• Drinking water
  • Process optimisation of wastewater treatment plants
  • Industrial and municipal wastewater
  • Mineral water monitoring
  • Surface water


The 3S colorimeter is a compact analytical instrumentation for online analysis and process monitoring. The colorimeter is based on a color-developing chemical reaction carried out inside the analyzer's glass cell. The sample, coming from an external reservoir or process stream is autonomously grabbed by the instrument and mixed with the appropriate reagents to make the reaction happen. The analyzer uses an LED light source and a photodiode to photometrically measure the developed color intensity (absorbance). The absorbance is proportional to the concentration of the target chemical species (analite).


  • Low reagents consumption and analytical reliability thanks to our custom designed miniature peristaltic pumps
  • Dual compartment design to guarantee a complete separation between the electronics and the hydraulic section
  • Color touchscreen to show the last measured value clearly, and to set all the options and settings via an user friendly interface
  • Datalogger function with data history in graphical form and USB download
  • Automatic calibration, validation and cleaning to reduce down time and operator intervention, their frequency can be freely set by the user
  • Fully integrable in industrial automation via the analog outputs (2 x 4-20 mA channels), digital output (2 relays + ModbusRTU) and digital input (voltage free contact)

The instrument is ideal for potable water or suface water analysis and with the addition of a dilution module is also capable of the determination of nitrates in complex matrices such as urban and industrial wastewaters.
The determination ranges of the nitrate analyzer vary from trace μg/L to 25.0 mg/L N-NO3 (80 mg/L NO3) using the (optional) internal dilution module. The result can be expressed as NO3 or N-NO3.


Both hydrazine and copper catalyst reagents are used to reduce Nitrate to Nitrite in a basic medium inside a heated reaction cell. A sulfanilamide and N-(1-naphthyl)-ethylene diammonium dichloride reagent is added to react with the Nitrite to form a purple colored compound. The absorbance intensity is proportional to the Nitrite concentration in the sample and is measured at 525 nm


Measured parameter NO3-


(Ø 26 mm) 2 - 400 ppb N-NO3 (1.28 ppm NO3)
(Ø 16 mm) 4 - 650 ppb N-NO3 (2.08 ppm NO3)
(with dilution) 25 ppm N-NO3 (80 ppm NO3)


* if two values take whichever is greater.
(Ø 26 mm) ± 2 ppb / ± 5%
(Ø 16 mm) ± 5 ppb / ± 5%
Limit of detection 2 ppb
Wavelength 525 nm
Demineralized water Not required
Termoregulation 37 °C
Interferences Amines, urea, iodides.
Reference DIN EN 26 777
Number of reagents 3
Min. analysis time 11 minutes
Default analysis time 20 minutes

Reagent consumption**

** per month, at the default analysis frequency.
(Ø 16 mm) 4 L

Technical Specifications

Model 3S-CL
Sampling Mode Batch, with freely settable frequency.
Sample Pressure: Atmospheric
Temperature: 5 ‐ 45°C (41 ‐ 113°F)
Flow Rate: 80 to 500 mL/min
Connection: 6 mm (¼-in.)
Drain Pressure-free drain
Connection: 12 mm (½-in.)
Input Streams 2
Material Epoxy-coated stainless steel AISI 304
Dimensions (H x W x D) 604 x 380 x 210 mm (23.6 x 14.8 x 8.2 in)
Weight 20 kg (44 lbs)
Power Supply Input Voltage: 115 VAC,230 VAC
Power consumption: max. 80 W
Output signals 2 x 4-20 mA analog outputs
Modbus via RS485,Ethernet
Alarms 2 SPDT programmable voltage-free relays
Digital Input None, Online, Start Extra, Skip Idle, Emergency Stop
Ambient Temperature 5 - 45 °C (41 - 113 °F)
Ambient Humidity 10 - 90 % RH (non-condensing)
Protection Grade IP54 (indoor only, outdoor use possible with external cabinet, not included)