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WS401-UMB Smart Weather Sensor

Make:  Lufft                              Model: WS401 UMB
✅ Compact all-in-one weather sensor, low power, aspirated radiation shield, open communication protocol.
✅ Measurand : Temperature, Relative humidity, Precipitation and Air pressure.
✅ Sensor Type : Compact weather station
✅ Signal Output : RS485 with supported protocols UMB-Binary, UMB-ASCII, Modbus-RTU, Modbus-ASCII, XDR and SDI-12.
✅ Article number:8377.U01

WS401-UMB Smart Weather Sensor:

From the WS product family of professional intelligent measurement transducers with digital interfaces for environmental applications. integrated design with ventilated radiation protection for measuring: air temperature, relative humidity, precipitation, and air pressure. One external temperature sensor is connectable.

Air Temperature and Humidity: Temperature is measured by way of a highly accurate NTC resistor, while humidity is measured using a capacitive humidity sensor. In order to keep the effects of external influences (e.g., solar radiation) as low as possible, these sensors are located in a ventilated housing with radiation protection. In contrast to conventional, non-ventilated sensors, this allows significantly more accurate measurement during high radiation conditions. Air temperature values with reduced accuracy are available as service channels for additional information. Additional variables such as dewpoint, absolute humidity, and mixing ratio are calculated from air temperature and relative humidity, taking account of air pressure.

Air Pressure: Absolute air pressure is measured by way of a built-in sensor (MEMS). The relative air pressure referenced to sea level is calculated using the barometric formula with the aid of the local altitude, which is user-configurable on the equipment.

Precipitation: Tried and tested radar technology from the R2S-UMB sensor is used to measure precipitation. The precipitation sensor works with a 24 GHz Doppler radar, which measures the drop speed and calculates precipitation quantity and type by correlating drop size and speed. WS401-UMB is using an unheated rain gauge for precipitation measurement. This version can be recommended for low-power applications, etc.

Note: Devices with precipitation radar are subject to approval regulations that differ between countries.

Application and features of WS401-UMB Smart Weather Sensor:



✅ Weather monitoring for measuring road and traffic control systems.
✅ Automatic weather station / Automatic weather sensor (AWS)
✅ PV-Monitoring / Solar Monitoring on photovoltaic farms
✅ Hydro-meteorological stations
✅ Weather observation for building automation
✅ Weather stations at airports, marinas and onboard ships
✅ Integration into various other systems/solutions, where these measurement parameters are needed.
✅ All-in-one housing design for a compact weather sensor that combines multiple measurement parameters in a single housing with only one cable connection.
✅ The first and only compact weather sensor with an integrated Kipp & Zonen CMP10 pyranometer and secondary quality standards.
✅ Built-in data pre-processing, universal interfaces, and selectable output protocols.
✅ Suitable for all climate zones and also for solar-powered automatic meteorological stations.
✅ WMO-recommended ventilation temperature and humidity measurement.





Ø ca. 150mm, height ca. 380mm

Weight (Mass)

Approx. 1.5 kg


RS485, 2-wire, half-duplex

Power Supply

4 ..11…32 VDC, 5…11 VDC (electronics with limited precision of measurements), 24 VDC +/- 10% (heater)

Power Consumption

40 VA (heater)

Operating Environment

Operating Temperature: -50…+60°C (with heater), Operating Rel. Humidity: 0…100% RH

Cable Length


Protection Level


Mast Diameter

60 – 76 mm

Air Temperature

Principle: NTC
Measuring range: -50 … +60 °C
Unit: °C
Accuracy: ±0.2°C (-20 … +50°C), otherwise ±0.5°C (>-30°C)

Relative Humidity

Principle: Capacitive
Measuring range: 0 … 100 % RH
Unit: % RH
Accuracy: ±2% RH

Air Pressure

Principle: MEMS capacitive
Measuring range: 300 … 1200 hPa
Unit: hPa
Accuracy: ±0.5 hPa (0…40°C)


Resolution: 0.2 mm
Accuracy: ±2 %
Max. intensity: 360 mm/h

Precipitation with reduction ring

Resolution: 0.5 mm
Accuracy: ±2 %
Max. intensity: 144 mm/h

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