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Enabling better global research outcomes in soil, plant & environmental monitoring.

RF4 Acoustic RainFlow Sensor

The RF4 Acoustic RainFlow sensor from ISAW in Switzerland is a robust and zero-maintenance rain sensor. Capable of measuring rain and hail precipitation, as well as high-resolution disdrometry (number and size of raindrops), the RF4 RainFlow sensor is ideal for comprehensive measurements of the type, amount, intensity and structure of liquid and solid precipitation.

The design of the sensing unit ensures that it is unable to be obstructed – the stainless steel hemispherical dome prevents build up of dust or debris and ensures that the sensor is unobstructed.

With no moving parts as it is a totally sealed acoustic instrument, the RF4 RainFlow sensor is zero maintenance, ideal for installation in remote locations.

Constructed to be resistant to the highest winds and most extreme conditions, the RF4 RainFlow sensor is corrosion resistant and UV stable due to the use of stainless steel in the hemispherical dome.

Low power consumption (less than 2.1mA for a 10% duty cycle) and compatibility with a range of output signals enables the connection with ICT International IoT Nodes to enable use in IoT monitoring systems.


Measuring surface 160 mm outer diameter hemisphere (402 cm2)
Precipitation detected by the sensor Liquid (undifferentiated): rain, drizzle/rain, mixed rain/snow, sleet.
Solid: hail.
Rain Intensity accuracy +/-15% at 100% duty-cycle (most global precision and accuracy criteria)
Rain DSD 27 classes from ≤ 0.75 mm to +/- 7.0mm with a detection threshold (minimum detectable diameter) of about 0.5 mm
Measurement accuracy (liquid only) A spatially distributed flux of controlled drops of a nominal diameter equal to the centre diameter of the class ± 20% produces an output centred in the corresponding class with typically +/- 50% of the flux concentrated into the two lateral size-classes.
Hail detection* Counting of the number of hailstone impacts up to 5 impacts per second and for hailstone diameter detection threshold of 0.5 cm.
Particle velocity Not measured.
*Note: For more specific hail detection, use the HailFlow HF4 sensor, variant of the RF4 specialized in hail detection.