Pressure measuring instruments

It is useful all type of students, Professionals, Teachers and Industry persons. It includes various types of pressure gauge like Pressure Measurement, Absolute pressure, Vacuum Pressure, Gauge pressure, Diaphragm pressure GaugeBellows pressure gauge, Simple Manometer, Differential Manometer, Inclined Leg Manometer, U tube Manometer, Bourdon Pressure, Dead Weight.

1. PROF. S D YADAV
MGM’S JNEC AURANGABAD
MAHARASHTRA ,INDIA.
PRESSURE MEASURING
INSTRUMENTS

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2. Different Types of Pressure
1.Absolute pressure: is defined as the pressure which is measured with reference
to absolute vacuum pressure.

2. Gauge pressure: is defined as the pressure which is measured with the help of a
pressure measuring instrument, in which the atmospheric pressure is taken as
datum. The atmospheric pressure on the scale is marked as zero.

3.Vacuum pressure: is defined as the pressure below the atmospheric pressure.
Note. (i) The atmospheric pressure at sea level at 15°C is 101.3 kN/m
2 or 10.13 N/cm
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3. 1 Manometers.
Manometers are defined as the devices used for measuring the pressure
at a point in a fluid by balancing the column of fluid by the same or
another column of the fluid.
(a) Simple Manometers, (b) Differential Manometers.

2. Mechanical Gauges.
Mechanical gauges are defined as the devices used for measuring, the
pressure by balancing the fluid column by the spring or dead weight.

The commonly used mechanical pressure gauges are :
PRESSURE Measuring Devices
(a) Diaphragm pressure gauge,
(c) Dead-weight pressure gauge, and
(b) Bourdon tube pressure gauge,
(d) Bellows pressure gauge.
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4. CLASSIFICATION OF PRESSURE
MEASUREMENT DEVICES
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5. SIMPLE MANOMETERS
A simple manometer consists of a glass tube
having one of its ends connected to a point
where pressure is to be measured and other
end remains open to atmosphere.

Common types of simple manometers are :
1.Piezometer.
2.U-tube Manometer.
3.Single Column Manometer.
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6. PIEZOMETER
Pressure at A =⍴gh N/m²
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7. U-tube Manometer

It contains two liquids
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8. Let A be the point whose pressure is to be measured.

h₁ = Height of light liquid above the datum line.
h₂ = Height of heavy liquid above the datum line.
⍴₁ = Density of light liquid.
⍴₂ = Density of heavy liquid.

Pressure above A-A in the left column=P+ ⍴₁ *g* h1
Pressure above A-A in the left column= ⍴2 *g* h2

Hence equating the two pressures
P + ⍴₁ *g* h₁ = ⍴₂ *g* h₂

P=(⍴₂ *g* h₂ - ⍴₁ *g* h₁ )
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9. SINGLE COLUMN MANOMETER
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10. SINGLE COLUMN MANOMETER
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11. Vertical single column Manometer
•It is a modified form of U-tube manometer.
•It contains reservoir.
•Change in liquid level is very small in the
reservoir.

Inclined single column Manometer
•It is more sensitive
•Distance moved by the heavy liquid in the
right limb will be more.
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12. PROF. S D YADAV
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13. U TUBE DIFFERENTIAL MANOMETER
Inverted U Tube Differential Manometer
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14. RANGES OF BOURDON TUBE
PRESSURE GAUGES
•C- type bourdon tube elements 0-700 mega Pascal & even
higher.
•Spiral type bourdon tube elements 0-30 mega Pascal.
•Helical type bourdon tube elements 1.5 mega Pascal to 550
mega Pascal.

15. C-TYPE BOURDON TUBE
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16. HELICAL TYPE BOURDON
TUBE
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17. SPIRAL TYPE BOURDON TUBE
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18. BELLOWS PRESSURE GAUGE
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19. BELLOWS PRESSURE GAUGE
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20. bellows are also used for pressure measurement, and can be made of
cascaded capsules. The basic way of manufacturing bellows is by
fastening together many individual diaphragms. The bellows element,
basically, is a one piece expansible, collapsible and axially flexible
member. It has many convolutions or fold. It can be manufactured form a
single piece of thin metal. For industrial purposes, the commonly used
bellow elements are:
By turning from a solid stock of metal
By soldering or welding stamped annular rings
Rolling a tube
By hydraulically forming a drawn tubing

Working

The action of bending and tension operates the elastic members. For
proper working, the tension should be least. The design ideas given for a
diaphragm is applied to bowels as well. The manufacturer describes the
bellows with two characters – maximum stroke and maximum allowable
pressure. The force obtained can be increased by increasing the
diameter. The stroke length can be increased by increasing the folds or
convolutions.
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21. DEAD WEIGHT PRESSURE GAUGE
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22. DIAPHRAGM PRESSURE GAUGE
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23. A diaphragm pressure transducer is used for
low pressure measurement. They are
commercially available in two types – metallic
and non-metallic.
Metallic diaphragms are known to have good
spring characteristics and non-metallic types
have no elastic characteristics. Thus, non-
metallic types are used rarely, and are usually
opposed by a calibrated coil spring or any
other elastic type gauge. The non-metallic
types are also called slack diaphragm.
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24. Thank You
PROF. S D YADAV
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