Meteorological Instruments

4. Six's thermometer is a
registering thermometer which can record the
maximum reached over a period of time. It is used to
record the extremes of temperature at a location. It
was invented by Englishman
James Six in 1782. The thermometer indicates the
current temperature and the highest and lowest
temperatures since last reset. It consists of a U-
shaped glass tube
with two separate
temperature scales set
along each arm of the U.
One of these is for
recording the maximum
temperature and the other
for the minimum temperature. Bulbs of thermometer

5. The bulb at the top of the
m minimum reading scale
arm arm is full of alcohol, the othe
other contains a vacuum mer mercury.
This is pushed arou around the tube
the b by thermal expansion and
contraction of the alcohol in the first bulb as it
responds to the external temperature. It is the
alcohol which measures the temperature; the
mercury indicates the temperature reading on both
scales. The maximum and minimum readings are
recorded by two small steel markers which are
sprung into the capillary tube so that they can slide.
Maximum temperature showed

6. Uses
Six's maximum and
minimum thermometer
record the maximum
and minimum temperature
reached since the
thermometer was read.
It is a popular thermometer among gardeners for
use in greenhouses. It is interesting to note that
Six's maximum and minimum thermometers were
still being used in 2000 of exactly the
same design and construction as ones produced
over 100 years ago. Typically the thermometer is
reset every 24 hours to measure the diurnal
temperature variation.
Minimum & maximum temperature

8. A mercury barometer has a glass tube with a height
of at least 84 cm, closed at one end, with an open
mercury-filled reservoir at the base. The weight of
the mercury creates a vacuum in the top of the tube.
Mercury in the tube adjusts until the weight of the
mercury column balances the atmospheric force
exerted on the res
reservoir. High atmospheric p
pressure places more force on on the
reservoir, forcing mer mercury higher
in the column column .
Various types of mercury barometer

9. Low pressure allows the mercury to drop to a lower
level in the column by lowering the force placed on
the reservoir. It was invented by Torricelli who
documented that the height of the mercury in a
barometer changed slightly each day and concluded
that this was due to the changing pressure in
the atmosphere. Since higher temperature levels
around the instrument will
reduce the density of the
mercury, the scale for
reading the height of the
mercury is adjusted to
compensate for this effect.
Simple mercury barometer

10. Uses
The mercury barometer's design gives rise to the
expression of atmospheric pressure in inches or
millimeters or feet (torr ).Typically, atmospheric
pressure is measured between 26.5 to 31.5 inches
of Hg. One atmosphere (1 atmospheric pressure) is
equivalent to 760 millimeters of mercury.
It is also used to interpret
the changing pressure.
Goethe’s Device

12. An aneroid barometer is
an instrument for
measuring pressure
as a method that does
not involve liquid.
Invented in 1844 by
French scientist Lucien
Vidi, the aneroid barometer uses a small, flexible
metal box called an aneroid cell (capsule), which is
made from an alloy of beryllium and copper. The
evacuated capsule (or usually more capsules) is
prevented from collapsing by a strong spring. Small
changes in external air pressure cause the cell to
expand or contract.
Old Aneroid Barometer

13. This expansion and
contraction dr drives mechanical
levers such th at the tiny
movements of the cap capsule are
amplified and display displayed on the
face of the aner aneroid
barometer. Many mod models
include a manually set n
needle which is used to mark the current
measurement so a change can be seen. In addition,
the mechanism is made deliberately "stiff" so that
tapping the barometer reveals whether the
pressure is rising or falling as the pointer moves.
Barometer of 1890’s

15. A weather vane, wind vane,
or weathercock is an
instrument for showing
the direction of the wind.
They are typically used as
an architectural ornament
to the highest point of a
building. Although partly
functional; weather vanes are generally decorative,
often featuring the traditional cockerel design with
letters indicating the points of the compass. Other
common motifs include ships, arrows and horses.
Not all weather vanes have pointers. The word
'vane' comes from the Old English
word fana meaning 'flag’.
A Wind vane

16. Early weather vanes had very ornamental pointers,
but modern wind vanes are usually simple arrows
that dispense with the directional because the
instrument is connected to a remote reading
station. Modern aero vanes combine the directional
vane with an anemometer (a device for measuring
wind speed). Co-locating both instruments allows
them
to use the same axis
(a vertical rod) and
provides a
coordinated readout.

