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Measuring weather
Other hygrometers
Electrical hygrometers use moisture sensitive, conductive polymer films that measure changes in capacitance or resistance that occur in along with changes in moisture.
Gravimetric hygrometers are the most accurate moisture measuring
instrument, but they tend to be inconvenient and time-consuming. Therefore,
they are typically only used for calibration of other instruments. A
gravimetric hygrometer compares the mass of an air sample to the mass of a dry
sample of air having the same volume. The difference is the mass of water vapor
in the air.
A Sling Psychrometer consists of a dry bulb thermometer, a wet bulb
thermometer, and a handle for whirling the thermometers
around in a circle. As water from the moistened bulb absorbs energy
and evaporates, the wet bulb temperature decreases. The two
stabilized temperatures can be used to compute the dew point temperature.
Hygrographs use a hygroscopic material sensor, such as synthetic fiber,
hair, or salt paper, mechanically linked to a pen or dial by a spring mechanism.
As the humidity changes, the sensor expands or contracts, changing the position
of the pen arm or dial recording the result on paper.
Knowledge of humidity measurements has many practical applications. Among these
are precipitation, cloud, fog, dew, and frost formation, and initialization of
forecast models.
Next page
->
in situ, surface observations, wind
Links and resources
Other hygrometers
Electrical hygrometers use moisture sensitive, conductive polymer films that measure changes in capacitance or resistance that occur in along with changes in moisture.
Gravimetric hygrometers are the most accurate moisture measuring
instrument, but they tend to be inconvenient and time-consuming. Therefore,
they are typically only used for calibration of other instruments. A
gravimetric hygrometer compares the mass of an air sample to the mass of a dry
sample of air having the same volume. The difference is the mass of water vapor
in the air.
A Sling Psychrometer consists of a dry bulb thermometer, a wet bulb
thermometer, and a handle for whirling the thermometersaround in a circle. As water from the moistened bulb absorbs energy
and evaporates, the wet bulb temperature decreases. The two
stabilized temperatures can be used to compute the dew point temperature.
Hygrographs use a hygroscopic material sensor, such as synthetic fiber,
hair, or salt paper, mechanically linked to a pen or dial by a spring mechanism.
As the humidity changes, the sensor expands or contracts, changing the position
of the pen arm or dial recording the result on paper.
Knowledge of humidity measurements has many practical applications. Among these
are precipitation, cloud, fog, dew, and frost formation, and initialization of
forecast models.
Next page
->
in situ, surface observations, windLinks and resources
