1. PRESSURE MEASUREMENT PART - I Er. FARUK BIN POYEN Dept. of AEIE, UIT, BU, BURDWAN, WB, INDIA faruk.poyen@gmail.com

2. Contents: 1.Unit of Pressure 1.High Pressure 2.Low Pressure 2.Different Types of Pressure 1.Gauge Pressure 2.Absolute Pressure 3.Vacuum or Differential Pressure 4.Static Pressure or Velocity Pressure 3.Methods of Pressure Measurement 4.Manometers 1.U – tube Manometer 2.Well type Manometer 3.Barometer 4.Inclined Manometer 5.Micro manometer 6.Ring Balance Manometer 10/5/2016PRESSURE MEASUREMENT - PART I Er. FARUK BIN POYEN2

3. Pressure: Defined as the amount of force applied to a surface or distributed over it and is measured as force per unit area. Units of Pressure (P = F/A) The basic unit of pressure in SI units is the Pascal (Pa). It is defined as force of 1 Newton (N) per square meter (m 2 ). That is: 1 Pa = 1 N/m 2. High pressure 1 N/m 2 = 1 Pa; 1 atm = 14.696 psi = 101.325 kPa Low pressure 1 millibar = 100 dyne/cm2 = 14.5 * 10 -3 psi 1 micron = 10-6 Hg = 19.34 * 10 -6 psi 1 torr = 1 mm Hg = 19.34 * 10 -3 psi 10/5/2016PRESSURE MEASUREMENT - PART I Er. FARUK BIN POYEN3

4. Different Types of Pressure Absolute Pressure = Gauge Pressure + Atmospheric Pressure 10/5/2016PRESSURE MEASUREMENT - PART I Er. FARUK BIN POYEN4 Fig 1: Different Pressure Scales

5. Vacuum or Differential Pressure: Gauges that indicate gauge pressure may be designed to indicate pressures below zero. Such a gauge is called a “vacuum gauge”. Hauges that indicate absolute pressure cannot indicate pressures below zero as zero is a perfect vacuum. Static Pressure and velocity Pressure: When the fluid is in equilibrium, the pressure at a particular point is identical in all directions and independent of the orientation. This is called static pressure. Velocity pressure is the difference between the total pressure and static pressure. Velocity Pressure = Total pressure – Static pressure 10/5/2016PRESSURE MEASUREMENT - PART I Er. FARUK BIN POYEN5

6. TABLE I: Relationship between Units 10/5/2016PRESSURE MEASUREMENT - PART I Er. FARUK BIN POYEN6

7. Methods of Pressure Measurement 1.Manometer Method 2.Elastic Pressure Transducer 3.Measuring Vacuum Method 4.Force Balancing Method 5.Electrical Pressure Transducer 10/5/2016PRESSURE MEASUREMENT - PART I Er. FARUK BIN POYEN7

8. Manometers: Range: 0.2 MPa or 2 kg/cm 2 U – tube Manometer: Well – type Manometer: 10/5/2016PRESSURE MEASUREMENT - PART I Er. FARUK BIN POYEN8 Fig 2: U – tube Manometer Fig 3: Well – type Mano meter

9. Barometer: Inclined Manometer: Micro manometer: 10/5/2016PRESSURE MEASUREMENT - PART I Er. FARUK BIN POYEN9 Fig 4: Barometer Fig 5: Inclined Manometer Fig 6: Micro Manometer

10. Ring-Balance Manometer: 10/5/2016PRESSURE MEASUREMENT - PART I Er. FARUK BIN POYEN10 Fig 7: Ring Balance Manometer Fig 8: manometers in different shapes

11. Errors in Manometer: Effects of Temperature Capillary Effect Effect of Variable Meniscus Fluids for Manometer: Water Red oil Mercury 10/5/2016PRESSURE MEASUREMENT - PART I Er. FARUK BIN POYEN11

12. Advantages of Manometer: Simple and time proven High accuracy and sensitivity Wide range Reasonable cost Suitable for low pressure and low differential pressure Disadvantages of Manometer: Large and bulky Levelling is required Compatibility required between manometer fluid and measured fluid No over – range protection Condensation is a potential problem 10/5/2016PRESSURE MEASUREMENT - PART I Er. FARUK BIN POYEN12

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