What is humidity?
Humidity (relative humidity) can be expressed as the
amount of water vapor present in the air expressed as a percentage of the
maximum air load of water vapor at that Celsius temperature at which the
humidity was measured. For example, air can carry an estimated 2.2 grams of
water vapor per A cubic meter at a temperature of ten below zero. If we find at
that temperature an estimated 1.1 grams of water vapor per cubic meter, we can
say that the humidity in the air is equivalent to fifty percent.[1]
How to measure humidity in the air
The humidity rate in the air can be measured using a
device called a psychrometer or hygrometer, which uses two temperature sensors,
one of which measures the dry temperature and the other measures the wet
temperature, where the wet temperature sensor contains a quantity of water in
its base to evaporate and absorb heat. Which would reduce the temperature, and
in order to be able to measure the relative humidity, it is necessary to take
the readings of the two sensors (dry and wet) and find the difference between
them, and the device (the cyclometer) should be hung in the open air until its
reading is proven and recorded.[2]
Humidity effect
The effect of humidity reaches all living organisms on the
face of the globe to the extent of affecting the growth of plants and animals
alike. As for man, he depends on getting rid of excess heat on the natural
process of sweating, but during exposure to high humidity environments, the
rate of evaporation of sweat decreases as it depends The rate of blood pressure
depends on how much the body gets rid of the excess heat inside it through
sweating, causing a state of high body temperature (hyperthermia). All of what
was mentioned, the effect of humidity reaches even electronic devices and
industrial equipment in general. [3]
Humidity measurement methods
1. Psychrometer
It is a device that consists of two thermometers, one of
which is dry and the other is wet. Humidity is measured by comparing the two
temperatures indicated by the two scales. This device is considered one of the
simplest methods used to measure humidity.
Suspended Psychrometer: Also known as rotary, which
consists of two thermometers, one dry and the other wet, are installed inside a
metal frame with a rotating hand to move it manually, in a circular and quick
way to obtain the necessary ventilation, and this is done by holding the hand
on the device, raising it above the head and then Rotate it several times, and
the humidity is determined by measuring two successive ventilation readings,
after which the humidity is determined according to the psycrometer tables.
Psychrometer: It is similar to a suspended
psycrometer, as it contains dry and wet calibers, except that the ventilation
process does not occur through a manually operated fan, but is driven by an
electric motor, so an air current is generated to measure the humidity.
2. Capillary hygrometer
It is also called a hygrometer. This device consists of a
group of hair tufts that may be human or horse; Because the hair expands when
humidity increases and contracts when it decreases, and a feather is installed
at the end of these tufts, which moves in front of a ruler with numbers from
zero to one hundred.
3. Relative humidity meter
It is also called a hygrograph, where the principle of the
relative hygrometer is based on a similar principle to the capillary
hygrometer. From the levers that transfer it to the tip of the feather, which
in turn draws the ratio on a twisted diagram on a cylinder that moves in a
fixed rate, and the hygrometer is placed in the inside of the monitoring cage.
4. Thermometer and relative humidity
It is a device that measures and records the temperature
and relative humidity on the cylinder itself, and relies on a heat-sensitive
metal ring. As for the measurement of temperature, it uses a strand of hair.
Hygrometer
Humidity can be measured through a device known as a
hygrometer, and this device has many different types, and here are some of
these types:[4]
1. Mechanical hygrometer
Humidity is measured through a mechanical hygrometer
through the use of some micro-organic materials, such as human hair, where a
hair from the human head is fixed on a pointer in the measuring device, and
this hair expands or contracts according to the amount of moisture it is
exposed to, which leads to a change in the indicator , to measure the degree of
humidity.
2. Electronic hygrometer
Humidity can be accurately measured through the use of an
electronic hygrometer, which is based on the principle of changing electrical
resistance; Where two types of metal plates are exposed to moist air, and the
higher the humidity, the greater the ability of those plates to store
electrical charges, then the amount of charges that were stored in the plates
is calculated.[5]
3. Cyclometer
The Psychrometer consists of two thermometers, one dry and
the other covered with a piece of wet cloth, and the temperature of the wet
scale is lower than the temperature of the dry one, due to the coldness
produced by the evaporation of water, then the difference between the two
temperatures is calculated in the scale to extract the moisture content [6]
The importance of measuring humidity
Humidity is defined as the amount of water vapor present
in the air,[7] and the measurement of humidity is extremely important in our
daily lives, apart from its connection to weather forecasts, and this
importance is as follows:[8]
1.
Human and animal health: Increasing
humidity in the air negatively affects human health, and can result in cases of
heat stress or breathing problems, and the danger of humidity is not limited to
humans, as it also affects animals such as problems in reproduction and
increased mortality rates.
2.
Precipitation: The amount of
water vapor in the air affects the amount of precipitation.
References
1.
"Humidity",
www.nationalgeographic.org, Retrieved 8-12-2018. Edited.
2.
"Instruments",
climate.ncsu.edu, Retrieved 26-11-2018. Edited.
3.
Benjamin Elisha Sawe (25-4-2017),
"What
Is Humidity And How Does It Affect Life On Earth?"، www.worldatlas.com, Retrieved 26-11-2018. Edited.
4.
"Hygrometer",
www.britannica.com, Retrieved 22-1-2019. Edited.
5.
Chris Woodford. (14-7-2018),
"Hygrometers"، www.explainthatstuff.com, Retrieved 22-1-2019. Edited.
6.
"Psychrometer",
www.encyclopedia.com, Retrieved 22-1-2019. Edited.
7.
"What
Is Humidity And How Does It Affect Life On Earth?",
www.worldatlas.com, Retrieved 23-1-2019. Edited.
8.
"Why
is humidity important?", www.metoffice.gov.uk, Retrieved 06/06/2022.
Edited.
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