Nitrate “NICO®" for fresh water

                    For saltwater use OPUS

NICO accurate

Nitrate Probe Configurator

 (Download NICO® Manual pdf)

Fully Compatible with Kisters® Software 

 For detailed ranges and accuracies for NICO® click here 


Why are continuous nitrate sensors needed?

Nitrate in water can vary in three dimensions and in time due to many stressors

Sampling once per year, seasonally, or monthly does not provide adequate information about the variability of nitrate in the environment

HydroTech new low-cost nitrate meter by Trios  

Based on the device platform concept of TriOS sensors like OPUS, LISA and VIPER, TriOS introduces NICO: a low-cost UV photometer for the determination of nitrate. The four detection channels enable a precise optical determination of nitrate by absorption, taking into account turbidity and organic substances that pose a problem for many products currently on the market.

An internal temperature correction additionally increases stability of the measured values.

Equipped with our G2 interface with web browser configuration and internal data logger NICO includes features that are much more advanced than those of comparable devices available on the market.

The unified platform of all TriOS photometers also facilitates a standardized spare parts and consumables system, which allows the use of a wide range of accessories for our devices. Furthermore the cutting-edge G2 interface enables quick   integration into third-party systems

The science behind the NICO and OPUS

The NICO and OPUS operate on the principle that nitrate absorbs radiation in the ultra-violet (UV) region of the electromagnetic spectrum at a characteristic wavelength of about 220 nm.

Pulses of UV light are transmitted through a sample path of water (typically 20 mm), received and spectrally analysed. The amount of UV absorbed by the water sample is proportional to the concentration of nitrate in the water. The processor compares the intensities of the two received beams, derives the nitrate concentration and sends this to a recorder such as a web-enabled datalogger.

NICO Science graph

The sensor may be located in a stream, or alternatively, above water-level and have water pumped to it via a flow cell.  The optical windows the UV passes through, are usually made from transparent quartz. This can resist abrasion by the hardest materials likely to be present in the water stream.

These windows can be automatically cleaned by compressed air, a built-in wiper or ultrasonic vibrator. Monthly site visits enable a physical verification sample and also provide an opportunity to inspect and clean the instrument manually.

Strengths and weaknesses of UV multispectral sensors

  • Pros:
    •  Precise, accurate and stable
    • Inexpensive to operate
    • Minimal maintenance
    • Measure over a wide range
    • No chemicals needed
    • Robust and durable
    • Fast response
    • Spectra may also detect e.g. turbidity
    • Easy to deploy… ‘plug and measure’
    • Factory pre-calibration (may need ‘local water’ calibration)
    • Independent of water temperature
  • Cons:
    • Power use: Requires power onsite 
    • Other constituents (notably CDOM and turbidity) can interfere with optics


  • Proven UV-absorption method
  • Without sampling and preparation of test samples 
  • Real-time sensor
  • Without reagents
  • Optical window with nano coating 


  • Sewage treatment plants
  • Environmental monitoring
  • Drinking water monitoring

Technical Specifications

Measurement­ technolog:

  • light source : Xenon flash lamp
  • detector: 4 photo diodes + filter

Measurement principle: Attenuation

Optical path0.3 mm, 1 mm, 2 mm, 5 mm, 10 mm, 50 mm

Parameters: NO -N, NO NO -N, NO (calibrated with NO standard solution)


Range and accuracy:

The optical path on the NICO can be modified by the end user from 0.3 mm, to 1 mm, 2 mm, 5 mm or 10 mm. The optical path size determines the range and the accuracy of the sensor.

Optical Path Size (mm): Range (NO3-N) ; (NO3)  /  Accuracy (NO3-N) ; (NO3)

  • 0.3mm:     (0-200) ; (0-886)    / ± (5% of the reading + 3.3) ; (5% of the reading + 14.5)
  • 1mm:        (0-60) ; (0-266)      / ± (5% of the reading + 1) ; (5% of the reading + 4.4)
  • 2mm:        (0-30) ; (0-133       / ± (5% of the reading + 0.5) ; (5% of the reading + 2.2)
  • 5mm:        (0-12) ; (0-53)        /  ± (5% of the reading + 0.2) ; (5% of the reading + 0.88)
  • 10mm:      (0-6) ; (0-26.6)       / ± (5% of the reading + 0.1) ; (5% of the reading + 0.44)
  • 50 mm:     (0-1.2) ; (0-5)         / ± (5% of the reading + 0.02) ; (5% of the reading + 0.09)

  For detailed ranges and accuracies for NICO® click here 

Turbidity compensation: Yes

Data Logger: ~ 2 GB

 Reaction time T100: 20S

Measurement interval: ≥ 10 s

Housing material: Stainless steel (1.4571/1.4404) or titanium (3.7035)

Dimensions (L x Ø): ~ 470 mm x 48 mm (10 mm path); ~ 18.5“ x 1.9“ (with10 mm path)


  • stainless steel: ~ 3 kg (~ 6.6 lbs)
  • titanium: ~ 2 kg (~ 4.4 lbs)

Interface: digital: Ethernet (TCP/IP); RS-485 (Modbus RTU)

Power consumption: ≤ 7W

Power supply: 12...24 VDC (± 10 %)

Required supervision: Typically ≤ 0.5 h/month

Calibration/maintenance interval: 24 months

 System compatibility: Modbus RTU

Warranty: 2 years

 Max. pressure:

  • with Subconn: ~ 435 psig
  • with fixed cable: ~ 435 psig
  • in flow unit: ~ 14.5 psig at 0.5 to 1.0 gpm

 Protection type: IP68

 Sample temperature: +36 °F to +104 °F

 Storage temperature4 °F to +176 °F

Inflow velocity: 0.1...10 m/s (0.33 to 33 fps)

Accessories for NICO and OPUS

G2plus interface:

G2plus Rev2

# G2plus: G2plus interface

G2 interfacebox:

G2 interface box kit

11C100000: G2 interfacebox with WIFI

11C200000: G2 interfacebox without WIFI

11C000000: 2 G2 Interface Boxes without WiFi


Wiper W55:

Trios Wiper 55

02A100008: Wiper "W55 V2" is a mechanical wiper system for NICO and OPUS without wiper axis and wiper blades

Wiper blades: 

Wiper55 blades

     For W55 V2:

   # 02A100118  V2 Wiper blades set incl. wiper axis for 1mm path length

   # 02A100218  V2 Wiper blades set incl. wiper axis for 2mm path length

   # 02A100518 V2 Wiper blades set incl. wiper axis for 5mm path length

   # 02A100618 V2 Wiper blades set incl. wiper axis for 10mm path length

For W55 V1: 

     # 02A100108:Wiper blades set incl. wiper axis for 1mm path length

     # 02A100208:Wiper blades set incl. wiper axis for 2mm path length

     # 02A100508:Wiper blades set incl. wiper axis for 5mm path length

    # 02A100608:Wiper blades set incl. wiper axis for 10mm path length


Trios NICO Float

 # 05A000005: Mounting assembly for submerged        application Sensor float 


Trios Flowcell



 #10A100005: Flowcell 0.3 to 10mmm

  #10A100007: Flowcell 50mm

  #10A100013: Flowcell 0.3 to 10mmm with panel mount

  #10A100015: Flowcell 50mm with panel mount

Valtub (Calibration shell):


# 10A300000: VALtub 10 mm Cal. Shell

# 10A300001: VALtub 50 mm Cal. Shell


SID-12 Converter: 


11C100001: SDI-12 Coverter

Video: Lens socket change












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