RG-11 Optical rain gauge

RG-11 optický srážkoměr

RG-11 is an optical rain gauge-rain intensity detector, with simulated pulse output, simple mechanical construction and sophisticated software.

Measurement principle

The principle of measuring precipitation is based on the continuous evaluation of the intensity of 4 reflected infrared rays from water-soaked transparent spherical cover of a sensor with a diameter of 70 mm.

RG-11 princip optického srážkoměru

The control electronics of the sensor is able to evaluate even drops with a size of 0.5 mm and at the same time eliminates ambient light changes, the effect of adhering dirt and aging of the sensor surface.


The method used to evaluate the amount of rainfall is very sensitive and allows you to set in addition to the standard output 0.2 mm rainfall / pulse and 0.01 mm and even in the most sensitive mode and 0.001 mm rainfall / pulse.

However, the high sensitivity of the sensor does not mean absolute measurement accuracy and therefore this device cannot fully replace well-maintained shuttle or weight rain gauges in applications requiring accurate measurement under various operating and weather conditions, but is suitable as a suitable complement to such measurement due to high resistance and reliability of this sensor. . This is achieved due to the absence of mechanical moving parts and in conjunction with the glossy spherical surface of the sensor, which prevents dirt or fallen leaves from settling.

Comparison of RG-11 with shuttle rain gauge

The following two graphs show comparative graphs between the SR03 shuttle rain gauge with a collection area of 500 cm2 and between the RG11 optical rain gauge, which took place in summer and autumn 2017 at the meteorological station of the Institute of Hydrodynamics of the ASCR.

The graphs show a better ability of the shuttle rain gauge to record higher precipitation intensities. On the other hand, in the total precipitation, both devices are practically comparable.


Precipitation intensity 2017: 

RG-11 optický srážkoměr - graf


Precipitation total 2017:

RG-11 optický srážkoměr - graf

Technical parameters

The pulse output of the sensor consists of a relay contact and can be connected to all FIEDLER stations similarly to the output of shuttle rain gauges. However, the RG-11 device, unlike shuttle rain gauges, requires the permanent presence of a supply voltage of 10-15 V (type 12V). However, the quiescent current consumption of 12V / 15 mA, which can increase up to 70mA in the rain, does not allow the connection of this interesting sensor to stations powered only by the battery.

RG-11 is installed in a horizontal position on a boom with a width of max 19.6 mm.

Other uses for RG-11

In addition to the pulse output, the user-adjustable sensor mode also allows a permanently closed contact in the rain (adjustable rain intensity to close the contact), detection of condensed water and icing on the sensor surface, irrigation control and drop detection. The sensor mode and its parameters are selected by switches inside the sensor.

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