17. Uses
Wind vanes are ancient instruments, with their use
recorded all the way back to the Roman Empire.
Consisting of a simple design, wind vanes
give onlookers an instant
appraisal of wind direction.
Farmers used wind vanes
for centuries and, although
they have been largely
replaced with more
modern devices in a function sense, wind vanes still
provide decoration and an indication of which way
the wind is blowing.

19. An anemometer or wind meter is a device used for
measuring wind speed, and is a common weather
station instrument. It is derived from the Greek
word anemos, meaning wind, and is used to
describe air speed measurement instrument used in
meteorology or aerodynamics. Leon Battista
Alberti is said to have invented the first
mechanical anemometer
around .There are many
types of anemometer namely
-Cup anemometers, Vane
anemometers, Hot-wire
anemometers, Laser Doppler ,
Ping-pong ball anemometers,
Plate anemometers and Tube anemometersHemispherical cup anemometer

20. The effects of the terrain needs to be considered,
especially in regard to height. Other considerations
are the presence of trees, and both natural canyons
and artificial canyons . The standard anemometer
height in open rural terrain is 10 meters. In the tube
anemometer the pressure is measured, although the
scale is usually graduated as a velo
velocity scale. In cases where t the
density of the air is signific significantly
different from th the calibration
value an allow allowance must be made.
A Approximately 1 1⁄2% should be a
added to the velocity recorded by
by a tube anemometer
Vane anemometer

22. A rain gauge is a type of Instrument used
by meteorologists and hydrologists to gather and
measure the amount of liquid precipitation over a
set period of time. George James
Symons found the first
systematic rainfall survey.
Rain gauge amounts are read
either manually or by weather
station AWS The frequency of
readings will depend
on the requirements of the
collection agency. Some countries will supplement
the paid weather observer with a network of
volunteers to obtain precipitation data for sparsely
populated areas..
Plastic rain gauge

23. For virtually any gauge,
drops will stick to the sides
or funnel of the collecting
device, such that amounts
are very slightly and those
of .01 inches or .25 mm may
be recorded as a trace. Rain
may fall on the funnel and ice or snow may collect
in the gauge, blocking subsequent rain. Rain gauges
should be placed in an open area where there are
no obstacles, such as buildings or trees, to block
the rain. This is also to prevent the water
collected on the roofs of buildings or the leaves of
trees from dripping into the rain gauge after a
rain, resulting in inaccurate readings
Tipping bucket rain gauge

25. A hygrometer is an instrument used for measuring
the moisture content in the atmosphere. Humidity
measurement instruments usually rely on
measurements of some other quantity such as
temperature, pressure, or electrical change in a
substance as moisture is absorbed. By calibration
and calculation, these measured quantities can lead
to a measurement of humidity. Use of temperature
of condensation
or changes in electrical
capacitance or resistance
to measure humidity
differences is common.
It was invented by
polymath Johann Heinrich Lambert in 1755 .
Dial
hygrometer

26. The humidity level in a home is typically between
30 and 50 percent. Humidity measurement is
among the more difficult problems in basic
meteorology. Hygrometers must be calibrated in
air, which is a less effective heat transfer medium
than is water, and many types are subject to
drift so need regular recalibration. A further
difficulty is that most hygrometers sense relative
humidity rather than
the absolute amount of
water present, but relative
humidity is a function of
both temperature and absolute
moisture content.
A detailed psychrometer
In a Stevenson screen