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SYSTEM
When powered on, the ATMOS 41W measures the solar radiation once every 3 s and records
the instantaneous values. At the end of the measurement interval, the ATMOS 41W outputs
the average of the instantaneous values measured during that measurement interval.
NOTE: Calibration of the pyranometer is recommended every 2 years. Contact
for more information.
3.2.2 RAIN FUNNEL (PRECIPITATION)
The ATMOS 41W contains a 9.31-cm diameter rain funnel and two methods to measure
rainfall. During a rain event, precipitation first goes into the rain funnel where the spring
(
) acts as a filter to keep out large particles but still allows enough flow so water
does not back up. After flowing past the spring and into the rain gauge, precipitation flows
through the flared hole (
) to form drops of a consistent and known size that then
pass by the drop counter for the primary rainfall measurement.
The drop counter consists of two gold electrodes (
) that measure each drop formed
by the flared hole. Because the flared hole forms a drop of a known size, the ATMOS 41W
can calculate water volume from the number of drops counted. As the rain intensity
increases, the drops become smaller, but the ATMOS 41W firmware contains an algorithm to
automatically compensate for drop size as the intensity increases.
After passing the drop counter, the drops land in the tipping spoon reservoir for a secondary
rainfall measurement. The tipping spoon is precisely calibrated to tip with a highly-
repeatable water volume. Each time the spoon tips, a magnet passes a Hall-effect sensor
and the tip event is recorded.
The ATMOS 41W outputs the total rainfall (in millimeters) that has accumulated during
the measurement interval and the maximum intensity recorded over any individual 1-min
period during the measurement interval. The dual precipitation measurements allow the
ATMOS 41W to simultaneously measure rainfall with high resolution while maintaining
accuracy during high intensity events.
