‫جامعة الفراهيدي‬
‫هندسة تقنيات الطريان‬
‫خمترب ال‪Fluid Mechanics‬‬
‫‪Calibration of a bourdon pressure gage‬‬
‫عيل عامر عبد‬
‫املرحهل اثنية ‪group D‬‬
Experiment Calibration of a Bourdon Pressure Gage
Name of Experiment: Calibration of a bourdon pressure Gage
Aim of Experiment:
 To explain mechanism and operating Bourdon-tube pressure
gauge
 To determine the percentage of error for Bourdon –tube
pressure gauge by using a number of standard units of
pressure
 To calibrate a Bourdon type pressure gage
 To establish the calibration curve of Bourdon Gage.
Lead-in bourdon pressure gage:
A bourdon- tube gauge, measures the pressure by sensing the
deflection of a coil tube.
The pressure gauge is composed of a metal tube of copper with one
end closed and formed as 3/4 of a circle and the other end connected
to the pressure source.
The applied pressure causes a little expansion in the circular shape of
the tube, moving with it an attached pointer that is calibrated to
indicate the pressure.
When the applied pressure is more than the atmospheric pressure,
the end will diverge causing an expansion in the circular shape of the
tube.
There is a connected mechanism of levers and gears to amplify the
movement of the tube and transfer the action to a pointer that
indicates a definite pressure.
When the pressure gauge is disconnected, the pointer must indicate
zero pressure because in this case the pressure inside the tube is
equal to the outside pressure which is the atmospheric pressure.
The calibration of the pressure gauge is done according to this fact.
The accuracy of the pressure –gauge is dependent on its calibration.
The gauge must be calibrated from time to time especially after
applying, high pressure.
Calibration: it is defined as the process of comparison of specific values
of input and output of instrument with the corresponding reference
standards.
Instruments Used:
1.
2.
3.
Dead Weight Calibrator.
Set of Test weights
Bourdon pressure gage.
Theory of Experiment:
To calculate the percentage of error:
F =𝐦 ×𝐠
2
A= 𝝅 d ⁄4
S.P = F⁄A
P.E = |
𝑺.𝑷−AGP
S.P
|
To calculate the total percentage of error:
T.P.E. =
∑ P.E
N
× 100%
Where:
 P.E percentage of error
 S.P. starnded
 AGP average gague pressure
 T.P.E = Total percentage of error (%)
 N = Number of reading
Procedure:1-Remove the piston from the cylinder by using the hand.
2- Adjust the oil level in the open cylinder until the cylinder is
filled up to the edge.
3- The piston is re-inserted in to the cylinder of the pressure gauge
unit.
4- The mass is applied in five steps in each step 1 kg.
5- The gauge pressure reading is recorded. 6- The pressure is
reduced in five steps back to zero gauge.
7- Record the results in table
Reading:



Mass of piston = 1kg
Weight of piston = 9.81 N
Cross-sectional area = 333mm²
Case No.
1
2
3
4
5
Mass(KG)
1
2
3
4
5
Gage pressure increasing
5.92
8.85
11.82
14.79
17.77
Gage Decreasing
5.915
8.842
11.83
14.81
17.75
Cal:
S.P =
((1 + 1) ∗ 9.81)
⁄
= 5.891 bar
((333)10−2 )
A.G.P =
G.P(increasing)+G.P (decreasing)
2
S.P−A.G.P
P.E=|
|×
S.P
A.G. P1 =
5.92+5.915
2
= 5.9175
100%
5.891−5.9175
| 100%= 0.44%
5.891
P.E=|
T.P.E =
∑ P.E
N
× 100%
Result
Case
No.
Standard
pressure (bar)
Gage
Pressure
increasing
(bar)
Gage
Pressure
decreasing
(bar)
Average
Gage
pressure
(bar)
Percentage
of Error %
1
2
3
4
5
5.891
8.837
11.783
14.792
17.675
5.92
8.85
11.82
14.79
17.77
5.915
8.842
11.83
14.81
17.75
5.9175
8.846
11.825
14.8
17.76
0.44%
0.10%
0.35%
0.48%
0.50%
T.P.E = 1.85% / 5 = 0.37%
1-Plot
and
find
the
slope
for
:-
2-Define the Absolute, gauge and vacuum pressure?
Absolute pressure is a pressure that is relative to the zero pressure in the empty, airfree space of the universe. This reference pressure is the ideal or absolute vacuum
Gage pressure is the most often used method of measuring pneumatic pressure. It is
the relative pressure of the compressed air within a system. Gage pressure can be
either positive or negative, depending upon whether its level is above or below the
atmospheric pressure reference.
Vacuum is an air pressure measurement that is less than Earth's atmospheric pressure,
about 14.7 psi. A perfect vacuum, by definition, is a space where all matter has been
removed. This is an idealized description. Vacuum pressures that come close to the
“almost no matter” point are difficult and expensive to create.
3- List three materials used for bourdons tube, giving their pressure ranges
The Bourdon tube is an almost rectangular or elliptical cross-section tube made from
materials such as stainless steel or phosphor bronze.
4-What are the advantage and disadvantage of bourdon –tube gauge?
There are some advantages of bourdon tube are given
below,
o
o
o
o
o
o
Bourdon tube is simple in construction.
It is available in wide range.
It has long life.
It cost is low.
Time tested application.
Accuracy is high.
There are some disadvantages of bourdon tube are given
below,
o
o
o
Susceptibility to hysteresis.
Low spring gradient (below 50 psig)
Susceptibility to shock and vibrations.
5- Why the piston rotating until it’ s freely suspend ?
6- What are the sources of error in the experiment?