The document discusses various instruments used to measure atmospheric pressure, including barometers, manometers, and pressure altimeters. A barometer typically uses mercury to determine pressure, while a u-tube manometer compares the densities of two liquids. Additionally, pressure altimeters measure altitude based on atmospheric pressure changes, with applications in aviation and diving.

1. GROUP # 03
JAMAL UD DIN 11
M.SALMAN 12
NOMAN HILAL 13
M.ZEESHAN AHMAD 14
M.ANWAR 15

2. BAROMETER
• Instrument used for measuring atmospheric
pressure is called barometer or mercury
barometer
• A simple barometer consist of glass tube
having length equal to about 80cm
• It is open on one side while its other side is
closed
• First it is filled with mercury and is then
inverted in small reservoir full of mercury

3. Dimension
• The atmospheric pressure acting on the
surface of mercury in the reservoir support a
column of mercury in the tube
• The height h of the column
of the mercury is about
760mm for the standard
temperature

4. Calculating pressure
• Therefore the pressure on the surface of
mercury tube is equal to atmospheric pressure
• Thus atmospheric pressure (atm)is equal to
760mm or 76cm of mercury
• In the above process the vapor pressure of the
mercury above the mercury column is
neglected because it is very small

5. Monometer
A device for measuring pressure or comparing the
densities of two liquids.

6. U-Tube Monometer
• It consists of glass tube bent in u-shape.
• It’s one end is connected to a point whose
pressure is to be measured and other end
remains open to the atmosphere .
• The tube generally contains mercury or any
other liquid .

7. U-Tube Monometer
The equation for the pressure in the container is
:-

8. • The fact that the pressure at a certain level in a
liquid is the same at all points at that level is
used in the manometer

9. Pressure Altimeter
An instrument which is used to find the
pressure at different altitudes is called as
pressure altimeter or barometric altimeter.
Altimeter device to measure
the altitude or height.
As we know that greater the
altitude, the lower the pressure and vice
versa.

10. APPLICATIONS
• In taking of water to a higher level this
instrument can assist us a lot by measuring the
pressure at different level.
• A sea diver can also use it in order to know about
the depth.
• A pressure altimeter is the altimeter found mostly
in aircraft, and skydivers ,Hikers.
• It works on the principle that it measures height
to a certain reference point i.e sea level and then
pressure is measured accordingly.

11. Inclined leg manometer
• It is called inclined-leg manometer.
• uses >>
 It is use for
calculation
of small
pressure.
 principle:
• as we have to start
from one end and
proceed to the other
end.
Pa-Pb= r2h2+r3h3-r1h1 >> where “r” is specific weight of fluid
r3h3= r3Lsin(theta)
 As angle decreases, we can better measure small pressure upto higher accuracy.