Operation Manual

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Parameter Type of
Calibration
Default Typical Calibration Source
REL Barometer Offset Current Value Local airport (3)
ABS
Barometer
Offset Current Value Calibrated laboratory grade barometer
Wind Direction Offset Current Value GPS, Compass (4)
Temperature Offset Current Value Red Spirit or Mercury Thermometer (1)
Humidity Offset Current Value Sling Psychrometer (2)
Wind Gain 1.00 Calibrated laboratory grade wind meter (6)
Rain Gain 1.00 Sight glass rain gauge with an aperture of at
least 4” (7)
Solar Radiation Gain 1.00 Calibrated laboratory grade solar radiation
sensor
(1) The receiver 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.
(2) Only use this if you improperly installed the weather station sensor array, and did not point the direction
reference to true north.
(3) Temperature errors can occur when a sensor is placed too close to a heat source (such as a building structure, the
ground or trees).
To calibrate temperature, we recommend a mercury or red spirit (fluid) thermometer. Bi-metal (dial) and digital
thermometers (from other weather stations) are not a good source and have their own margin of error. Using a
local weather station in your area is also a poor source due to changes in location, timing (airport weather
stations are only updated once per hour) and possible calibration errors (many official weather stations are not
properly installed and calibrated).
Place the sensor in a shaded, controlled environment next to the fluid thermometer, and allow the sensor to
stabilize for 48 hours. Compare this temperature to the fluid thermometer and adjust the ObserverIP receiver to
match the fluid thermometer.
(4) 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.
(5) Wind speed is the most sensitive to installation constraints. The rule of thumb for properly installing a wind