Key features


  • All-in-one housing concept of a compact weather sensor combining several measurement parameters in one housing with only one cable connection
  • Integrated Kipp & Zonen CMP3 Pyranometer, which is tiltable
  • Built-in data pre-processing, universal interfaces and selectable output protocols
  • Maintenance-free operation – no moving parts that can wear out
  • Compatible with many commercially available Met/HydroMet data loggers and PLS systems thanks to an open communication protocol
  • Suitable for all climate zones; also for solar-powered automatic meteorological stations
  • Ventilated temperature and humidity measurement according to WMO guidelines
  • Integrated heater that can be switched on if there is danger of frost


The WS303-UMB Smart Weather Sensor for measuring of air temperature, relative humidity, solar radiation, and air pressure. Relative humidity is measured by means of a capacitive sensor element; a precision NTC measuring element is used to measure air temperature. The world renowned technology of Kipp & Zonen CMP3 is integrated. Measurement output can be accessed by the following protocols: UMB-Binary, UMB-ASCII, SDI-12, MODBUS. One external temperature or rain sensor is connectable.

Lufft WS303-UMB

  • Temperature

    Principle NTC
    Measuring Range -50...60°C
    Accuracy ±0,2°C (-20°C...+50°C), otherwise ±0.5°C (>-30°C)

    Relative Humidity

    Principle Capacitive
    Measuring Range 0...100% RH
    Accuracy ±2% RH


    Response Time (95%) < 18s
    Non-stability (change/year) < 1%
    Non-linearity (0 to 1,000 W/m²) < 1%
    Directional error (at 80° with 1,000 W/m²) < 20 W/m²
    Temperature dependence of sensitivity < 5% (-10 bis 40°)
    Tilt error (at 1000 W/m²) < 1%
    Spectral range (50% points) 300 to 2,800nm
    Measuring range 1400 W/m²
    Altitude 0...60°
    Azimuth -10°...10°

    Air Pressure

    Principle MEMS Capacitive
    Measuring Range 300...1200 hPa
    Accuracy +/- 0.5 hPa (...+40°C)

    General Information

    Heating 20VA at 24VDC
    Interface RS485, 2-wire, half-duplex
    Operating Power Consumption 4....32 VDC
    Operating Humidity Range 0...100%
    Operating Temperature Range -50...60%°C