1. Measurement of Pressure , Velocity, Acceleration Mass and Weight

2. STUDENT OUTCOME Able to understand the parameters
Measurements 17GN1001
STUDENT OUTCOME
Able to understand the parameters
Able to define and represent with units
Understand the conventional methods to measure.
Learn a specific instrument to measure.

3. Pressure
Pressure measurement is important because of the following reasons:
Pressure is an important quantity that describes a system.
Pressure is invariably an important process parameter.
Pressure difference is used many a time as a means of measuring the flow rate of a fluid.
Pressure level spans some 18 orders of magnitude from the lowest to the highest pressures encountered in practice

4. Measurement Of Pressure
Pressure is the amount of force applied perpendicular to the surface of an object per unit area.
Pressure is a scalar quantity.
The symbol for it is p or P.
P is the pressure
 F is the normal force,
A is the area of the surface on contact

5. Units and Conversion

6. Types of Pressure
Pressure may be measured with Reference to arbitrary Datum.
i) Absolute zero Pressure
ii) Local atmospheric pressure
iii) Gauge pressure or Vacuum pressure

7. Pressure Measurement Devices
Mercury manometer - U-shape, well-type
Uses the manometric fluid compression to indicate applied pressure
ii. Diaphragms - Flat, corrugated, SG based
Uses the deflection of member to indicated applied pressure.
iii. Bellows - Corrugated, LVDT coupled
Uses the compressive length change of convolution as in terms of applied pressure.
iv. Dead weight pressure tester - Balance type
Balanced pressure due to applied weight and buoyancy force are set equal to indicated pressure.
v. Bourdon pressure gauge - Pressure to displacement
Unknown pressure is converted into displacement and is indicated by a indicator.
vi. Mc Leod gauge - Low pressure compression
Uses the compression of low valued known pressure to indicate applied pressure.

8. Ranges of Pressure Low Pressure(Vaccume) Measurements:
Ex: Mcleod Gauge
Medium Range of Pressure
Ex: Manometers
High Pressure(Gauge)
Ex: C type Bourdon Tube

9. Dead Weight Pressure Tester
the dead weight tester is basically a pressure producing and pressure measuring device. It is used to calibrate pressure gauges

10. Manometers
Manometers can be used to measure gauge pressure, differential pressure and absolute pressure. Various types of Manometers 1.U tube Manometer 2.Well type or reservoir manometer 3.Inclined manometer 4.Float type manometer

11. Types of Manometers

12. U tube Manometer
The difference in pressure between the unknown pressure p and the atmospheric pressure p0 is determined as a function of the differential height h.
P – P0 = g . h (ρm – ρf )

13. Velocity Measurements
Velocity is a physical vector quantity; both magnitude and direction are needed to define it. The scalar absolute value (magnitude) of velocity is called "speed",
the SI (metric system) as metres per second (m/s) or as the SI base unit of (m⋅s−1).

14. Velocity Transducers
Velocity transducers are contact transducers, used to measure velocity.
They are usually mounted on bearing housing. Velocity transducers are still used in industry to some extent, mostly in condition monitoring such as industrial fans, pumps, etc.
The use of velocity transducers has shifted to accelerometers that are internally “integrated” to velocity. Velocity transducers are suitable for mid-range frequency measurement.

15. Velocity Transducer
A velocity transducer/sensor consists of a moving coil suspended in the magnetic field of a permanent magnet.
The velocity is given as the input, which causes the movement of the coil in the magnetic field. This causes an emf to be generated in the coil.
This induced emf will be proportional to the input velocity and thus, is a measure of the velocity.

16. Animation

17. Acceleration:
Acceleration is a vector quantity that is defined as the rate at which an object changes its velocity. Units: m/sec2…. ms-2.
An object is accelerating if it is changing its velocity.

18. Types of acceleration Increasing speed Decreasing speed
Example: Car speeds up at green light
Decreasing speed
Example: Car slows down at stop light
Changing Direction
Example: Car takes turn.
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19. Accelerometers are mainly used for two specific types of acceleration measurements- impact (shock) and vibration.
Impact is effectively a large acceleration over a short period of time, while vibration is a small. repeatable acceleration.
Accelerometers are also used to measure the position, velocity or acceleration of bodies, such as aircraft and ships.
Accelerometers are normally mechanically bonded to the object whose acceleration is to be measured.
The accelerometer detects acceleration along one axis and is insensitive in orthogonal directions.

20. Accelerometers

21. Principle of Operation
When the object accelerates, the
mass displaces relative to the
object. causing a deformation
in the crystal.
this deformation in the piezoelectric crystal causes in turn a electric charge between its conductive coatings as a result of the piezoelectric effect. this electric charge is proportional to the mechanical deformation

22. Mass & Weight
Mass is a measure of the amount of material in an object. The unit of mass, the kilogram
Weight is the gravitational force acting on a body

23. Mass & Weight
The international prototype of the kilogram is kept at BIPM, the International Bureau of Weights and Measures in Sèvres, Paris.
It consists of an alloy of 90% platinum and 10% iridium in the form of a cylinder, 39 mm high and 39 mm in diameter. It is stored at atmospheric pressure in a specially designed triple bell-jar.

24. Loadcell
A load cell is a “load transducer” which converts the weight or load acting on it into electrical signals.
A load cell is composed of an aluminum alloy spring element, strain gauges (serving as sensors) and a bridge circuit.
The strain gauges themselves are bonded onto four areas which become considerably distorted in the spring element. The load cell detects the force of the distortion as voltage change.