Uncertainty calculation

Just let you know how to do uncertainty calculation. The entire machine in the earth is not 100% accurate. We need to reduce as less uncertainty as possible by two methods; arithmetic sum method or statistical approach method.

Linear Potentiometer

Introduction:                                                                                                              
The word linear can be referring to a straight line graph with voltage versus displacement. Consequently, the linear potentiometer is also called displacement transducers. The operation of this linear potentiometer is a voltage division on a hybride conductive film. However, there are a lot of types of linear potentiometer with different of products, design, specific range and displacement force. Here is the link http://www.waycon.biz/linearpotentiometers.html. This report is illustrated, measurement of output voltage after applying different displacement. The different displacements being apply the different voltage that can get.

Objective:

·         Performed adjusting the linear potentiometer displacement.
·         Performed measuring output voltage of linear potentiometer.
·         Recorded down the reading shown on multimeter of output voltage.

Criteria:
·         Correct process and work procedures while working on the linear potentiometer.
·         Make sure voltage supply equipment setting is correct set at 6V.
·         Make sure the reading is start from 0cm displacement of the linear potentiometer.

Tools and facilities or resources:
·         Linear potentiometer
·         Voltage supply equipment
·         Multimeter (at this experiment is using voltmeter)

Procedures:

1.      Prepared linear potentiometer, voltage supply equipment and multimeter (voltmeter) from George Jolley (lab assistant) or Dr. Geoffrey (academic lecturer) in engineering lab.

2.      Connected electrical wiring between linear potentiometer to the voltage supply equipment and the multimeter.

3.      Switched ON, the voltage supply equipment and the multimeter.

4.      Set the voltage supply equipment to 6V and turned the rotary switch of the multimeter to voltage and pointed the correct range of volt (V).

5.      Moved the pointer of linear potentiometer started at 0cm. The multimeter reading should be read at approximately 6V ± 0.2V. At here the reading has shown 5.8V.

6.      Move the pointer of linear potentiometer from 0 to 1cm and see the reading of the multimeter to measure the output voltage.

7.      Drop down and recorded every 1cm reading till 8cm of each voltage is shown.

8.      Repeated same experiment for twice to get more accurate reading by calculate average reading.

9.      After finish recorded, remember to switch off every equipment in engineering lab.

10.  Returned all the equipment to George Jolley.

 

Results:

Experiment to measure the output of a linear potentiometer

However there is no equipment is hundred percent accurate neither machinery nor human being.

Uncertainty:

·         Voltmeter Operating Uncertainty ± 2.00 percent.

Ø  The electronic circuits in the multimeter (voltmeter) produce to an uncertainty of ± 2.00 percent.

 

·         Voltmeter Resolution Uncertainty ± 0.005 Volts (0.08% at 6 volt point)

Ø  The voltmeter displays only two decimal places. This gives rise to a further uncertainty of ± 0.005 volts. At the result, this represents 0.08 percent of the displayed value if the instrument reads 6 volts.

Ø  The calculation is 0.005 x 100/6.0 = 0.083 ≈ 0.08%

Ø  0.005V due to < 0.005 ≈ 0.000 and > 0.005 ≈ 1.000

Ø  100 is 100 percent and it gives the percentage reading.

Ø  6.0 is 6V point of the setting in the voltage supply equipment.

 

·         Ruler Manufacturing Uncertainty ± 0.1mm (0.25% at 4cm point)

Ø  The ruler manufacturing process gives rise to an uncertainty of ± 0.1mm. As the result, at the 4cm (40mm) point this represents ± 0.25 percent.

Ø  The calculation is 0.1 x 100/40 = 0.25%

 

·         Ruler Resolution Uncertainty ± 0.25mm (0.63% at 4cm point)

Ø  Even if the ruler was totally accurate, the person using it would not read the indicated value with complete accuracy. The resolution uncertainty would vary depending on the eyesight of the user. Assume that this adds a further 0.25mm to the reading.

Ø  The calculation is 0.25 x 100/40 = 0.625 ≈ 0.63%

Consequently, the total measurement uncertainty of the output voltage can be calculated by simply adding all of the individual components. This experiment gives 4 cm point.

In fact, the experiment result shown at here is quite different by almost 3% compare to real life. It is because of several factors contributed to the measurement uncertainty to raise or lower down the value of the final result.

The other way to obtain uncertainty is using a statistical approach.  It is the best to repeat each measurement several times to determine more accurate reading by calculating average.

Calibration certificates stating for voltmeter and the ruler of probability distribution:

·         Normal distribution (divided by 2)

·         Rectangular distribution (1.732051)

·         Resolution has a rectangular distribution.

·         Repeatability is the exception to this rule because it has already gone through a statistical procedure.

Uncertainty Budget for 4cm point

To determine the expanded uncertainty budget, multiply the combined uncertainty by 2. To use the jargon, this gives the expanded uncertainty to a 95 percent confidence level. To certain that the output voltage, quote will be correct within ± 2.23 percent. (Calculated with longer decimal point that why not gets 2.22%) This is less than the uncertainty obtained using the Arithmetic Sum method.

