The Hygrometer
The hygrometer is the first known device used for measuring the
humidity in the air (Michael Carlowicz, 2011). The first crude hygrometer was
built in the 1400’s by Leonardo Da Vinci. However, Francesco Folli invented a
more practical hygrometer in 1664 (Hile, 2009).
humidity in the air (Michael Carlowicz, 2011). The first crude hygrometer was
built in the 1400’s by Leonardo Da Vinci. However, Francesco Folli invented a
more practical hygrometer in 1664 (Hile, 2009).
What does the Hygrometer do?
The hygrometer measures the temperature at which dew or frost forms, which is a
measure of the absolute humidity—the weight of water vapor per unit volume of
air or other gas at the temperature before cooling (The Columbia Encyclopedia, 2012).
measure of the absolute humidity—the weight of water vapor per unit volume of
air or other gas at the temperature before cooling (The Columbia Encyclopedia, 2012).
The Psychrometer
The psychrometer, which is also the most common type of hygrometer, is the dry and
wet bulb consisting of two identical mercury or electrical thermometers, one of
which contains wet cotton or a linen wick (The Columbia Encyclopedia, 2012).
Evaporating water from the wick absorbs heat from
the thermometer bulb, causing the thermometer reading to drop (The
Columbia Encyclopedia, 2012). In general, the drier the air, the greater is the drop in temperature.
The relative humidity is determined by comparing the readings of the two
thermometers with published psychrometric tables or charts ("Hygrometer,"
2012).
wet bulb consisting of two identical mercury or electrical thermometers, one of
which contains wet cotton or a linen wick (The Columbia Encyclopedia, 2012).
Evaporating water from the wick absorbs heat from
the thermometer bulb, causing the thermometer reading to drop (The
Columbia Encyclopedia, 2012). In general, the drier the air, the greater is the drop in temperature.
The relative humidity is determined by comparing the readings of the two
thermometers with published psychrometric tables or charts ("Hygrometer,"
2012).