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Chapter 5: Measure Pressure - Coggle Diagram
Chapter 5: Measure Pressure
Low pressure (Vaccum) measurement
Vacuum measurement are represent by unit Torr and micronOne Toor is a pressure equivalent of 1 mm of Hg while 1 micron
is 10¯³ Torr.
Manometer and elastic element gauges can be used to about
0.1 Torr.
Types of vacuum gauges:
McLeod Gauge.
Thermal Conductivity Gauge or Pirani Gauge
Ionisation Gauge.
Knudsen Gauge.
Pressure: Force per unit area, P=F/A
SI unit: Pa= N/m^2
Types of Pressure
Absolute Pressure: Fluid pressure above referrence value of a perfecr vaccum or the absolute zero pressure.
Gauge Pressure: Pressure above the reference value of atmospheric pressure.
Atmospheric pressure: at sea level is nearly 1.013x10⁵ N/m² or 760 mm of Hg. (Pressure in
the surrounding air)
Medium/moderate pressure measurement
Manometer:
Manometer is the simplest device for measuring static pressure.
Simple U-tube manometer uses water, mercury or any
suitable fluid.)
The different in level h between the two limbs is an indication
of the pressure different (p1-p2) between the two limbs.
h= (p1- p2) / pg
p: mass density of the liquid used in manometer
Bourdon Tube:
When pressure applied the elastic elements will get deformed.
Based on this deformation, the pressure can be measured.
Type of elastic element:
High pressure measurement
High-wire pressure tr
ansducer.
The technique based on the electrical resistance change of a
manganin (alloy of Cu, Ni, Mn) or gold chrome wire, with hydrostatic pressure to accommodate a bulk compression
effect.
Special techniques have to be used for measure the pressure
above 1000 atm.
The coil is enclosed in a flexible bellows, filled with kerosene
(medium of transmitting pressure to the coil).
Linear Variable Differential
Transducer (LVDT) pressure gauge
RANGE OF PRESSURE MEASURING DEVICE
