User Manual

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(2) Humidity is a difficult parameter to measure electronically and drifts over time due to contamination. In
addition, location has an adverse affect on humidity readings (installation over dirt vs. lawn for
example).
Official stations recalibrate or replace humidity sensors on a yearly basis. Due to manufacturing
tolerances, the humidity is accurate to ± 5%. To improve this accuracy, the indoor and outdoor humidity
can be calibrated using an accurate source, such as a sling psychrometer.
(3) The display console displays two different pressures: absolute (measured) and relative (corrected to
sea-level).
To compare pressure conditions from one location to another, meteorologists correct pressure to
sea-level conditions. Because the air pressure decreases as you rise in altitude, the sea-level
corrected pressure (the pressure your location would be at if located at sea-level) is generally higher
than your measured pressure.
Thus, your absolute pressure may read 28.62 inHg (969 mb) at an altitude of 1000 feet (305 m), but
the relative pressure is 30.00 inHg (1016 mb).
The standard sea-level pressure is 29.92 in Hg (1013 mb). This is the average sea-level pressure
around the world. Relative pressure measurements greater than 29.92 inHg (1013 mb) are
considered high pressure and relative pressure measurements less than 29.92 inHg are considered
low pressure.
To determine the relative pressure for your location, locate an official reporting station near you (the
internet is the best source for real time barometer conditions, such as Weather.com or
Wunderground.com), and set your weather station to match the official reporting station.
(4) Only use this if you improperly installed the weather station sensor array, and did not point the direction
reference to true north.
(5) The default conversion factor based on the wavelength for bright sunlight is 126.7 lux / w/m
2
. This
variable can be adjusted by photovoltaic experts based on the light wavelength of interest, but for most
weather station owners, is accurate for typical applications, such as calculating evapotransporation
and solar panel efficiency.
(6) Wind speed is the most sensitive to installation constraints. The rule of thumb for properly installing a
wind speed sensor is 4 x the distance of the tallest obstruction. For example, if your house is 20’ tall
and you mount the sensor on a 5’ pole:
Distance = 4 x (20 – 5)’ = 60’.
Many installations are not perfect and installing the weather station on a roof can be difficult. Thus, you
can calibrate for this error with a wind speed multiplier.
In addition to the installation challenges, wind cup bearings (moving parts) wear over time.
Without a calibrated source, wind speed can be difficult to measure. We recommend using a calibrated
wind meter (available from Ambient Weather) and a constant speed, high speed fan.
(7) The rain collector is calibrated at the factory based on the funnel diameter. The bucket tips every 0.01”
of rain (referred to as resolution). The accumulated rainfall can be compared to a sight glass rain
gauge with an aperture of at least 4”.
Make sure you periodically clean the rain gauge funnel.
Note: The purpose of calibration is to fine tune or correct for any sensor error associated with the devices