Liquid Analyzer for Turbidity and Chlorine FLXA402T

Providing reliable turbidity and chlorine measurements in Water Treatment Plants since 1959
No.1 Process analyzer supplier to Japanese market*

“Reduce initial cost with reliable products”

“Want to monitor status from remote place”

Many of our customers face these challenges - Yokogawa Turbidity and Chlorine Analyzers resolve them.

The FLXA402T offers multiple connection possibilities, eliminating the need for multiple analyzers and providing greater flexibility. This four-wire analyzer includes a color HMI and an easy touchscreen operation with a simple menu structure in 8 languages for simple and efficient setup and configuration.

With its modular design, the FLXA402T analyzer offers a range of measurement choices with the respective sensor module, including turbidity, chlorine, pH, Conductivity, and 4-20mA input. Dual sensor measurements save your install space and offer additional functionalities, such as pH compensation for the Chlorine analyzer.

*Based on a Yokogawa survey in 2019

About OpreX

OpreX is the comprehensive brand for Yokogawa’s industrial automation (IA) and control business and stands for excellence in the related technology and solutions. It consists of categories and families under each category. This product belongs to the OpreX Analyzers family that is aligned under the OpreX Measurement category.


FLXA402T Features

Support up to 2 sensors

FLXA402T has a modular structure and can insert up to 2 sensor modules. You can choose the Turbidity module or Chlorine module as a 1st module, and Turbidity module, Chlorine module, pH module, or conductivity module is available as a 2nd module.

FLXA402T Module

Expert Guide: Clear Touch Panel Display for Improved Operability

The FLEXA series analyzer provides improved operability with intuitive touchscreen operation, featuring a clear display and user-friendly indication with eight languages*. Sensor status and estimated maintenance time notification improve efficiency. The interactive screen is housed in a robust aluminum die-cast housing. ​​​

easy to use touch screen

*8 languages: English, Chinese, Korean, German, French, Spanish, Portuguese, Japanese

Advanced Flexibility: Modular Design for Increased Scalability

The FLEXA™ series analyzer features a modular design with replaceable sensor modules, enabling the construction of various of systems. FLXA402T allows for the connection of up to two possible sensors resulting in a reduction in CAPEX and OPEX.


Preparing for the Future

Industrial automation is moving toward SMART products, with sensors changing from analog to digital SMART. This transition can affect plant operations and take time to implement fully.

In addition to being a high-performance standalone analyzer, the FLXA402T is also a component of the Yokogawa SENCOM4.0 Platform, SMART sensor systems give you more insight because they possess in-depth knowledge of their health status for predictive asset management and sensor condition to ease troubleshooting.

With the SENCOM4.0 Platform, upgrading to the next generation SMART product is easy and can be done at any time with little impact on operations.

Easy to get information and operate from remote place

Data Mobility

SD card or Ethernet for easy data transfer and remote service, allowing for more in-depth process analysis. 


  • Turbidity of tap water, sewage, river water and water used in general processes
  • The Chlorine Analyzers intended for measurements in the water distribution network, at pumping stations, water delivery points, schools, and public facilities.

Analyzer specialized for water applications

System Configuration

Turbidity and Chlorine 2 in 1 system configuration

The first module can be connected the Chlorine sensor unit or the Turbidity detector unit, and the second module can be connected the Chlorine sensor unit, Turbidity detector unit , pH sensor or conductivity sensor. For example, Chlorine sensor unit and Turbidity detector unit can be controled by one Liquid Analyzer.

System Configuration FLXA402T-FC800D-TB820D

Turbidity Measurement 

Easy to clean cell structure, Automatic wash system, Long life time light source

Right Angle Scattered Light Turbidity Detector TB820D
Surface Scattering Light Turbidity Detector TB830D

The TB820D and TB830D are SENCOM4.0 family and can connect to FLXA402T. Thanks to smart unit equipped detector, TB820D and TB830D give you more insight in ordinary operation.

Learn more


Chlorine Measurement 

Minimize chlorine injection, remote maintenance and reduce maintenance time

Non-reagent Type Free Available Chlorine Sensor Unit FC800D

The FC800D is SENCOM4.0 family and can connect to FLXA402T. Thanks to smart unit equipped behind of electrode unit, FC800D gives you more insight in ordinary operation.

Learn more


Residual Chlorine Sensor Unit RC800D

The RC800D is suitable for various water condition measurements and gives you stable and high quality measurement thanks to rotation electrodes and high quality reagent pump.

