Yokogawa FLXA21-D P-D-CH-D1-NN-A-N-LA-N-NN/U Dissolved Oxygen Analyzer

Overview

The Yokogawa FLXA21-D P-D-CH-D1-NN-A-N-LA-N-NN/U is a 2-wire module-type liquid analyzer transmitter from Yokogawa’s FLEXA series, factory-configured for dissolved oxygen (DO) sensor input. Built on the same proven FLXA21 platform used for pH/ORP, conductivity, and inductive conductivity measurement, this DO-configured variant accepts both galvanic and polarographic dissolved oxygen sensors, giving process engineers a single reliable transmitter platform for continuous on-line oxygen monitoring in water treatment, power generation, and pharmaceutical process water systems.

As the official authorized partner and exclusive regional representative for Yokogawa in Oman and the GCC, Seven Star LLC proudly supplies the Yokogawa FLXA21-D dissolved oxygen analyzer to power plants, water treatment facilities, and process industries across the Sultanate of Oman, Muscat, and the wider GCC region. Our instrumentation division validates the exact model code against each customer’s sensor configuration before dispatch, ensuring the ordered analyzer arrives correctly configured and ready for commissioning on regional projects.

Operating Principle

The Yokogawa FLXA21-D operates by accepting a low-level current signal from an external dissolved oxygen sensor and converting it into a calibrated, temperature-compensated DO reading. For galvanic-type DO sensors, the sensor generates its own driving voltage internally; for polarographic-type sensors, the FLXA21-D itself supplies the external driving voltage required for the electrochemical reaction at the sensor tip. The transmitter accepts an input range of 0 to 50 µA for galvanic sensors and 0 to 1 µA for polarographic sensors, translating the raw current signal into a dissolved oxygen concentration across a 0 to 50 mg/l (ppm) measurement span.

Because dissolved oxygen readings are highly temperature-dependent, the FLXA21-D incorporates automatic temperature compensation using Pt1000 or NTC22k temperature elements built into the DO sensor assembly. The transmitter continuously monitors sensor health — tracking impedance, membrane condition, and signal stability — and raises diagnostic alerts when the sensor requires cleaning, recalibration, or replacement. This self-diagnosis capability reduces unplanned maintenance visits and keeps continuous water-quality monitoring loops running with minimal operator intervention.

Engineering Design of the Yokogawa FLXA21-D

The Yokogawa FLXA21-D is housed in a rugged, wall or pipe-mountable enclosure suited to both indoor plant rooms and outdoor field installations. A high-visibility backlit LCD display presents live DO concentration and process temperature simultaneously across dual measurement channels, while a sealed four-button keypad behind the front cover allows on-site calibration, range configuration, and diagnostic review without opening the enclosure to the elements. Cable entry is provided through multiple gland fittings on the underside of the housing, keeping wiring connections protected from moisture ingress in humid GCC coastal and desalination plant environments.

As a genuine 2-wire loop-powered device, the FLXA21-D transmits its 4-20 mA output signal over the same two conductors used to supply power, dramatically simplifying field wiring compared to separately powered 4-wire analyzer systems. The modular internal architecture allows the same physical transmitter housing to be factory-configured for pH/ORP, conductivity, inductive conductivity, or dissolved oxygen measurement simply by changing the internal sensor input module and firmware configuration — the P-D-CH-D1-NN-A-N-LA-N-NN/U code specifies the exact DO input configuration, output, and approval options for this unit.

Key Features

The Yokogawa FLXA21-D dissolved oxygen analyzer combines flexible sensor compatibility with rugged 2-wire field construction. Core capabilities include:

• Compatible with both galvanic and polarographic dissolved oxygen sensors on a single transmitter platform.
• Dissolved oxygen measurement range of 0 to 50 mg/l (ppm) with automatic Pt1000/NTC22k temperature compensation.
• Continuous self-diagnostics that monitor sensor condition and flag cleaning, calibration, or replacement needs.
• Genuine 2-wire, loop-powered 4-20 mA operation that simplifies field wiring and reduces installation cost.
• Backlit dual-channel LCD display for simultaneous viewing of DO concentration and process temperature.
• Rugged wall or pipe-mount enclosure suitable for indoor and outdoor installation in humid process environments.
• Shared FLEXA hardware platform with pH/ORP and conductivity variants, simplifying spares strategy across a plant.
• Factory-configured exact model code ensures the ordered unit matches the customer’s specified sensor and output requirements.

Industrial Applications

Dissolved oxygen monitoring with the Yokogawa FLXA21-D is essential across power generation, water treatment, and process industries throughout Oman and the GCC. In power plant boiler feedwater and condensate systems, the analyzer verifies that dissolved oxygen levels remain low enough to prevent corrosion of high-pressure steam piping and heat exchangers, protecting critical rotating and static equipment from oxygen-driven pitting.

As the officially authorized partner for Yokogawa, Seven Star LLC distributes the FLXA21-D to municipal and industrial water treatment plants, RO desalination facilities, and pharmaceutical process water systems within the Sohar and Salalah economic zones, where continuous DO monitoring supports both regulatory compliance and process optimization. Aquaculture and wastewater aeration basin operators across the region also depend on this analyzer to maintain optimal oxygen levels for biological treatment processes, with Seven Star LLC’s local stock and technical support minimizing downtime during sensor or transmitter replacement.

Technical Specifications

Full technical parameters for the Yokogawa FLXA21-D dissolved oxygen analyzer:

Call To Action

To submit a formal Request for Quote (RFQ), verify the exact model code configuration, or download the complete technical datasheet for the Yokogawa FLXA21-D dissolved oxygen analyzer, please contact the instrumentation division at Seven Star LLC today. As the authorized partner for Yokogawa in Oman and the GCC, our engineers cross-check every RFQ model code against Yokogawa’s official configuration tables before confirming an order, ensuring the unit you receive is built exactly to your process requirements.