Aercus Instruments™
- WeatherRanger®
39 |
P a g e
4.5.1 When To Calibrate And When Not To
SOUTHERN HEMISPHERE USERS!!!
For stations located in the
Southern Hemisphere
you must follow the southern hemisphere
wind recalibration instructions in Appendix 1 otherwise your wind direction readings will be
incorrect.
Note: The purpose of calibration is to fine tune or correct for any sensor error associated with the
device’s margin of error. Errors can occur due to electronic variation (example, the temperature
sensor is a resistive thermal device or RTD, the humidity sensor is a capacitance device), mechanical
variation, or degradation (wearing of moving parts, contamination of sensors).
Calibration is only useful if you have a known calibrated source you can compare it against, and is
optional. This section discusses practices, procedures and sources for sensor calibration to reduce
manufacturing and degradation errors. Do not compare your readings obtained from sources such as
the internet, radio, television or newspapers. The purpose of your weather station is to measure
conditions of your surroundings, which vary significantly from location to location.
4.5.2 Calibration Reference Table
Parameter
Type of
Calibration
Default
Typical Calibration Source
Temperature
Offset
Current Value Red Spirit or Mercury Thermometer (1)
Humidity
Offset
Current Value Sling Psychrometer (2)
ABS Barometer
Offset
Current Value Calibrated laboratory grade barometer
REL Barometer
Offset
Current Value Local airport (3)
Wind Direction
Offset
Current Value GPS, Compass (4)
Solar Radiation
Gain
1.00
Calibrated laboratory grade solar radiation
sensor
1 w/m
2
Gain
126.7 lux
Solar radiation conversion from lux to w/m
2
for wavelength correction (5)
Wind
Gain
1.00
Calibrated laboratory grade wind meter (6)
Rain
Gain
1.00
Sight glass rain gauge with an aperture of at
least 10cm (7)
Daily Rain
Offset
Current Value Apply an offset if the weather station was not
operating for the entire day.
Weekly Rain
Offset
Current Value Apply an offset if the weather station was not
operating for the entire week.
Monthly Rain
Offset
Current Value Apply an offset if the weather station was not
operating for the entire month.
Yearly Rain
Offset
Current Value Apply an offset if the weather station was not
operating for the entire year.
(1)
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
