CAPE COAST TECHNICAL UNIVERSITY
SCHOOL OF ENGINEERING
DEPARTMENT OF MECHANICAL ENGINEERING
MECHANICAL ENGINEERING LAB
COURSE CODE : BME 201
DEAD WEIGHT CALIBRATION EXPERIMENT
LAB REPORT 1
OPTION: BTECH PLANT
NAME: SAKYI JUNIOR ASUAKO
INDEX: 0103101121
DATE TO BE SUBMITTED : 10 FEBUARY, 2023
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TABLE OF CONTENT
PAGE NUMBER
ABSTRACT…………………………………………………………………………………………………………………….. 3
INTRODUCTION………………………………………………………………………………………………………..…….3
OBJECTIVE………………………………………………………………………………………………………………………3
APPARATUS…………………………………………………………………………………………………………………….4
THEORY……………………………………………………………………………………………………………………..……7
METHOD/PROCEDURE………………………………………………………………………………………….………..8
TABULATION, CALCULATIONS AND GRAPH…………………………………………………………………….8
DISCUSSION……………………………………………………………………………………………………….………….12
SOURCE OF ERROR…………………………………………………………………………………………………………12
ENGINEERING APPLICATION………………………………………………………………………………….………12
CONCLUSION………………………………………………………………………………………………………………..12
RECOMMENDATION………………………………………………………………………………………………….…12
REFERENCES………………………………………………………………………………………………………………..13
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ABSTRACT
On the basis of Pascal’s Law, in this experiment we calibrate a pressure gauge using the “Dead Weight
Calibrator”. A change in pressure at any point in an enclosed fluid at rest is transmitted undiminished to
all points in the fluid. A dead weight calibrator is simply a device that controls the pressure of a fluid by
changing the weight of its body. A dead weight calibrator just controls the weight of its body.
INTRODUCTION
One of the main procedures used to keep instruments accurate is instrument calibration. Instrument
calibration is very vital in engineering fields, it ensures safety, reduces cost from manufacturing errors
due to calibration errors on instrument, hence the importance of instrument calibration. It involves
setting up a tool to produce findings that fall within a reasonable range. Weights that are recognized are
applied to a Dead Weight Calibrator to pressurize a fluid and test the accuracy of pressure gauge
readings.
The intensity of the pressure at any location in a static or moving fluid has been measured using a
variety of pressure measurement instruments. The Bourdon tube pressure gauge is one of these
gadgets. Nowadays, Bourdon-tube pressure gauges are the most popular due to their dependability,
compactness, low price, and simplicity of use. It is made of a curved tube with an elliptical cross section
that has been bent into a circular arc .
When pressure is applied to the tube, it tends to straighten out, and the deflection of the end of the
tube is communicated through a system of levers to a recording pointer. This gauge is widely used for
steam and compressed gases. The pressure indicated is the difference between the system pressure and
to the external (ambient) pressure, and is usually referred to as the gauge pressure
AIMS OR OBJECTIVES
The objective of this experiment is to ;
 Produce a calibration of a bourdon gauge
 Determine the accuracy in a bourdon gauge reading and calibration equipment
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APPARATUS





Hydraulic bench
Piston
Bourdon gauge
Dead weight
Hydraulic Cylinder
Hydraulic Bench : is a self-contained water supply device that allows recirculating
water from a Sump Tank into different hydraulic devices. A centrifugal Pump moves water
from the Sump Tank through a hose into a Water Inlet at the top of the bench. It is applied in
flow meter calibration, fluid friction apparatus, jet trajectory and orifice flow .
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BOURDON GAUGE: is a mechanical device used to measure and display pressure. The
gauge can be used for measuring pressure in both gas and liquid state systems.
PISTON: A piston is a component of reciprocating engines, reciprocating pumps, gas
compressors, hydraulic cylinders and pneumatic cylinders, among other similar mechanisms. It is
the moving component that is contained by a cylinder and is made gas-tight by piston ring
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DEAD WEIGHT
CYLINDER : A hydraulic cylinder is a tube that produces linear actuation utilizing hydraulic pressure.
Basically, the pressure of a hydraulic fluid forces a piston to move in either a pushing or pulling motion.
