Intelligent Passive Road Sensor (IRS) for Accurate Road Measurements

The IRS31Pro-UMB passive road sensor is flush-mounted on the road. Due to the two-part housing design, the combined sensor/electronics unit can always be detached for maintenance or calibration.

The following parameters are measured:

  • Water film height up to 4 mm
  • Road surface temperature
  • Freezing temperature for numerous de-icing substances (NaCl, MgCl, CaCl)
  • Road condition (wet, damp, dry, ice or snow, damp with salt, wet with salt)
  • Friction (Grip)
  • Ice %.

Optional: Two additional depth temperatures, such as those at 5 cm and 30 cm. The measurement data is provided for additional processing through a standard procedure (Lufft UMB protocol).

  • Measurement technology: Measurements of conductivity (ice percentage), radar (water film), and NTC (road surface temp.)
  • Parameters measured: Water film height up to 4 mm, road surface temperature, freezing temperature for various de-icing materials (NaCl, MgCl, CaCl), road condition (wet, damp, dry, ice or snow, moist with salt, wet with salt), friction, ice %, and two more depth sensors
  • Product highlights: Low energy consumption allows for solar operation, and the two-part housing design simplifies maintenance and calibration. Additionally, the radar principle measures water film
  • Interfaces: RS485, SDI-12, analog outputs
  • Article number: 8910.U050, 8910.U051, 8910.U052, 8910.U100, 8910.U101, 8910.U102


  • Polling via RS485 interface
  • Analog outputs in combination with a converter (DACON-8160.UDAC)
  • Radar principle to measure water film
  • Freezing temperature output starts at a dry-damp threshold that has been established (for example, 10 m in accordance with the new TLS specification)
  • Replaceable sensor electronics (for easy calibration or maintenance)

Examples of Use

  • It was installed on the runway as a crucial component of the IDS (ice detecting system) and water film height detection at airports (aqua-planning risk)
  • For winter maintenance personnel working with road weather stations on roads, highways, and freeways (municipalities, federal states, and provinces)
  • For smart cities


  • Product calibration
  • SmartView3
  • Software collector
  • Digital-Analog-Converter DACON8-UMB
  • Spare part cap (IRS31Pro-UMB)
  • Calibration kit IRS-31UMB
  • ViewMondo-Road & Runway Management Software

Technical Data

Source: OTT HydroMet-Meteorology

Measuring parameters  
Road Conditions Dry/moist/wet/moist with salt/wet with salt/ice, snow, frost
Sampling rate 10 … 60 seconds
Road surface temperature & below ground temp.
Principle NTC
Measuring range -40 ... 80 °C
Accuracy ±0.1 °C (-20 ... 20 °C), otherwise ±0.2 °C
Resolution 0.02 °C (-20…+20), otherwise 0.1
Freezing point  
Measuring range -40 ... 0 °C
Accuracy ±0.5 °C (0 ... -2.5 °C), else ±20% of average value (with de-icing agent NaCI)
Resolution 0.1
Water film height  
Principle Radar
Measuring range 0 ... 4000 µm
Accuracy 200 µm <3 mm, otherwise +/-30%
Resolution 10 µm
Friction (Grip)  
Measuring range [slippery...dry] 0 ... 1
Ice Percentage  
Measuring range 0 ... 100 %
Resolution 0,10%
Standard interfaces (out) RS485 or SDI-12, 2 wire, half dublex
Baud rates 1200, 2400, 9600, 19200, 38400
Communication Protocols UMB, SDI-12
Connector cable wires 0.5 mm²
Electrical parameters  
Power supply 9-14 VDC, nominal 12V
Power consumption (typ.)  
Protection class III (SELV)
Operating Conditions  
Operating temperature -40 … 80 °C
Ambient storage temperature -40 … 70 °C
Relative humidity (ambient) 0 … 100 %
Relative humidity storage 0 … 95 % (non-condensing)
Operating altitude -500 … +3000 m
Safety and compliance  
Protection level housing IP68
Electrical Safety EN 61010-1:2011-07
Electromagnetic Conformity IEC 61326 – 1:2012
Certifications CE, FCC
Surface condition standard EN 15518-3:2011 tests carried out regarding CEN/TS 15518-4:2013
Dimensions Ø 120 mm, height 50 mm
Weight Approx. 800 g without cable and without an external temperature probe

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