Field-installation Type MLSS Meter (Four-Wire Transmission)

HU-200SS connects immersion type MLSS sensor (SS-90) and measures MLSS in activated sludge. A wide range (0-2000mg/L)of SS contents can be measured with excellent reproducibility using the near-infrared radiation transmission method. Any of the calibration curves of MLSS, Clay (inorganic mud) and Kaolin may be used as standard substances of SS. If "MLSS" is selected for an activated sludge treatment tank, "Clay" for the precipitation treatment of construction sludge, or "Kaolin" for white mud, a concentration can be obtained closer to an analyzed value.

Measurement range

Activated sludge(MLSS) 0 - 20000 mg/L
White inorganic powder 0 - 10000 mg/L
Gray inorganic mud 0 - 20000 mg/L

Division: Process Water
Manufacturing Company: HORIBA Advanced Techno Co., Ltd.


  • Responds to harsh conditions at the site process
      Operating temperature range(Transmitter):-20 - 55℃
      Rated power supply voltage: AC 100 - 240 V ± 10 % 50/60 Hz
      Robust aluminum die cast (Protection code:IP65)
  • CE Marking and FCC Compliance suitable for use at overseas sites



  • Sensor error can be detected immediately by self-diagnosis function
  • Designed to be environmentally friendly (Pb-free) in response to WEEE and RoHS
  • Three calibration curves are built-in and selectable according to the sample
  • Long-life LED light sources, and the elimination of ambient light by blinking
  • Near-infrared radiation transmission method with stable sensitivity


Easy maintenance

  • Easy to view big display
  • Easy operation
  • Calibration log memory
  • Screw terminals that do not fall off are used in the terminal block for wiring
  • PFA sensor head resistant to stain


Product nameIndustrial-use MLSS meter
Converter typeHU-200SS industrial-use MLSS converter
Detector typeSS-90 MLSS detector for industrial use
Measurable rangeActivated sludge (MLSS)0 to 20000 mg/L (MLSS)
Kaolin0 to 10000 mg/L (white inorganic powder)
Clay (inorganic mud)0 to 20000 mg/L (gray inorganic mud)
output setting
Activated sludge (MLSS)Arbitrary setting within the range from 0 to 1000 mg/L to 0 to 20000 mg/L
KaolinArbitrary setting within the range from 0 to 1000 mg/L to 0 to 10000 mg/L
Clay (inorganic mud)Arbitrary setting within the range from 0 to 1000 mg/L to 0 to 20000 mg/L
Display resolution1 mg/L (0 to 10000mg/L)
10 mg/L (10000 to 22000mg/L)
PerformanceRepeatabilityWithin a reading value ±3% or ±10 mg/L, whichever is larger. (sensor connecting sludge measured value)
Number of output points1
Output typeDC 4 mA to 20 mA, input/output insulation type
Load resistance900 Ω maximum
LinearityWithin ±0.08mA (for output only)
RepeatabilityWithin ±0.02mA (for output only)
Error outputWith the burnout capability (3.8 mA or 21 mA)
Hold capabilityEither the last value hold or the arbitrary value hold is to be selected.
Contact outputNumber of output points3
Output typeNo-voltage contact output
Contact typeRelay contact, SPDT (1c)
Contact capacity250 V AC, 3 A, 30 V DC, 3 A (resistance load)
R1, R2Selectable from upper limit alarm, lower limit alarm, transmission output Hold, and cleaning output.
(opened at alarm operation, closed usually, closed at power-off)
FAILError warning (normally closed; open when an error occurs; open when the power is turned OFF)
Description of alarm 
  • Setmting range: MLSS concentration within the measurable range
  • Delay time: 0 to 600 s
Cleaning outputNumber of output points1
Output typeActive voltage contact output (connected supply voltage output)
Contact typeRelay contact, SPST (1a)
Contact capacity250 V AC 0.5 A
Contact capabilitySolenoid valve drive for cleaning
0.1 h to 168.0 h
Cleaning time2 s to 600 s
Hold time2 s to 600 s
Timer accuracyWithin 2 min per month
Description of cleaning
  • Operation of the internal timer
  • Operation of the internal timer and external contact input
  • The internal timer is enabled only at the time of external contact input.
  • One of the cleaning trigger operations is selected (the internal cleaning sequence starts when external contact input is ON for at least 2 s).
Contact inputNumber of input points1
Contact typeNo-voltage a contact for open collector
ConditionON resistance: 100 Ω maximum
Open-circuit voltage: 24 V DC
Short-circuit current: 12 mA DC maximum
Contact capabilityCan be selected from cleaning directives and transmission hold.
Signal typeTwo-wire input/output insulation type (not insulated from transmission output)
CalibrationCalibration method 
  • Zero calibration: With clean water
  • Span calibration: Concentration conversion method using coefficient input
  • Working curve selection: (selection of activated sludge and inorganic mud)
There is a feature that allows you to match an instrument indicated value to a hand analyzed value of sludge (by the Mass method).
Self-checkSensor check errorSensor error
Converter errorCPU abnormality, ADC abnormality, memory abnormality
temperature range
−20℃ to 55℃ (without freezing)
Operating humidity
Relative humidity: 5% to 90% (without due condensation)
−25℃ to 65℃
Power sourceRated power supply
100 V to 240 V AC ±10% 50/60Hz
Power consumption20 V A (max)
OthersA power switch for maintenance is incorporated.
CE markingEMC   : EN61326-1
     Class A, Industrial electromagnetic environment
Safety : EN61010-1
RoHS  : EN50581
     9. Industrial monitoring and control instruments
FCC rulesPart15 Class A
StructureInstallationOutdoor installation type
Installation method50 A pole-mounted or wall-mounted
Protection classIP65
Material of caseAluminum alloy (coated with epoxy modified melamine resin)
Material of mounting
Material of hoodSUS304 (epoxy glue degeneration melamine resin painting)
Material of display windowPolycarbonate
Display elementReflective monochrome LCD
180 (W) mm × 155 (H) mm × 115 (D) mm (excluding brackets)
MassMainframe: approx. 3.5 kg, hood, bracket: approx. 1 kg

*1:  The surge test specified in the EMC Directive for CE Marking shall not apply to the case when a sensor cable, transmission cable, or contact input cable is extended for 30 m or longer.

*2:  An arrester (electric discharge voltage: 400 V) is provided for transmission output, contact input, and communications. However, incorporate and use an optimal surge absorption element on the connected line according to the ambient environment, equipment installation situations, and externally connected equipment, etc.


Product nameMLSS detector for industrial use
Measuring principleLight transmission method
Light sourceInfrared LED, 880 nm, approx. 10 Hz, AC blinking
Detector(transmitted light/reference light)
Cell lengthApprox. 7 mm
Data transferRS-485 (communication with the converter)
Self-checkWater immersion detection
Operating temperature range5℃ to 50℃ (without freezing)
Storage temperature−25℃ to 65℃
Measured liquid pressure0 MPa to 0.2 MPa
Material of wetted partPPO SUS316 PFA FKM EPDM PVC
Cable length10 m (standard), maximum extension: 50 m (overall length: 60 m)
Power source12 V DC supplied from the HU-200SS converter
External dimensions48 mm in diameter x 250 mm in length (excluding the cable)
MassApprox. 0.8 Kg (excluding the cable)

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