Vaisala DRD11A Technical data

DRD11A

RAIN DETECTOR

©Kuvapörssi OY/Digital Vision

• Fast and accurate precipitation
detection (ON/OFF)

• Rain intensity measurement with
processing unit

• Maintenance free

• Heating element for keeping sensor
free of snow and condensed
moisture, and for quick drying

Rain and snow are quickly and accurately
detected with the DRD11A Rain Detector. The
DRD11A operates via droplet detection rather
than by signal level threshold.

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

The 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.
This design, together with the internal heating
element, ensures that the surface dries quickly,
an essential factor in calculating intensity. The
same heating element also protects the surface
from fog and condensed moisture, and is acti­vated at low temperatures in order to melt snow,
thus allowing snow detection. Sensor perfor­mance is not affected by reasonable amounts of
dirt and dust due to droplet detection.

The DRD11L is a low heating power model of
the DRD11A. It is intended to be used in areas
with only rain or wet/moist snow precipitation.

TECHNICAL DATA

SENSOR

Capacitive principle, thick layer sensor
RainCap™ with a thin glass shield. Integrated
heater element.

SENSITIVITY OF RAIN DETECTION

Minimum wet area 0.05 cm²
OFF-delay (active) < 5 min

PHYSICAL

Sensor plate

Sensing area 7.2 cm²
Angle 30°

Housing material Polypropylene
Windshield and support bracket Aluminum
Moisture shield Polyurethane
Dimensions (h × w × l)

With win d shield 110 × 80 × 175 mm
Without wind shield 90 × 46 × 157 mm

Weight 500 g
Cable length 4 m

ELECTRICAL

Supply voltage 12 VDC ± 10 %
Supply current

Typical less than 150 mA
Maximum 260 mA
Heater OFF 25 mA

Sensor plate

Heating power 0.5 ... 2.3 W

OUTPUT

Rain ON/OFF

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

INPUT

Control to switch heater OFF

Open circuit input enables the heater.

Connection to GND disables the heater.

Contact rating min. 15 V, 2 mA

GROUND WIRING

Separate ground wires for signal and heater

TEMPERATURE RANGE

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

MOUNTING

By one screw (M5 x 20 mm) to sensor arm.

Vaisala Oyj

P.O.Box 26
FIN-00421, Helsinki
FINLAND
Phone: [phone]
Telefax: ([phone]

B010018en-A