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A DEAD WEGHT CALIBRATION SET-UP
THEORY
Dead Weight Calibrator unit works on Pascal’s Law or the principle of transmission of fluid-pressure
which states that pressure exerted anywhere in a confined incompressible fluid is transmitted equally in
all directions throughout the fluid.
P=
𝐹𝑜𝑟𝑐𝑒
𝐴𝑟𝑒𝑎
But Force = Mass × Acceleration Due To Gravity
Therefore P =
𝑀𝑎𝑠𝑠 × 𝐺𝑟𝑎𝑣𝑖𝑡𝑦
𝐴𝑟𝑒𝑎
Pressure is an important parameter in engineering. There are several methods for pressure
measurement where it employs hydrostatic principles .Bourdon gauge pressure is one of the several
methods. The mechanism of the gauge can be seen through the transparent dial of the instrument . A
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tube with a thin wall of oval cross-section is bent into a circular arc. It is firmly covered at one end where
pressure(fluid) is admitted to the tube and is free to move at the other sealed end. When pressure is
admitted, the tube tends to straighten. The experiment is solely based on pressure and the principle of
hydrostatics.
METHOD OR PROCEDURE
During the process it is necessary to clear air bubbles by gently taping the system.
 Organize the apparatus for the experiment; bourdon gauge, cylinder, piston, dead weights and
hydraulic bench .
 Set up and adjust the ball eye or spirit level to center.
 Remove the piston from the unit.
 With outlet valve sealed, gently pour a continuous steady flow of water(fluid) into the cylinder
to over flow onto the bench.
 Completely fill the tube with fluid till the system is void of air or bubbles.
 Gently place the piston into the cylinder and allow to settle.
 Record the initial gauge pressure reading corresponding to the mass of the piston.
 Carefully add weight onto the piston and record the gauge pressure reading corresponding to
the mass.
 Repeat the process for number of successive weights and record their pressure readings against
their masses .
 During the process, to prevent the piston from sticking , rotate the piston gently as each mass is
added.
TABLES, CALCULATIONS AND GRAPHS
TABLE
Mass Of
Piston
Mp
( Kg )
Diameter Area Of
Of
Piston A
Piston d ( m² )
(m)
0.498
0.01766
0.498
0.498
Mass Of
Weight
Mw
( Kg )
Total
Mass M
Gauge
Reading
G
Calculated
Pressure
P
( KN/m² )
Absolute
Gauge
Error
(KN/m²)
Percentage
Gauge
Error
(%)
0.000245 0
0.498
20
19.940
0.06
0.3009
0.01766
0.000245 0.5
0.998
40
39.960
0.04
0.1001
0.01766
0.000245 1.0
1.498
60
59.981
0.019
0.0317
8
0.498
0.01766
0.000245 1.5
1.998
75
80.001
-5.001
-6.2512
0.498
0.01766
0.000245 2.0
2.498
120
100.021
19.979
19.9748
0.498
0.01766
0.000245 2.5
2.998
135
120.042
14.958
12.4606
0.498
0.01766
0.000245 3.0
3.498
160
140.062
19.938
14.2351
CALCULATIONS
Area Of Piston
Area =
𝜋𝑑²
4
Where d =diameter of piston
D= 0.01766 m
Therefore Area =
𝜋( 0.01766 )²
4
= 0.000245 m²
Total Mass
Total mass =Mass of piston (Mp) + Mass of weight (Mw)
Mp= 0.498 Kg
When Mw =0, 0.498 + 0 = 0.498 Kg
Mw =0.5, 0.498 + 0.5 = 0.998 Kg
Mw =1.0, 0.498 + 1.0 = 1.498 Kg
Mw =1.5, 0.498 + 1.5 = 1.998 Kg
Mw =2.0, 0.498 + 2.0 = 2.498 Kg
Mw =2.5, 0.498 + 2.5 = 2.998 Kg
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Mw =3.0, 0.498 + 3.0 = 3.498 Kg
Calculated Pressure
Pressure ( P ) =
𝐹𝑜𝑟𝑐𝑒
𝐴𝑟𝑒𝑎
But Force = Mass × Acceleration Due to Gravity
Therefore P =
When M =0.498,
𝑀𝑔
𝐴
0.498 ×9.81
