Yokogawa SC4AJ-S-AD-09 Conductivity Sensor

Product Details

SC4AJ-S-AD-09 Product Description

The Yokogawa SC4AJ-S-AD-09 is a precision four-electrode conductivity sensor engineered for seamless integration within the FLXA21 and FLXA202 liquid analyzer platforms. Designed to operate as a system-matched component rather than a standalone instrument, the SC4AJ-S-AD-09 delivers stable, high-accuracy conductivity measurement across demanding process environments — from chemical dosing loops and cooling water circuits to demineralised water quality monitoring and effluent treatment systems. Its role within the broader control architecture extends well beyond signal generation: it serves as the primary data source for conductivity-based process decisions that propagate through the control layer, the historian, and ultimately the SCADA or DCS supervisory system.

The SC4AJ-S-AD-09 achieves its full operational value when deployed as part of a coherent, layered automation architecture. At the field level, the sensor connects directly to the Yokogawa FLXA21 or FLXA202 two-wire liquid analyzer transmitter, which conditions the raw conductivity signal and provides local display, alarm management, and digital communication. The FLXA transmitter outputs a calibrated 4–20 mA signal or communicates via HART 7, FOUNDATION Fieldbus H1, or PROFIBUS PA, depending on the fieldbus topology selected for the plant.

In a FOUNDATION Fieldbus segment, the FLXA21 integrates directly into a Yokogawa CENTUM VP or ProSafe-RS safety instrumented system without requiring additional signal converters, preserving signal integrity from sensor to controller. For PROFIBUS PA installations, a DP/PA segment coupler — such as the Pepperl+Fuchs KFD2-BR-1.PA or equivalent — bridges the field segment to the PROFIBUS DP backbone connected to the process controller. In HART-enabled architectures, the signal is routed through a Yokogawa STARDOM FCN/FCJ remote I/O node or a conventional AI (Analog Input) module within the DCS marshalling cabinet, where it is scaled, alarmed, and historised.

Power supply integrity is critical for stable conductivity measurement. The SC4AJ-S-AD-09 / FLXA21 combination operates on a 24 V DC loop supply, typically sourced from a Yokogawa PW302 or equivalent DIN-rail power supply unit with redundant feed capability. In hazardous area installations, an intrinsic safety barrier or Zener barrier is inserted between the field device and the control room, ensuring compliance with ATEX or IECEx zone classifications.

At the control layer, the conductivity measurement feeds into PID control blocks within the DCS or SCADA platform — for example, a Yokogawa CENTUM VP FCS (Field Control Station) — where it drives chemical dosing pumps, blowdown valves, or conductivity-based interlock sequences. In water treatment applications, the conductivity loop is often interlocked with a flow transmitter and a turbidity sensor to form a composite water quality control strategy. The historian module — such as Yokogawa Exaquantum — archives conductivity trends for regulatory compliance and process optimisation.

For redundancy-critical installations, a dual-sensor arrangement using two SC4AJ-S-AD-09 units connected to separate FLXA21 transmitters provides measurement redundancy, with the DCS performing median or switchover selection logic. This architecture is common in pharmaceutical purified water (PW) and water for injection (WFI) loops where continuous conductivity monitoring is mandated by GMP regulations.

Chemical and Petrochemical Processing: The SC4AJ-S-AD-09 is widely deployed in cooling water conductivity control, where it monitors dissolved solids concentration to trigger blowdown sequences and chemical inhibitor dosing. Its four-electrode design minimises polarisation errors at higher conductivity ranges, making it suitable for concentrated brine or acid/alkali neutralisation loops in chemical plants.

Power Generation and Utilities: In steam cycle chemistry monitoring, the sensor measures condensate and feedwater conductivity to detect condenser tube leaks or contamination events. Integrated with the plant DCS, the conductivity signal triggers alarms and automatic isolation valves, protecting boiler integrity and turbine efficiency.

Pharmaceutical and Biotechnology: Purified water and WFI systems require continuous, validated conductivity measurement compliant with USP <645> and EP 2.2.38 standards. The SC4AJ-S-AD-09 paired with the FLXA21 supports multi-point calibration and audit trail logging, meeting GMP documentation requirements.

Water and Wastewater Treatment: Municipal and industrial water treatment plants use conductivity measurement to monitor ion exchange resin exhaustion, RO membrane performance, and effluent quality before discharge. The sensor's IP67 rating and wide temperature tolerance ensure reliable operation in outdoor or partially submerged installations.

Food and Beverage (CIP Monitoring): Clean-in-place (CIP) systems rely on conductivity to detect phase transitions between water, caustic, acid, and product phases. The SC4AJ-S-AD-09's fast response and hygienic-compatible wetted materials support accurate phase detection, reducing chemical waste and cleaning cycle time.

Q1: Is the SC4AJ-S-AD-09 compatible with both FLXA21 and FLXA202 analyzers, and can it be used in a HART multiplexer architecture? Yes. The SC4AJ-S-AD-09 is fully compatible with both the FLXA21 (two-wire, loop-powered) and the FLXA202 (four-wire, panel-mount) liquid analyzer platforms. In HART multiplexer architectures — using devices such as the Yokogawa YHC5150X HART communicator or a third-party HART multiplexer connected to the DCS — the FLXA21 transmitter exposes secondary variables (temperature, sensor diagnostics) alongside the primary conductivity value, enabling comprehensive asset monitoring without additional wiring.

Q2: What are the installation and commissioning requirements for integrating the SC4AJ-S-AD-09 into an existing PROFIBUS PA segment? Integration into a PROFIBUS PA segment requires the FLXA21 to be configured with the PROFIBUS PA communication option. The device GSD file must be imported into the DCS engineering tool (e.g., Yokogawa CENTUM VP Builder or Siemens SIMATIC PDM). Segment loading calculations should confirm that the additional device does not exceed the segment's current budget. Physical installation follows standard PA wiring practices: shielded twisted-pair cable, correct termination resistors at both ends of the segment, and verification of bus voltage at the device connector (minimum 9 V DC). Commissioning includes address assignment, cyclic data mapping, and a wet calibration using certified conductivity standards.

Q3: What does the 12-Month Warranty cover, and how does NANKMOS support long-term inventory availability for the SC4AJ-S-AD-09? NANKMOS provides a 12-Month Warranty on the SC4AJ-S-AD-09 covering manufacturing defects, sensor electrode integrity, and cable assembly quality under normal operating conditions. Each unit undergoes pre-shipment functional testing including conductivity cell constant verification and insulation resistance checks. For long-term project support, NANKMOS maintains buffer stock of the SC4AJ-S-AD-09 and compatible FLXA21 transmitters to support multi-year maintenance contracts, spare parts programmes, and emergency replacement requirements. Contact [email protected] or +86 18359268345 for volume pricing, lead time confirmation, and project-specific supply agreements.