Calibration Discussion - Ambient Weather WH2902 User Manual

Parameter
Indoor Temperature
Indoor Humidity
Outdoor Temperature
Outdoor Humidity
Absolute Pressure
Wind Direction
Wind Speed Factor
Rain Factor

6.10.3 Calibration Discussion

The purpose of calibration is to fine tune or correct for any sensor error associated with the devices
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.
Parameter Type of
Calibration
Temperature Offset
Humidity Offset
ABS Offset
Barometer
REL Barometer Offset
Wind Direction Offset
Wind Gain
Rain Gain
(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 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 console to match the fluid thermometer.
Version 1.0
Range
± 9 °F
± 9%
± 9 °F
± 9%
± 10 hpa (± 2.95 inHg)
± 180 °
0.5 to 1.5
0.5 to 1.5
Figure 21
Default
Current Value Red Spirit or Mercury
Current Value Sling Psychrometer (2)
Current Value Calibrated laboratory grade
Current Value Local airport (3)
Current Value GPS, Compass (4)
1.00 Calibrated laboratory grade
1.00 Sight glass rain gauge with an
Figure 22
Typical Calibration Source
Thermometer (1)
barometer
wind meter (5)
aperture of at least 4" (6)
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