Rain Detector DRD11A

Fast and accurate precipitation and intensity measurement

Model: DRD11A
Manufacturer: Vaisala – Finland


  • Fast and accurate precipitation detection (ON/OFF)
  • Rain intensity measurement with processing unit
  • Heating element for keeping sensor free of snow and condensed moisture, and for quick drying
  • Maintenance free

Vaisala DRD11A Rain Detector detects rain and snow quickly and accurately. It uses droplet detection instead of signal level threshold.


A delay circuitry allows a two-minute interval between raindrops before assuming the OFF position (no rain). This enables the sensor to accurately distinguish between rain cessation and light rain.

DRD11A also features an analog rain signal for estimating rain intensity. Since this signal is proportional to the percentage of moist or wet area on the sensor plate, rain intensity has a direct impact on the amplitude and variation of this analog signal.

The DRD11A sensor is positioned at a 30° angle. The design together with the internal heating element ensure that the surface dries quickly. This is an essential factor for calculating intensity. The same heating element also protects the surface from fog and condensed moisture. It activates at low temperatures to melt snow and allow snow detection. Sensor performance is not affected by reasonable amounts of dirt and dust due to droplet detection.

The low heating power model DRD11L is designed for areas with only rain or wet and moist snow precipitation.

Measurement Performance

Sensor Capacitive principle, thick layer sensor RAINCAPâ, with a thin glass shield Integrated heater element
Rain Detection Sensitivity
Minimum wet area 0.05 cm2 (0.008 in2 )
Detection delay < 0.1 ms
OFF delay (active) < 5 min
Precipitation Type Identification
DRD11A only Rain
When air temperature and relative humidity are available Rain, Sleet/Mixed, Snow
Sensor Plate
Sensing area 7.2 cm2 (1.12 in2 )
Angle 30°


Inputs and Outputs


Operating voltage 12 VDC ±10 %
Average power consumption 0.30 W at 12 V
Maximum power consumption with sensor plate heating on 3.12 W at 12 V 1)
Rain on/off output Open collector, active low signal corresponds to rain 

Maximum voltage 15 V 

Maximum current 50 mA

Analog output 1 … 3 V (wet … dry) 
Frequency output 1500 … 6000 Hz, non-calibrated
Supply current Typical less than 150 mA 

Maximum 260 mA 

Heater off 25 mA

Heating power, sensor plate 0.5 … 2.3 W
OFF Connect to GND
Contact rating Minimum 15 V, 2 mA


1) The actual power consumption depends on the temperature and rain intensity


Mechanical Specifications


Dimensions (H × W × L) With wind shield: 110 × 80 × 175 mm 

(4.33 × 3.15 × 6.89 in) 

Without wind shield: 90 × 46 × 157 mm 

(3.54 × 1.81 × 6.18 in)

Weight 0.5 kg (1.1 lb)
Cable length 4 m (13 ft 1 in)
Ground wiring Separate ground wires for signal and heater
Mounting By one screw (M5 x 20 mm) to sensor arm
Housing Polypropylene
Windshield and support bracket Aluminum
Moisture shield Polyurethane 


Operating Environment


Operating temperature -15 … +55 °C (+5 … +131 °F)
Storage temperature -40 … +65 °C (‑40 … +149 °F)

Rain Detector DRD11A Datasheet


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