PPT based on the instruments used for measuring pressure temperature etc

1. “INSTRUMENTS AND MEASUREMENT”
Presented By
Yogesh Kumar Chouhan
ID- 220116010
Presentation
On
Swami Vivekanand College of Agril.Engg. And Tech. & Research
Station, IGKV Raipur
2017-18
(PFE-512)
Farm Structure
and
Environmental Control
Submitted To
Er. P. Pisalkar

2. CONTENT
Pressure Measurement
Types of Pressure Transducers
Temperature Measurement
Temperature Measurement Instruments
Flow measurement

3. PRESSURE MEASUREMENT
 It is represented as a force per unit area
 Pressure SI unit: Newton per square meter(N/m2) or pascal
(Pa)
 Term used:
 Absolute pressure: refers to the absolute value of the
force per unit area exerted on the containing wall by the
fluid.
 Gauge pressure: represent the difference between the
absolute pressure and the local atmospheric pressure.
 Vacuum pressure: represents the amount by which the
atmospheric exceeds the absolute pressure.

4. TYPES OF PRESSURE TRANSDUCERS
There are many types of pressure transducers:
1) Mechanical Pressure-Measurement Devices (Manometer)
a) U-tube Manometer
b) Well-type Manometer
2) Bourdon-Tube Pressure Gauge
3) Diaphragm
4) Bellows Gauges

5. MANOMETER:
 A manometer is a device for measuring fluid
pressure consisting of a bent tube containing one or
more liquids of different densities.
 A known pressure (which may be atmospheric) is
applied to one end of the manometer tube and the
unknown pressure (to be determined) is applied to
the other end.
 Differential pressure manometer measures only the
difference between the two pressures.

6. U-TUBE MANOMETER
 The U tube contains two different liquids. The yellow
liquid on the right has a higher density than the blue
liquid on the left and so less of it is needed to give the
same pressure at points A and B. The pressure at the
points A and B must still be the same.
 The pressure at A is due to the ordinary air pressure plus
the height of the column above A and the pressure at B
is the higher air pressure plus the liquid column above B.

7.  If the pressure on one limb of a U tube is
greater than the other this difference in
pressure can be measured by simply
finding the difference in height (h) of the
liquid in the two limbs of the U tube

8. WELL-TYPE MANOMETER

9. BOURDEN TUBE
 Bourdon gauge is used to sense the pressure change across
an orifice and is calibrated to the gas flow rate.
 The bourdon-tube itself is usually an elliptical cross-sectional
tube having “C” shape configuration.
 Used in many applications because of its consistency,
 and inexpensive measurement of static pressure
measurement.

11. DIAPHRAGM:
 It represent similar types of elastic deformation devices
useful for pressure measurement applications.
 The diaphragm will be deflected in accordance with this
pressure differential and the deflection sensed an appropriate
displacement transducer.

13. BELLOWS GAUGE
 A differential gauge pressure force causes displacement
of the bellows, which may be converted to an electrical
signal or undergo a mechanical amplification to permit
display of the output on an indicator dial.
 The bellows gauge is generally unsuitable for transient
measurements because of the larger relative motion and
mass involved.
 The diaphragm gauge which may be quite stiff, involves
rather small displacements and is suit for high frequency
pressure measurement.

15. TEMPERATURE MEASUREMENT
 Controlling temperature is one of the most common processes
in industrial electronics and manufacturing.
 Manufacturing processes that are affected by temperature are
referred to as thermal systems.
There are 4 scales that can be used to measure temperature.
 Celsius/Fahrenheit units are used in the common everyday
scales
 Kelvin/Rankine are used when working with the Absolute
Temperature Scale ( these are typically used in engineering
and research calculations)

16. LIQUID IN GLASS THERMOMETER
The liquid in a glass thermometer, either colored alcohol or
mercury, expands as it heats and condenses as it cools. In
a thermometer, the liquid cannot expand outward and the
only place it can go is up or down. Temperature on a glass
thermometer can be measured in Fahrenheit, Celsius or
Kelvin

17. ADVANTAGES
 Easy portability
 Independence of auxiliary equipment
 Low cost
 Compatibility with most environments
 Moderate ruggedness
 Wide range (it has been use to measure
temperatures as low as 70K and as high as
1000°C, but it most frequent use is within -40°C to
250 °C)

18. DISADVANTAGES
 A large sensing element
 Impossibility for continuous automatic readout,
 Long time constant
 Awkward dimensions, and hysteresis (except for
special types),
 breakage(mercury contamination)

19. BIMETALLIC THERMOMETER
The bimetallic strip can be wound as a helix and will twist
when heated. This twisting action can be used to drive a
pointer over a calibrated temperature scale. These
temperature sensors are low cost and have accuracy
ranges of between 2-5% and are mostly used for local
readings. They are not suitable for providing a continuous
output measurement

20. GAS FILLED THERMOMETERS
 Closed system, contains a gas or a volatile liquid and
relies on pressure measurements to provide temperature
indications.
 When temperature changes , fluid either expands or
contracts, which caused Bourdon tube to move, thereby
moving the position of the needle on the scale

22. THERMOCOUPLES (TCS)
 A thermocouple consists of two pieces of dissimilar
metals with their ends joined together (by twisting,
soldering or welding)
 A thermocouple is an electrical device consisting of two
dissimilar conductors forming electrical junctions at
differing temperatures. A thermocouple produces a
temperature-dependent voltage as a result of
the thermoelectric effect, and this voltage can be
interpreted to measure temperature.
 Based on Seebeck Effect which simply states that an
electromotive force (emf) is created at the junction of 2
dissimilar metals when heated.

24. FLOW MEASUREMENT
 Flow measurement is the quantification of bulk fluid
movement.
 Accurate measurement of flow rate of liquids and gases
is an essential requirement for maintaining the quality of
industrial processes. In fact, most of the industrial control
loops control the flow rates of incoming liquids or gases
in order to achieve the control objective. As a result,
accurate measurement of flow rate is very important.

25. ROTAMETER
 Cone shaped tubes that contain a bobbin(Bob).
 The gas enters the bottom of the tube applying a force to
the bobbin.
 The bobbin then moves up the tube until the force
pushing it up is cancelled out by the gravitational force.
 At this point it remains at that level and there is a constant
pressure across the bobbin.

27.  At low flows, the bobbin is near the bottom of the tube and
the gap between the bobbin and wall of the flowmeter acts
like a tube (diameter < length)
 Gas flow is laminar and hence the viscosity of the gas is
important
 As flow rate increases, the bobbin rises up the flowmeter
and the gap increases until it eventually acts like an orifice
(diameter > length)
 At this point the density of the gas affects its flow

28. THANK YOU