METER ATMOS 41 - 3.3 ANEMOMETER

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ATMOS 41
Spectral response was estimated by multiplying the spectral response of the photodiode,
diffuser, and adhesive. Spectral response measurements of diffuser and adhesive were
made with a spectrometer, and spectral response data for the photodiode were obtained
from the manufacturer.
Leveling the ATMOS 41 is particularly important for accurate solar radiation measurements.
Out of level, the pyranometer will overestimate some portions of the day while under-
estimating others. Ensure accurate solar radiation measurements by carefully leveling the
ATMOS 41 at installation. Bird droppings and other soiling of the domed sensor surface will
cause serious errors in pyranometer measurements. Check the sensor regularly to make sure
it is clean and check data often to identify possible problems. Isopropyl (rubbing) alcohol and
a Q-tip work well for cleaning the sensor area. Microfiber bags work well, too. Do NOT use an
abrasive cloth on the sensor surface, as it will scratch.
The pyranometer is factory calibrated and the sensor-specific calibration value can be found
on the interior of the rain funnel. This factor has already been added into the ATMOS41 so
there is no need to do anything with it. In the event that this value is needed, it can be found
by taking the funnel off the base and checking underneath. Follow the steps in Section 3.5 to
remove the funnel.
When powered on, the ATMOS41 measures the solar radiation once every 10 s and
records the instantaneous values. When queried, the ATMOS41 outputs the average of the
instantaneous measurements since the last query.
3.3 ANEMOMETER
The space underneath the rain gauge is where the ATMOS41 measures wind speed.
Ultrasonic signals emitted from transducers at right angles to each other bounce off
the porous sintered glass plate (Figure7) and back up to the opposite sensor. The
speed ofsound is affected by the wind, and the wind speed is calculated by measuring
differences in the time it takes for sound to travel back and forth between sensors
(Section3.10.1).
When powered on, the ATMOS41 measures the wind speed and direction once every 10 s and
records the instantaneous wind vector components. When queried, the ATMOS41 outputs
the average of the instantaneous measurements since the last query for wind speed and
direction and the maximum instantaneous wind speed value for wind gust.