0.000245
= 19.940 KN/m²
M =0.998,
0.998 ×9.81
=
0.000245
M =1.498,
1.498 ×9.81
0.000245
M =1.998,
1.998 ×9.81
=
0.000245
M =2.498,
2.498 ×9.81
0.000245
M =2.998,
2.998 ×9.81
=
0.000245
M =3.498,
3.498 ×9.81
0.000245
39.960 KN/m²
= 59.981 KN/m²
80.001 KN/m²
= 100.021 KN/m²
120.042 KN/m²
= 140.062 KN/m²
ABSOLUTE GAUGE ERROR
AG= G – P
20 – 19.940 = 0.06 KN / m²
40 – 39.960 = 0.04 KN / m²
60 – 59.981 = 0.019 KN / m²
75 – 80.001 = -5.001 KN / m²
120 – 100.021 = 19.979 KN / m²
135 – 120.042 = 14.958 KN / m²
160 – 140.062 = 19.938 KN /m²
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GAUGE ERROR PERCENTAGE
G.E% =
𝐺𝑎𝑢𝑔𝑒 𝑅𝑒𝑎𝑑𝑖𝑛𝑔−𝐶𝑎𝑙𝑐𝑢𝑙𝑎𝑡𝑒𝑑 𝑃𝑟𝑒𝑠𝑠𝑢𝑟𝑒
𝐶𝑎𝑙𝑐𝑢𝑙𝑎𝑡𝑒𝑑 𝑃𝑟𝑒𝑠𝑠𝑢𝑟𝑒
Therefore ;
20−19.940
19.940
× 100 %
× 100 % = 0.3009 %
40−39.960
×
39.960
100 % = 0.1001 %
60−59.981
59.981
× 100 % = 0.0317 %
75−80.001
80.001
× 100 % = -6.2512 %
120−100.021
100.021
× 100 % = 19.9748 %
135−120.042
×
120.042
100 % =12.4606 %
160−140.062
×
140.062
100 % = 14.2351 %
GRAPH
A GRAPH OF ABSOLUTE GAUGE ERROR AGAINST GAUGE
READING
ABSOLUTE GAUGE ERROR
25
20
15
10
5
0
0
20
40
60
80
100
120
140
160
180
-5
-10
GAUGE READING
DISCUSSION
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During the experiment, be mindful of air bubbles forming in the fluid to affect the pressure readings or
eventual system failure. This can be achieved by tapping the system to eliminate the air bubbles.
SOURCE OF ERROR
Errors in this experiment may arise from ;




Air bubbles inside the tester unit resulting in inaccurate reading.
Static friction between the piston and cylinder yielding smaller gauge reading .
Wear and backlash in the gauge linkage or valves affecting the pressure readings.
Human error.
ENGINEERING APPLICATIONS




The bourdon tube is used in analog pressure meter.
It is used in many hydraulic systems.
It is used in foot pump to in indicate pressure developed.
They are used to measure pressures ranging from medium to very high, for highpressure applications, such as steam boilers and compressors.
 Used for measuring pressure in vehicles' tube tires.
CONCLUSION
In this experiment our objective was to produce a calibration of a bourdon gauge. In view of our
objective, the results obtained shows the calibration curve of the system. The curve represents
the relation between the masses and gauge pressure readings.
RECOMMENDATION
In general the whole experiment was quite a success.
 The outlet valve should be firmly covered when filling the system with fluid to avoid air
from entering the system.
 Gently tap the system to get rid of air bubbles to avoid inaccurate pressure readings.
 Ensure a continuous steady flow of fluid into the cylinder.
 The laboratory is conducive for fluid experiments.
 The laboratory lacks water flow which makes carrying out experiments very tedious, this
should be attended to urgently.
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REFERENCES
Bao, M., Sun, Y., Yang, H., Wang, J., 2003, “A fast and
accurate calibration method for high sensitivity pressure
transducers”. Sensors and actuators A: Physical, Vol. 108, No.
1-3, pp. 218–223.
Kojima, M.; Saitou, K.; Kobata, T., 2007, “Study on
Calibration Procedure for Differential Pressure Transducers”.
IMEKO 20th TC3, 3rd TC16 and 1st TC22 International
Conference Cultivating metrological knowledge, Merida,
Mexico.
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