Strain Gauge report

profileMike Otland
manual_rubric_appendex_3.zip

manual, rubric, appendex/.DS_Store

__MACOSX/manual, rubric, appendex/._.DS_Store

manual, rubric, appendex/Appendix.docx

A7

Appendix

List of Tables

Table 1 Calculated and measured values.

Readings

Deflection (in)

Output Voltage Vo (mV)

Strain

Force (lbs)

1

0.025

0.135

0.000152

1.03

2

0.125

0.76

0.000301

2.12

3

0.175

1.07

0.000972

5.18

4

0.225

1.38

0.001408

7.65

5

0.275

1.7

0.001652

8.72

6

0.325

2.01

0.002345

10.01

7

0.375

2.33

0.002916

11.44

8

0.425

2.65

0.003519

13.24

9

0.525

3.28

0.004021

16.04

10

0.625

3.91

0.005132

18.16

List of figures

Figure 1 Experimental setup of Flexor and NI ELVIS board

Figure 4 Lab view block diagram .

Figure 5 Voltage against deflection graph

Figure 6 Strain against deflection graph

Figure 7 Force against strain graph

List of Equations

1.

M = bending moment at gage centerline, in-lbs c = semi-thickness of beam, in I = moment of inertia of beam cross section, in4 P = load, lbs. L = effective beam length, in b = beam width, in t = beam thickness, in

2.

F=Force applied on beam

b =Thickness of beam

E= young’s modulus

=Strain

length of beam

3.

R= resistance

ΔR=change in resistance

L=length of beam

ΔL=change in length due to strain

4. Full bridge equation for strain and voltage relation.

Vr=voltage ratio

V=measured voltage

=Strain

GF=gage factor

References:

Voltage vs deflection

Output Voltage Vo (mV) 0.025 0.125 0.175 0.225 0.275 0.325 0.375 0.425 0.525 0.625 0.135 0.76 1.07 1.38 1.7 2.01 2.329999999999999 2.65 3.28 3.91

Deflection

Voltage Vo

Strain against Deflection

Strain 0.025 0.125 0.175 0.225 0.275 0.325 0.375 0.425 0.525 0.625 0.000152 0.000301 0.000972 0.001408 0.001652 0.002345 0.002916 0.003519 0.004021 0.005132

Deflection

Starin

Force against Strain

Force (lbs) 0.000152 0.000301 0.000972 0.001408 0.001652 0.002345 0.002916 0.003519 0.004021 0.005132 1.03 2.12 5.18 7.649999999999999 8.719999999999998 10.01 11.44 13.24 16.04 18.16

Strain

Force

__MACOSX/manual, rubric, appendex/._Appendix.docx

manual, rubric, appendex/Format.pdf

ME 3113 Measurements and Instrumentation Laboratory Fall 2015

Report Rubric

• Font

o 12 Point Times New Roman for main body of the report

o Section Headings should be 14 Point Times New Roman

• Formatting

o Report should be written entirely in third person passive

o 1.5 Line Spacing

o Justified Edges

o 1” Margins

o Do NOT indent the first line of each paragraph

o No bullet points in report

o The body of the report should be written in paragraph form using complete sentences.

o Figures, Tables, and Equations go in the appendix and are NOT to be imbedded in the body

of the report.

o Page Numbers go on the top right of the page with the following format, no page number on

the cover page, Abstract has page number i, Table of Contents has page number ii for the

first page and iii for the second page if applicable, Introduction through Conclusion are

numbered 1, 2, 3, 4……. , Appendix is numbered A1, A2, A3, A4……….

• Reports needs to have the following sections in the following order

o Cover Page

o Abstract

o Table of Contents

o Introduction

o Procedure

o Results and Discussion

o Conclusion

o Appendix

• Cover Page – Must contain the following Information

o Title of the Lab Experiment

o Written By: Your Full Name

o Lab Partner: Your Lab Partner’s Full Name

o Date Performed: January 19, 2015 Put the date you started the experiment

o Due Date: January 21, 2015 Put the date that the report is due on

o The University of Texas at San Antonio

o Mechanical Engineering Department

o ME 3113 Measurements and Instrumentation

o Fall 2015

o Section: Letter A through I depending on what lab section you are in

o Instructor: Dr. Victor Maldonado

o Lab Assistants: Jacob Byrd

Gregory Dannheim

Joshua Ward

o You may include a simple graphic on your cover page but it must be professional

• Abstract – Must contain the following information

o Purpose of the lab experiment

o What you did

o What you found

o What do your findings mean / why the reader should care

o General Engineering Significance (General application of the theory applied in the

experiment)

o ½ Page Max

- The Abstract should not contain any of the following

o Numerical Values

o References to Figures, Tables, Equations, or work cited

- The Abstract should be treated as a stand-alone document, which gives general statements on the

experiments purpose, procedure, outcome, and why the reader should care.