 Analysis of the results:

1.      The results shown that statistical approach method (2.23%) have less uncertainty than arithmetic sum method (2.96%) that also means statistical approach method is more accurate.

2.      One of the reason statistical approach method more accurate is because it has been taken the value several times to avoid less calibration and eyes sight.

3.      The result of uncertainty is acceptable which not exceed 3% in real life.

4.      Uncertainly can be produced by calculation of decimal point, eyesight, length of wire (high resistance), wire of twisted (high resistance), and internal resistance of instrument equipment.

5.      The graph plotted should be straight line as name of “linear”.

6.      The longer distance of linear potentiometer, the smaller of the value of voltage output.

7.      The values of experiment 1, experiment 2, experiment 3 should be almost approximate the same ± 0.1 with average value.

8.      The average value is more accurate being plotted compare to experiment 1 graph.

 Comment/ Conclusion:

1.      The graph successfully being plotted.

2.      The entire instrument should be check for proper function before used.

3.      Refer to instruction or proper procedure or guide if not sure of using lab instrument.

4.      Take more experiment value to get more accurate reading.

 

Material Selection by using CES software

Introduction:

A vehicle jack is being select as a project to find out what kind of materials is suitable. It should able to withstand 500kg of load which is means it must has high yield strength or elastic limit. The price of the material should be cheap as well.

The material which is going to be consider for the vehicle jack:

·         Steel alloy: high yield strength, low cost
·         Composites: high tensile strength, low density
·         Other metal alloys: lower density

By checking from CES software the designer comes out of a solution to distinguish using other metal alloys as it is low yield strength or elastic limit and distinguish composites as well as the percentage composition material price is higher. Consequently, the materials which is going to compare is low carbon steel (AISI 1020), low alloy steel (AISI 4130 steel) and nodular graphite cast iron.

Theory

Generate Performance Index Formula
Material Weight (Mass)

Constraint: Yield strength

Objective: Mass

Constraint equation, σ = F/A              (1)

Objective equation, m (cylinder) = Cross section area, A x Length, L x Density, ρ (2)

Substitute this expression for A from equation (1) into equation (2), m = FL ρ / σ      (3)

The performance index, M₁ = σ /ρ

 

Material Cost

Constraint: Mass

Objective: Minimum material cost

For a component of mass, m kg, which costs £ C/kg, the material cost is m x C       (4)

Substitute this expression for m from equation (3) into equation (4), cost = FLρC/ σ

Hence to minimise material cost the performance index to be maximised is

M₂ = σ/ρC

A Materials Selection Chart can be made where elastic limit is displayed in function of the volume (figure1) and another displayed in function of the material cost per volume (figure 2). Figure 1 is useful to get a clear view on the material density that can be expected for certain material classes while figure 2 is useful to get a clear view on the material costs that can be expected for certain material classes.

Figure 1 show a graph Elastic Limit versus Density. The straight lines with slope = 1 (gradient) is constant. [The performance index, M₁ = σ /ρ; log M₁ = log σ – log ρ. Rearrange, log σ = log ρ + log M₁ = (y = mx + c). So, m = 1]. It is clear that low alloy steel will be low weight with the highest strength among all the materials selection.

Figure 2 show a graph Elastic Limit versus Density x Price. It is clear that nodular graphite cast iron will be expensive for this case. Carbon steel, AISI 1020 is beneficial from the viewpoint of cost but have low strength properties. This graph also shows that low alloy steel, AISI 4130 is more strength, low cost and very advantageous materials.

Figure 3 show a graph Elastic Limit/ Density which is represent performance index M₁. The best result regarding low weight (index M₁) is achieved with low alloy steel, AISI 4130 which is amongst other used in vehicle jack.

Figure 4 show a graph Elastic Limit/ Density/ Price which is represent performance index M₂. With respect to material cost (index M₂), low alloy steel, AISI 4130 give the best result and the selected carbon steel, AISI 1020 is situated closer to the defined lower limit.

Conclusion:

When all performance indices are taken into account, low alloy steel, AISI 4130 appear to be very attractive material for vehicle jack. This low alloy steel has elastic limit of 483-533.8MPa. For this material M₁ = 0.062-0.068 And M₂ = 0.151-0.248 (table).

 



Final Year degree project

This Project is design a vehicle jack use for electric kart in University of Sunderland, year 2012. The objective of the jacking device design should be safe, reliable and able to raise and lower the height level of vehicle, one person can be operated by applying forces to lifting handle, the price of the material should be cheap and it should be ergonomics to human body during working. By using CES software, material selection can be selected and lab experiment (HOUNSFIELD Test Specimens) to prove the test of maximum stress of the material without bend. According to the research, this vehicle jack can be used by worldwide female as the case study is being taken on the lowest female Asian height.

