Non-reagent Type Free Available Chlorine Sensor Unit FC800D

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

"Reliable Chlorine monitoring and minimize Chlorine injection"

"Continuous automatic cleaning and achieved less maintenance time "

"Maintenance remotely for efficient process management"

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

The FC800D non-reagent free available chlorine analyzer adopts the polarographic method, and a unique rotating electrode provides a continuous online measurement of free available chlorine concentration.

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

The FC800D is suitable for water distribution measurements at pumping stations, water delivery points, schools, and public facilities.
*Based on a Yokogawa survey in 2019


Reagent free measurement, Reduced maintenance due to rotating electrode

  • Amperometric measurement of free chlorine (polarographic method)
  • Measure Free chlorine continuously without reagent
  • Unique rotation electrode method keeps sensor clean and reduces maintenance cycle
  • Easy maintenance structure, modularized motor unit and diagnostics functions strongly support regular maintenance
  • FC800D is equipped with Manual calibration and Auto Calibration, 2 points correction, Basic (reference) sensitivity calibration, and circuit open Zero calibration
  • Remote range switching is available
FC800D Open

FC800D Display : easy to use touch screen


Unique rotating electrode method keeps sensor clean

Continuous automatic cleaning with beads realizes contamination-resistant and stable measurement
You can reduce maintenance time dramatically thanks to easy maintenance structures.

FC800D Configuration

  • Smart unit: Built-in Main board
  • Electrode Unit: Built-in Motor, Rotating contact
  • Beads Case: Houses cleaning beads
  • Needle valve for flow rate adjustment
  • Rotating electrode: Rotating electrode with beads keep the surface polished. This keeps the measurement electrode contaminant free providing long term stability.
  • Reference electrode: Built-in temperature sensor for temperature compensation


Each process at treatment plant: from reservoir to treated water, distribution system

Water Purification Treatment

  • Stabilization 
  • Flocculation 
  • Settling Basins 
  • Chlorination 
  • Clean water reservoir 
  • Distributing pump 
  • Distribution tank & Piping


Use case 


Measured Object Free chlorine in tap water
Measuring System Amperometric method (Polarographic method) using rotating electrode
Measuring Range Free chlorie 0-1 to 0-3 mg/L(-F1), Combined chlorine insentive version 0-1 to 0-3 mg/L(-C1),
Free chlorie 0-5 mg/L (-F2) (*), Free chlorie 0-10 mg/L( -F3) (*)
(*) As for "-F2" and "-F3", please refer to the General Specifications.
Sample Condition (-F1, -C1) Temperature 0 to 50°C (Temperature compensation is effective within 0 to 40°C)
pH No pH fluctuation
pH6.5 to 7.5
(pH6.0 to 8.0 :Chlorine value 1mg/L(-F1))
Conductivity No conductivity fluctuation
100 to 300 μS/cm
(100 to 500 μS/cm :Chlorine value 1mg/L(-F1))
Flow Rate 0.1- 2.5 L/min
Pressure 1-150 kPa
SS (Suspended Solid) under 10 mg/L
Power Supply 100 to 240 V DC, 50/60 Hz
Digital Communication Modbus TCP/IP, Modbus RTU
Installation Indoor (Outdoor use requires protection against rain.Direct sunlight must be avoided.)


Performance (-F1 and -C1)

Linearity ±5% of reading or ±0.05mg/L whichever is greater
Repeatability ±1% of reading or ±0.01mg/L whichever is greater

* As for "-F2" and "-F3", please refer to the General Specifications.


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.




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. ...
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...
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.
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 ...
Within ordered range, you can set the FLXA402T analog output range seamlessly. Cannot change ordered analyzer measurement range.
Beads become gradually smaller because of friction, and decreases cleaning efficiency. So, we recommend replacing beads once a year.
  -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 ...




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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