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MEC 322: CHAPTER 5 ( CONTROL SYSTEM AND INSTRUMENTATION ) - Coggle Diagram
MEC 322
: CHAPTER 5
( CONTROL SYSTEM AND INSTRUMENTATION )
INTRODUCTION
Pressure means force per unit area (P = F/A), exerted by a fluid on the surface
of the container
SI unit : Pascal (Pa) = N/m²
Method of
pressure measurement
VERY HIGH
High-wire pressure transducer
measure the pressure
above 1000 atm
The technique based on the electrical resistance change of a
manganin (alloy of Cu, Ni, Mn) or gold chrome wire, with hydrostatic pressure
FORMULA
For a wire of diameter D and length L, the resistance
p being resistivity constant,
Starains (Ex, Ey, Ez) in the perpendicular direction in terms of stresses
substituting
MODERATE
2 TYPES
MANOMETER
h = (p1-p2) /pg
Measuring Static Pressure
CHARACTERISTIC
a. non-corrosive and not have any chemical reaction with the
fluid which pressure is being measured.
b. low viscosity to ensure quick respond to pressure changes.
c. should have negligible surface tension and capillary effects.
OTHERS
.Cistern or well type manometer.
h = (p1-p2) /pg
.Inclined tube manometer
.
p1-p2 = pgl [ (A2/A1) + sin θ]
.Micrometer type manometer.
.Movable tube type micromanometer.
.Micromanometer with motor drive and digital read-out.
VERY LOW
represent by unit :
:check: 1 Torr = 1 mm of Hg
:check: 1 micron =10¯³ Torr
Manometer and elastic element gauges can be used to about
0.1 Torr. Below that range, vacuum gauges are needed
MC LOAD GAUGE
Thermal Conductivity gauge
P= (1/K) (L1/L2 )
Ionisation Gauge
Formula
LVDT = High Presure gauge
100 to 10^8 Pa
