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Pressure measuring devices
- 1. MINI PROJECT GROUP MEMBERS: •Aqeel Ur Rehman • Naseem khan • Aqib Ahmad • Asmat Ullah • Ubaid Ullah
- 2. TOPICS • Pressure measuringdevices • Piston gauge • Manometers • Bourdon pressure gauge • McLeod gauge
- 3. PRESSURE MEASURING DEVICES •Instruments used to measure pressure are called pressure gauges or vacuum gauges • The oldest type is the liquid column (a vertical tube filled with mercury) manometer invented by Evangelista Torricelli in 1643. • The U-Tube was invented by Christian Huygens in 1661.
- 4. McLeod Gauge Principle : Aknown volume gas is compressed to a smaller volume whose final value provides an indication of the applied pressure • A McLeod gauge isolates a sample of gas and compresses it • McLeod gauge reading is dependent on the composition of the gas Useful range: • Useful range is from 10−4Torr (roughly 10−2 Pa) to vacuums as high as 10−6 Torr • McLeod gauge can measure lower pressure directly
- 5. McLeod Gauge COMPONENTS AND WORKING: Appliedpressure P1 Mercury level is raised by piston Mercury level reaches zero reference point Here we find pressure
- 6. MEASUREMENT OF PRESSURE •P1 = ah2/(V1-ah) Where, h = height of the compressed gas in the measuring capillary tube P1 = Applied pressure of the gas unknown. P2 = Pressure of gas at final condition= P1+h • Since ah is very small when compared to V1, it can be neglected. Therefore, P1 = ah2/V1 APPLICATION The McLeod Gauge is used to measure vacuum pressure
- 7. BOURDON PRESSURE GAUGE •Bourdon patented his gauge in France in 1849 • Cheap, reliable and accurate • Principle: flattened tube tends to straighten or regain its circular form in cross section when pressurized
- 8. COMPONENTS OF BOURDONGAUGE • Glass plate • Face plate • Screws • Housing/casing • Pivot and pivot pin • Link • Sector gear • Pinion • Needle
- 9. WORKING • Increased pressure…………..Flattened tube tends to straightened and needle rotates clockwise • Decreased pressure……….... Tube tends to contract and needle rotates counter clockwise APPLICATIONS • Cars • Industries
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- 11. PISTON GAUGE • Piston-typegauges counterbalance the pressure of a fluid with a spring (for example tire-pressure gauges of comparatively low accuracy) or a solid weight
- 12. DEADWEIGHT TESTER • Pressure measuringdevice and also used for calibration • Principle: pressure of the fluid is counter balanced by the weights and friction drag COMPONENTS AND WORKING:
- 13. CALCULATING PRESSURE • PA= Mg + F Hence : P = (Mg + F ) / A where, P = pressure M = Mass; Kg g = Acceleration due to gravity ; m/s² F = Friction drag; N A = Equivalent area of piston – cylinder combination; m² Thus the pressure P which is caused due to the weights placed on the platform is calculated.
- 14. APPLICATIONS • It isused to calibrate all kinds of pressure gauges such as industrial pressure gauges, engine indicators and piezoelectric transducers
- 15. MANOMETERS DIFFERENTIAL MANOMETER: It isused to measure pressure difference between two pipelines or containers. Components: 1) U shaped tube 2) Liquid (mercury or water) Working Calculation
- 16. • PA+ ρAg*(x+h)= PB+ ρBg*y+ ρmg*h • PA-PB = (ρBg*h+ ρmg*h)- ρAg*(x+h) • In this way we can find pressure difference
- 17. MANOMETERS CONTD INCLINED MANOMETER: It isslant manometer It is used to measure very small pressure difference Components : Working: Calculation:
- 18. Pa+ ρ a*g*(Rm+x)= Pb+ ρb*Rm*g+ ρa*g*x
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- 20. Aneroid Gauges • Aneroidmeans “without fluids” and the term originally distinguished these gauges can be used to measure the pressure of a liquid as well as gas. • Aneroid gauges are based on a metallic pressure-sensing element that flexes elastically under the effect of a pressure difference across the element. • Aneroid gauges are often called mechanical gauges in modern languages. • These are not dependent on the type o gas being measured , unlike thermal and ionization gauges.
- 21. • Ionization gaugesfor measuring low pressure only . • Thermal gauges are used by the phenomenon that DENSITY INCREASES PRESSURE INCREASES HEAT PRODUCED HEAT MEASURED BY WIRE FILAMENT
- 22. Bellow Pressure Gauge WORKING: •Bellows are tubular membranes which are present inside the bellow pressure gauge. • Here the pressure to be measured is applied outside the bellows. • It contains an elastic element that is spring. • Here the movements of the bellows can be converted into linear displacement. • The displacement can be converted in terms of pressure.
- 23. • Used tomeasure the flow pressure of a peaceful river etc. Application • It is adaptable for absolute and differential pressures
- 24. Spinning Rotor Gauge •The spinning rotor gauges works by measuring the amount of a rotating ball is slowed by the viscosity of the gas being measured. • Here the ball is made of steel and is magnetically levitated inside the steel tube closed at one end and exposed to the gas to be measured at the other. • The range of this instrument is 0.000001 Pa to 100 Pa. • It is accurate and stable enough to be used as a secondary standard. • Also this instrument requires some special skills and knowledge to use it correctly.
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- 27. Application of spinninggauge • High vacuum gauge calibration and metrology. • Gas kinetics measurements. • Thermal and chemical research
- 28. Magnetic coupling • Thesegauges use the attraction of two magnets to translate differential pressure into motion of a dial pointer. • As differential pressure increases , a magnet attached to either a piston or rubber diaphragm moves . • A rotary magnet that is attached to a pointer then moves in union ,to create different pressure ranges, the spring rate can be increased or decreased.