Pressure Measurements Presented By: Vinod Dahiya Lecturer Mechanical Engg. RGGP Narwana

Pressure Measurement

Pressure Pressure (P) expresses the magnitude of normal force(F) per unit area(A) applied on the surface. SI units :- Pascal (N/m²) Other units:- bar(=10⁵ pa),atm (=101.3kpa), mm hg or ( torr = 0.133322kpa)

Pressure measurement instrument Manometer U tube manometer Single column/micro manometer Well type manometer Inclined tube manometer Ring type manometer Pressure gauge Bourdon pressure gauge Bellow pressure gauge Bellow differential pressure gauge

U-tube manometers Just before connecting the U tube Just after connecting the U tube

U-tube manometer is a simple manometric device used to measure pressure at a point in a fluid. balancing the fluid column by the same or another column of fluid. in liquid column used manometric liquids are mercury, water or alcohol. Some of the important and desirable properties of the manometric liquids are: High chemical stability Low viscosity Low coefficient of thermal expansion Low volatility Low vapour pressure

Single Column/Micro-manometer Before connecting micro-manometer After connecting micro-manometer

Single column/micro-manometers are just similar to the U-tube manometer, only with a difference of having a small reservoir in the tube. Micro-manometer has a glass tube bent in “U” shape or inclined and has a small reservoir in the tube, having some amount of same or other type of fluid called manometric fluid.

Inclined tube manometer

An incline manometer is a manometer that uses an incline to measure a small pressure change. To calculate the pressure change for an incline tube manometer. γ = Specific Weight P = Pressure

Well type manometer Well type manometer

Ring manometer

Bourdon tube pressure gauge Principle:- The bourdon tube works on a simple principle that a bent tube will change its shape . As pressure is applied internally, the tube straightens and returns to its original form when the pressure is released . The tip of the tube moves with the internal pressure change and is easily converted with a pointer onto a scale.

Bourdon tube pressure gauge

Advantages:- Disadvantages:- Hysteresis on cycling Inexpensive Wide operating range Fast response Good sensitivity Direct pressure measurements Disadvantages:- Hysteresis on cycling Sensitive to temperature variations Limited life when subjected to shock and vibrations

Bellow pressure gauge Bellow pressure gauge

Bellow differential pressure gauge

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