Table of Contents Abstract ----------------------------------------------------------------------------------------------- i

Introduction ------------------------------------------------------------------------------------------ 1

Procedure --------------------------------------------------------------------------------------------- 2

Results and Discussion ----------------------------------------------------------------------------- 4

Conclusion -------------------------------------------------------------------------------------------- 6

Appendix ------------------------------------------------------------------------------------------- A1

List of Tables

Table 1: Force Measurements ------------------------------------------------------------- A1

Table 2: Calculated Force Values --------------------------------------------------------- A1

Table 3: Error Analysis --------------------------------------------------------------------- A2

List of Figures

Figure 1: Force vs. Time Chart ------------------------------------------------------------ A2

Figure 2: LabVIEW Block Diagram ------------------------------------------------------ A3

Figure 3: Circuit Diagram ------------------------------------------------------------------ A4

List of Equations

Equation 1: Force ---------------------------------------------------------------------------- A4

Equation 2: Percent Error ------------------------------------------------------------------ A5

Equation 3: Uncertainty Analysis --------------------------------------------------------- A5

References -------------------------------------------------------------------------------------- A6

ii

Introduction The introduction should contain all background information necessary to complete the experiment.

Examples:

-If you used a caliper during the experiment, discuss the tolerance of the caliper, and possibly

reference a figure showing how the caliper was read.

-If you did analysis on a population of data, discuss the purpose of the analytical methods used and

any information necessary to perform the analysis.

-If you performed circuit analysis discuss KVL, KCL, Ohm’s Law, and any other pertinent theory

or laws.

- All software and hardware used in the experiment needs to be discussed with emphasis on the

most troublesome areas of the experiment.

If you feel the need to explain why you did something or what a word means when writing other

sections of the report, then you should include that information in the intro instead.

Introduction is max 1 page (If you are having trouble fitting all the pertinent information onto one

page, put the information that would be the most helpful to someone trying to complete the lab)

In the intro you can reference Figures, Equations, and cited sources.

Procedure Begins immediately after the Introduction (don’t start the Procedure on next page unless the

Introduction fills all of page 1)

The Procedure should be a step-by-step account of what you did to complete the entire lab

experiment. The Procedure has no limit on length and needs to be detailed enough to allow the reader

to complete the experiment and get the same results that you did. At the same time it shouldn’t be so

detailed that the reader doesn’t want to read it. For the reports in this class your procedure should

only need to be around 1½ pages. Do not rewrite the instructions in the lab manual. Write (in

paragraph form) what you did in your own words. Make sure to include any issues you came across

during the experiment with procedural steps on how you overcame these issues. Remember the entire

report should be written in third person passive. Write the Procedure as what was done not what

someone else should do. You should reference Figures (pictures you took of the experiment setup)

and Equations that are pertinent to the procedure of the experiment. For example if you are giving the

procedural steps on constructing a circuit, reference a Figure showing the circuit diagram or picture

of the physical circuit. If you reference something in the procedure in needs to be pertinent, not fluff

to expand the procedure. Do not reference Tables in the Procedure.

1

Results and Discussion The Results and Discussion (R&D) section of the report carries the highest weight out of all the

sections. In the R&D section you need to include:

• Representative Numerical Values from the theoretical and experimental data sets

• Need to reference every Table from the Appendix

• Error analysis with discussion on the cause of these errors

• Discussion of how the results (data points and analytical results) coincide with the expected

experiment outcome

• Discussion of the assertions made from your data and analysis

Conclusion The conclusion is the summary of the entire report and should include general statements on the

following:

• The purpose of the lab experiment

• Your data and analysis including error

• The outcome of the experiment

• A specific engineering significance (Specific application of the skills and techniques learned

in the experiment)

• Max 5 sentences

• There should be no numerical values or references in the conclusion

2

Appendix In the appendix you will have the following sections in the following order:

• Tables

• Figures

• Equations

• References

Each section should start on its own page with the section heading at the top of the page.

