TABLE OF CONTENTS

Title .............................................................................................................Page

1. Experiment Title ..........................................................................................................2

1.1. Experiment objectives.................................................................................2

2. Introduction ..................................................................................................................2

3. Theoretical background ...............................................................................................2

4. Apparatus and procedure ..........................................................................................3-4

4.1. Apparatus....................................................................................................3

4.2. Procedure/s..................................................................................................3

5. Results...........................................................................................................................5

6. Discussion.....................................................................................................................5

7. Conclusion....................................................................................................................6

8. Recommendation..........................................................................................................6

9. References.....................................................................................................................7

1. EXPERIMEN T TITLE : PRESSURE MEASUREMENT AND CALIBRATION

1.1. Experiment objective:- Calibrate the pressure gauge using a “dead weight tester”.

2. INTRODUCTION :

In engineering, properties of materials such as pressure, density, ductility,

toughness, and hardness are important to be studied as these affect the

performance of many industrial applications .

To determine these properties, different types of apparatus are used. One of the

most commonly used apparatus to determine such properties (in this case the

pressure) is the pressure gauge. Many instruments have been invented to

measure pressure, with different advantages and disadvantages. Pressure range,

sensitivity, dynamic response and cost all vary by several orders of magnitude

from one instrument design to the next. The oldest type is the liquid column (a

vertical tube filled with mercury) manometer invented by Evangelista Torricelli in

1643. The U-Tube was invented by Christian Huygens in 1661. [1].

For a mechanical pressure gauge, accuracy is defined as a percentage of the

full-scale range [2]. To make sure that the apparatus (pressure gauge) is

accurate, a calibration method called dead weight tester (DWT) is used, using a

dead weight tester apparatus.

3 .THEORETICAL BACKGROUND:

Pascal’s principle – (definition of pressure):Pressure= ForceArea

Used to determine-calculate the actual pressure that is needed in the testing of

the pressure gauge.

4 .Apparatus and Procedure:

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4.1. Apparatus:

Deadweight tester (figure 1): apparatus uses known traceable weights to

apply pressure to a fluid for checking the accuracy of readings from a

pressure gauge [3].

4.2. PROCEDURE:

1- Bleeding the apparatus - using water as the fluid (figure 2) to apply pressure

(load) on it.

2- Placing weights (figure 3) on the table (figure 4) and reading off the pressure

for each weight (increasing pressure).

3- Removing the weights from the table and reading off the pressure readings

on the gauge again (decreasing pressure).

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)Figure 1 :(Deadweight tester apparatus- readings from a supplied pressure gauge

5 .RESULTS:

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)Figure 3 :(Different weight up to 5.2 kg. to be placed on the table above the piston.

)Figure 4 :(The piston which holds the weights on its surface

)Figure 2 :(The operating fluid. – Type: water

pressureDecreasingpressureIncreasingActual

Pressure

Total

mass on

piston

Mass added

to piston

Gauge

error%

Gauge

reading

(kN/m2)

Gauge

error%

Gauge

reading

(kN/m2)

(kN/m2)(kg)(kg)

3.69303.693031.1511

3.64455.784446.701.50.5

3.66603.666062.2820.5

4.94747.517277.852.50.5

9.01854.738993.4230.5

7.671153.66120124.5741

8.161434.95148155.7151

6.341756.34175186.8561

6. DISCUSSION:

As results shown, different types of weight were placed on the piston starting with

1 kg. of the piston weight itself, after this a 0.5 kg. and 1 kg. weights were added

gradually.

For the increasing pressure the error between the pressure gauge reading and

the actual pressure is start to be 3.69% for the first amount of weight, this shows

that there could be some friction, or due to lack of accuracy when reading the

gauge pressure, or it need more time to adjust itself as a first load on the piston.

The error decrease and increase with small amount, 5.78% for 1.5 kg. and 3.66%

for 2 kg, but after the third load were placed on the piston which equal 2.5 kg, the

error increased up to 7.51%, on this point an inaccurate reading for the pressure

gauge could be the main reason. After adding the next load the error decreased

and almost being stable at 3.66% comparing to the first load.

As the last weight added which equal 6 kg, the error increased again up to

6.34%, for this level a 6 kg weight could be considered as an over max weight for

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the apparatus, as the recommended max weight is 5.2 kg for the apparatus used

in the test.

For the decreasing pressure the error between the pressure gauge reading and

the actual pressure is said to be almost same to the increasing pressure, as

weight are removed gradually, the error should not reach a very high or very low

amount as it is a reverse action by removing the same loads which were added

respectively (same sequence).

It started with 6.34% and ended up with 3.69%, in between there were small

amounts of decreases and increases but for the load 2.5 kg the error was 4.94%

as it had a high error at the increasing pressure comparing to other errors during

the test.

7. CONCLUSION:

To conclude, using a dead weight tester method and its apparatus to calibrate

the pressure gauge would give an overall good result but there are many

effects that could change or decrease the accuracy of the gauge.

8. RECOMMENDATIONS:

- Using oil or air (gas) as an operation fluid, as they should give better or more

accurate results than water depending on the job site-manufacturer.

- Using a bigger or portable modified dimension for the deadweight tester to

increase the ability of taking or placing more loads (weights).

9. REFERENCES:

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[1]- “Pressure measurement,” http://en.wikipedia.org/wiki/Pressure_gauge

accessed October 7, 2013.

[2]- “Seven steps to select a pressure gauge,”

http://www.ashcroft.com/tech/upload/AshBulG_7.pdf accessed October 7,

2013.

[3]- “Deadweight tester,” http://en.wikipedia.org/wiki/Deadweight_tester

accessed October 7, 2013.

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