m cable, extended installation for high-conductivity in-line loops.
• SC4AJ-S-CD-09: Submersion type, cell constant K=0.1 cm⁻¹, ultra-pure water and low-conductivity pharmaceutical water systems (WFI, purified water loops).
• SC4AJ-S-CD-19: Submersion type, K=0.1 cm⁻¹, 5 m cable, low-conductivity with extended cable for remote analyzer placement.
• SC4AJ-F-CD-09: Flow-through, K=0.1 cm⁻¹, PEEK, in-line ultra-pure water measurement, semiconductor and power generation applications.
• SC4AJ-S-AD-09-T: Submersion type, K=1.0 cm⁻¹, with integrated Pt1000 temperature element for automatic temperature compensation (ATC) without external temperature sensor.
• SC4AJ-S-BD-09-T: Submersion type, K=10.0 cm⁻¹, integrated Pt1000 ATC, high-conductivity streams with on-sensor temperature measurement.
• SC4AJ-F-AD-09-T: Flow-through, K=1.0 cm⁻¹, integrated Pt1000 ATC, in-line process water with combined conductivity and temperature output.
• SC4AJ-S-AD-09-H: Submersion type, K=1.0 cm⁻¹, Hastelloy C-276 electrodes, for corrosive acid/alkali streams where standard PEEK electrode material is insufficient.

Sourcing Hard-to-Find & Obsolete SC4AJ Parts

The SC4AJ series, while still listed in Yokogawa's current catalog, is increasingly difficult to source through standard distribution channels due to long lead times from the factory (typically 8–16 weeks for non-stocked configurations) and the discontinuation of associated transmitters (ISC40G, ISC40S). DriveKNMS maintains a dedicated inventory of SC4AJ sensors and compatible accessories sourced through authorized secondary market channels, including decommissioned plant asset liquidations and certified refurbishment programs.

For end-users operating CENTUM CS 3000 or legacy CENTUM V DCS platforms where a full analyzer upgrade is not feasible within the current maintenance budget cycle, DriveKNMS provides like-for-like SC4AJ replacements that restore measurement loop functionality without requiring transmitter reconfiguration or DCS I/O card changes. All sourced units are accompanied by full traceability documentation including original manufacturer labeling, date codes, and where applicable, calibration certificates traceable to national standards.

Quality Control for the SC4AJ Range

Each SC4AJ sensor processed through DriveKNMS undergoes a structured verification protocol prior to dispatch. Cell constant verification is performed using NIST-traceable conductivity standard solutions at three concentration points corresponding to the sensor's rated range. Connector integrity is inspected under 10× magnification for pin corrosion, seal degradation, and mechanical damage to the AJ bayonet locking mechanism. Cable insulation resistance is tested at 500 VDC to confirm no moisture ingress or insulation breakdown along the full cable length. Temperature element continuity and resistance accuracy (Pt1000 at 0°C reference) are verified on units equipped with integrated ATC. Sensors that do not meet Yokogawa's published specification tolerances are quarantined and not offered for sale.

For SC4AJ availability, cross-reference requests, or bulk procurement inquiries:

• Email: [email protected]
• WhatsApp: +86 18359293191
• Web: driveknms.com