The entire appendix should be left aligned including the section headings.

Page Numbers should be on top right starting with A1

Tables - You need to have Tables for all data and values in the experiment

- Should be organized and preferably color coded

- Each Table should be labeled and titled Table 1: Title

- The Tables label and title should be above the Table and left aligned

- Should contain column/row titles including units

- Make sure you pay attention to your significant figures

- If Excel is used you need to have separate Tables showing the Excel code. These Tables

must also be referenced.

Figures - You need to have Figures for everything you did in the experiment (circuit diagrams,

pictures, charts, graphs, block diagrams………)

- Figure labels and titles go below the Figure and left aligned

- Also include Figures that assist in explaining the procedure

Equations - Include any Equations used in the experiment

- All your Equations should be formatted the same (Font, Size, Structure)

- Every equation needs to have its variables defined

- Every variable in an equation needs to be defined even if it was defined in a previous

equation

References - Any source used for the experiment or report needs to cited in MLA format labeled as

[1], [2], [3],…………… All references need to be cited in the body of your report.

The following page shows example pages on how you should format your appendix

! A1!

Appendix

Tables Table 1: Circuit 1 Voltage Values

! A2!

Figures

Figure 1: Circuit 1 Diagram

! A3!

Equations

Equation 1: Ohm’s Law

! A4! ! References

[1] Crane."Flow of Fluids, Through Valves Fittings and Pipe." Technical Paper No. 410

(2013): 2-24. Print.

[2] Kundu, Pijush K., and Ira M. Cohen."Internal Flow."Fluid Mechanics. 4th ed. Burlington:

Elsevier, 2007. Print.

  Referencing Tables, Figures, Equations, and Citations Every Table, Figure, Equation, and Citation needs to be referenced in the body of the report at least

once. Examples: The current measurements from circuit 1 can be found in Table 1.

The voltage across the 330 ohm resistor was measured as 2.54 volts (Table 2).

Circuit 2 was constructed in Multisim, as shown in Figure 2.

Following Ohm’s Law (Equation 2) the theoretical voltage was calculated.

For Citations: In the body of your report you need to cite all the sources you used. Do note use quotes in the body of

the report. Write the information in your own words. Example: Ohm’s law governs the relationship between voltage, current, and resistance [1].

[1] Represents the citation number on your references page.

Third Person Passive Means: Write about what was done not what you did or what someone else should do.

Do not use the following words: I, us, we, our, you, me, they, them………etc.

This is a general rubric for all lab reports used in M&I but additional formatting and components may

be necessary for individual lab reports.

__MACOSX/manual, rubric, appendex/._Format.pdf

manual, rubric, appendex/ME 3113 - Laboratory Exercise #6.docx

I. INTRODUCTION:

The purpose of this experiment is to construct a bending beam load cell. Bending strain will be measured to determine the vertical force applied to the beam.

II. EQUIPMENT:

1. Flexor, cantilever flexure frame

2. High-strength aluminum alloy beam

3. Micro-Measurements temperature-compensated strain gages (4)

4. Elvis II board & LabVIEW

III. PROCEDURE:

The gages have been pre-installed on the beam. The beam should be arranged so that the gages are located near the end of the beam which will be clamped in the Flexor (but clear of the clamp).

1. Back the calibrated loading screw out of the way, and insert the beam into the Flexor with the gaged end in the clamp and with the longitudinal gage on the upper surface.

2. Center the free end of the beam between the sides of the Flexor, and firmly clamp the beam in place with the knurled clamping screw. See Figure 1.

Figure 1. Flexor with beam

3. Use the DMM on the Elvis II to measure the resistance values of the strain gages on the beam.

4. Assemble your Wheatstone bridge on the Elvis II board with the 4 active arms of the bridge. Provide an excitation source of 5 Volts by connecting to the power terminals on the Elvis II board.

5. Use the DMM on the Elvis II to measure the output voltage Vo. Record this value. What should this value read?

6. Turn the loading screw to apply a downward force to the beam. If the Wheatstone bridge was configured properly, there should be a change in the output voltage of Wheatstone bridge as force is applied.

7. To display output voltage on LabVIEW, connect the jumper wires you used to measure output voltage to the analog inputs (ai0) on the Elvis II board (located on top left corner of the board). The analog inputs will read the output voltage changes of the strain gage as force is applied.