The outcome of vehicle jack will be view like

The lowest chassis height to ground should not exceed to 3 inches (76.2mm) as mentioned by Technical support; George Jolley. There is 20mm clearance left between the tyre to ground surface after the kart is being lift up. This 20mm should be able for technician to change the tyre without difficulty. This vehicle jack is also being prove can be used by worldwide female. As the designer has study about female height for using this jack (Disabled World, October 2008). (that blue box is jacking point)

 

The development of a new vehicle jack is also based on materials selection charts and performance indices. Two performance indices quantifying the performance of materials regarding weight and cost have been defined and evaluated. Low alloy steels are the materials with the best suited properties. When processing possibilities, recyclability and high corrosion resistance are taken into account, steel grades turn out to be very advantageous materials.

From the vehicle jack, a student can enlarge their knowledge such as physic theory application from internet and library resources, material selection to select best material based on performance indices and CES graphs, calibration and uncertainty of calculation from auto dynamic and control module, produce best quality vehicle jack from manufacturing design and able to manage the time and project from project management and control while automotive design give advice on using engineering software and product specification to qualify the best jack product.

February to JUne 2011

On Feb to June 2011, I have became Automotive Trainer at Times Academy while I am waiting for September 2011 to entry University of Sunderland, UK. 

 

Beside that, I also involved myself to be project planner, engineering researcher and home tutor.

 

One of the project I have helped student to plan is hydroelectric system. This project is just prototype and cant be applied in the real world.

 

Similar project has succeed and being apply:

 

 

Reused Greywater System (Higher National Diploma Final Project)

This project has awarded Distinction and I have put a lot of effort to study on electrical and electronic software and knowledge. I dont have electrical background but I willing to learn for improvement.

 





After assembly, again it has to be tested. This test is called first quality test to avoid error and achieve the objective of the project.

When no switch on power supply, there is no current pass through water level controller. The red and green L.E.D will not light up.

After switch on power supply, the red L.E.D will light up to show the voltage regulator is functioning. Then pour the water as shown in the above picture. The water will pass through filter and flow to aquarium pump arcyclic fiber tank.

The water level sensor will detect the water and send signal to water controller and at the same time light up green L.E.D. The water level controller will actuate the sensor to activate the water flowing from aquarium pump arcyclic fiber to another acryclic fiber (toilet).

Once again the toilet tank of water level sensor detect the water is maximum level, it send signal to water level controller to stop the pump from pumping water and at the same time green L.E.D will illuminate. Consequently, water will not flowing anymore from the pump.

The picture below shown that the project has completely success built in Kuching in the year 2003. This project is built for whole resident uses while my project is built for individual house usage.

Practice of Water Reuse and Recycle

Urban Reuse

The more common applications include irrigation of public access areas (residential lawns, parks, school yards, highway medians, golf courses, and landscaped areas surrounding hotels, offices, and commercial buildings). Other uses have included vehicle washing facilities, reflecting pools and fountains, fire protection, and toilet and urinal flushing. Urban reuse systems typically involve dual distribution systems that deliver reclaimed water to customers in a network of distribution piping separate from the potable distribution system. Examples of such systems are the Irvine Ranch Water District in California and the cities of St. Petersburg and Cape Coral in Florida. In St. Petersburg, Florida the dual distribution system has reduced potable water usage by 50%.

Agricultural Reuse

As Table 1 reflects, there are several different agricultural reuse categories. California and Florida have extensive programs accounting for between 34 and 63% of the total volume of reclaimed water used — depending on the source of the information. Prominent examples of agriculture reuse include the Cities of Orlando and Tallahassee in Florida. The system in Orlando is part of a joint program called Conserv II between the city of Orlando and Orange County, Florida.

Groundwater Recharge

Water Factory 21 in Orange County, California has been conducting reuse research and injecting effluent via wells into the coastal aquifer since 1976. WWTP effluent is combined with well water prior to injection. This indirect potable reuse has a psychological advantage in that there is a loss of identity between reclaimed water and groundwater. In Florida, the previously mentioned Conserv II program in Orlando also involves rapid infiltration basins for groundwater recharge.

Augmentation of Potable Supplies

Besides the indirect potable reuse just mentioned under the heading of groundwater recharge, direct potable reuse is also possible. There are major psychological barriers to this application although considerable research has been conducted in Denver, San Diego, and Tampa. Currently direct potable reuse is not practiced anywhere in the United States.

Environmental Enhancement

This category includes the use of reclaimed water for the creation or enhancement of wetlands, stream augmentation, and recreational and aesthetic impoundments. Examples of two major wetland enhancement systems to provide wildlife habitats as well as additional effluent treatment prior to discharge are sites at Orlando, Florida and Arcata, California. Other applications in this category include the creation of recreational lakes and snowmaking.

Industrial Reuse

In-plant recycling is an important part of many wet process industries. Separate from this, industrial applications of reuse (WWTP effluent) water include: evaporative cooling, boiler-feed water, process water, and irrigation of plant grounds (Goto, 1995). The cooling water application and the utility power industry are by far the predominant industry reuse situations.