NOTE:
To test the rain sensor before installation, slowly drip water into the funnel to mimic rainfall.
Pouring water too fast will get inaccurate pulse measurements.
5.2 Pyranometer
A silicon-cell pyranometer integrated into the lip of the rain gage funnel measures total
incoming (direct and diffuse) solar radiation. The pyranometer has a cosine-corrected head to
ensure accurate readings regardless of sun angle. Accurate solar radiation measurements require
the sensor to be level and clean.
5.3 Anemometer
An ultrasonic anemometer underneath the rain gage measures wind speed. Two pairs of
orthogonally oriented transducers emit ultrasonic signals that bounce off the porous sintered
glass plate and back up to the opposite sensor. The ClimaVUE 50 calculates wind speed by
measuring differences in the time it takes for sound to travel back and forth between the
transducers.
Wind speed and direction are measured every 10 seconds. The wind measurement takes 42
milliseconds followed by 60 milliseconds of processing. The processed speed and direction
outputs are vector averages. If an instantaneous measurement is more than eight times the
running average, the instantaneous measurement is rejected. It is not reported as the maximum
gust or included in the data that are averaged over the output interval.
5.4 Relative humidity sensor
The relative humidity sensor is located behind the circular Teflon® screen in the same housing as
the sonic transducers. The screen protects the sensor from liquid water and dust while allowing
water vapor to freely pass to the sensor. The sensor measures relative humidity and temperature
of the cavity, then uses those measurements to calculate vapor pressure. Vapor pressure doesn't
change with temperature, but relative humidity does. Because the true air temperature
(measured by the thermistor needle and corrected using wind and solar measurements) differs
from the cavity temperature, the true relative humidity is computed using the true air
temperature and the calculated vapor pressure.
ClimaVUE 50 Compact Digital Weather Sensor 8
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