Learn more

FLXA402T and RC800D System

pH and Conductivity Measurement

You can find the best pH and Conductivity solution for your process

YOKOGAWA’s pH and Conductivity sensors are highly reliable and very unique. You can select the most valuable sensor.

pH and conductivity sensors




Yes, FLXA402T+PG400 supports ultrasonic cleaning for both Turbidity detectors.
Yes, 0.2μm mesh filter and 1.0μm mesh filter for TB820D are same as TB750G. You can select zero turbidity filter in case; Measuring range is 2.0 NTU or greater: 1μm Measuring range is less than 2.0 NTU: 1μm + 0.2μm ...
Yes, you can use pH compensation for -F1 model. Please use this function in case of fluctuate pH value. If it is difficult to decide which is better, please fill pH fluctuation in the Inquiry Sheet and contact us. ...
No, you don’t need to do any adjustment. Just replace light source.
Yes, you can buy flow-cell and glass windows as a spare part.
We strongly recommend using head tank in any case for stable measurement. If your facility has enough pretreatment and there are no bubbles, you can install the TB820D without head tank. D1 pressurized head tank is suitable for under 2 NTU measuremen...
K9411UA and K9726EF consist of filter case and filter element. K9008ZD and K9726EG are only filter element and you can use them in case of filter replacement.
Parts No. Name Remarks QTY Recommended Replacement Period K8003DN LED ASSY (Red Light) For code – NT. RED light source. For red light sources. 1 3 years K8003DP LED ASSY (Infrared Red Li...
The rotating electrode material changes. -F1 = Gold electrode+celamic beads. -C1 = Gold/Platinum alloy+glass beads. They change the plateau characteristic and reduce combined chlorine sensitivity. On the other hand, available pH range becomes smaller...
Parts No. Name Remarks QTY Recommended Replacement Interval K8005JB Measurement electrode (rotating electrode) Gold electrode for –F1,-F2, and –F3 1 Yearly K8005JC Measurement electro...
Air purging is required for electrode unit and liquid pump by air pump or compressor air (industrial air). It is required to protect electrode from chlorine gasses which will affect the metal parts.
The FC800D and the RC800D are not suitable for outdoor installation. Strongly recommend installing inside because of pump structure. If you want to install outside, a separate rainproof cover is required and take care install place environment (no co...
Rotation electrode will get damaged in case there is no water in the measurement cell. To avoid this situation, the FC800D and the RC800D measurement electrode rotation is automatically stopped. This function makes rotation electrode lifetime longer ...
Beads become gradually smaller because of friction, and decreases cleaning efficiency. So, we recommend replacing beads once a year.
FLXA 402T Multi Sensor variation 1st module TB820D FC800D FC800D FC800D FC800D TB820D TB820D 2nd module TB820D FC800D TB820D Analog pH Analog Conductivity Analog pH sensor Analo...
You don't need to do any difficult setting. The FLXA402T configurations have already optimized for selected measurement when it is shipped.
Maximum digit is three decimal points, default is 2 decimal points.
PH4, pH7 and pH9 tables complied by NIST, DIN and US standards are available.
The FLXA402T can connect a pH sensor, but an ORP sensor is not available. For ORP measuring, please select the FLXA402. (Not FLXA402T)
Static conductivity sensor is available. Inductive conductivity sensors are not available. For inductive conductivity sensor measuring, please select the FLXA402. (Not FLXA402T)
Conductivity measuring is available in the FLXA402T. For resistivity measuring, please select the FLXA402. (Not FLXA402T)
Maximum 20m is available. If you want to use more than 20m cable, please contact us.
Yes, you can save and copy the FLXA402T configurations by SD card. It realizes easy installation and replacement.
Within ordered range, you can set the FLXA402T analog output range seamlessly. Cannot change ordered analyzer measurement range.
Parts No. Name Remarks QTY Recommended Replacement Interval - Primary acetic acid (CH3COOH) grade: over 99.0+% For reagent preparation -   - Sodium acetate (CH3COONa) grade: over 98.0%...
  -F1 -C1 -F2, -F3 Chlorin conc < 1 mg/L >1 mg/L < = 3 mg/L < = 3 mg/L < = 5 mg/L < = 10 mg/L pH pH: 6 to 8 pH: 6.5 to 7.5 pH: 6.5 to 7.5 pH: 6.5 to 7.5 ...




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Smart Water Management System providing clean and safe water.
Yokogawa provides total water management system including Turbidity and Free Chlorine measurement.

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