8. Create a LabVIEW program to read the voltage measurements by launching LabVIEW. In the block diagram, add a DAQ Assistant input (Input>DAQ Assist). Select Analog Input>Voltage>ai0.

9. After the DAQ assistant has been initialized change the max and min input range to 80mV and -80mV, or a range appropriate for your strain voltage readings. Verify that the scaled units are in volts, samples to read are 100, and rate is set to 1000 before pressing OK.

10. Add a signal filter (Signal Analysis>Filter) to help eliminate some of the noise that may occur from the initial strain measurements. Use trial and error to figure out what cutoff frequency and order is best for the filter.

11. Enclose your block diagram in a While loop.

12. Add a chart and numerical indicator to the block diagram to visualize the results. Change the tags from their default names to Voltage Chart and Voltage Indicator.

13. Press the run button and view the voltage when the beam is NOT deflected. If a voltage is displayed, add calculations to your block diagram to subtract the offset (calibration).

14. Apply force to the beam in small increments by turning the loading screw. Record the increment you choose. Collect at least 10 voltage measurements.

15. Construct a plot in Excel of strain and calculated force values.

16. Comment on your beam load cell, the bridge configuration, and the errors and uncertainties.

__MACOSX/manual, rubric, appendex/._ME 3113 - Laboratory Exercise #6.docx

manual, rubric, appendex/Strain gage measurements.docx

i

3

Abstract

The principle aim of this strain measurement lab was to study the parameters involved in the construction of a bending beam load cell. Experiment was conducted to determine the bending strain produced due to the force applied on the beam. A cantilever beam was clamped in the flexor and force applied on the beam was measured in the form of bending strain. Strain produced was converted into voltage by using wheat-stone bridge configuration. LabVIEW software was used to display the output voltage produced due to the applied vertical force on beam. NI ELVIS II board along with flexor and beam was used to obtain the relationship between strain values and resulting voltage change. From the experimental results and analyses of the data obtained it was observed that an increase in the applied force results in the increase in voltage.

Introduction

The determination of material strength is a very important parameter involved in the design and manufacturing of mechanical machines. One of the most prime parameter that is examined is the stress-strain property of the material used. Strain can be considered as an effect showing change or deformation of a material due to the applied force on its surface. When a beam is subjected to undergo a load applied then bending moment is produced. The bending moment can be described as the moment of inertia of the beam, stress, and deflection of the beam from its nominal axis. The mechanical equipment especially the bending beam load cells are manufactured keeping in mind its stress-strain parameters, then different tests are performed for checking the stability under conditions of force or load applied on the surface of loading cell. Usually strain is measured in very small amounts, a very small change in length of the beam is difficult to accurately measure when the change is several times smaller than the original length of the beam.Beams are classified into different categories a cantilever beam is one which has its one end clamped and the other one free. Normally a beam is examined to undergo the maximum stress and the results are used to obtain the material strength. It is also required to calculate the deflection on the beam under the maximum expected load. The solution to this problem is turning relating mechanical measurement to electrical measurement. A common tool used to measure strain is a strain gage. This gage is attached to the testing material at a location where strain measurement is desired, when force is applied on the test material then it changes its length depending on the force whether it expands or contracts. The strain gage measures this length change at that specific location on the test material. As the gage length changes, this change in length changes the electrical resistance of the wire of strain gage. For converting the change in resistance value of the wire into voltage a device is used known as wheat stone bridge. A full wave wheat stone bridge can be seen in figure 2 in appendix. As the force is applied on the test material then resistance of strain gage changes and this change is converted into voltage form which is easy to understand as compared to the resistance change. Output voltage produced can be calculated using the equation 4 of wheat stone bridge. NI ELVIS II board is used to interface the experimental results into LabVIEW software for presenting the graphical results and showing waveforms. LabVIEW program performs some manipulation techniques to refine the results and represent in more understandable format.

Procedure

NI ELVIS board, cantilever beam and flexor all were set up as following. Strain gages were attached to the one end of the beam. Both strain gages were installed on the uper surface of the beam and screw was backed out of the way and beam’s end with mounted strain gage was inserted in the flexor. The free end of the beam was centered between the sides of the flexor and tightly clamped with the clamping screw as shown in figure 3 in appendix. The wires from the strain gages were connected to the binding posts.. All the four wires of the Flexor cable were connected to the connector strip according to the connections shown in figure 3 in appendix. Resistances of the wires were measured by using the digital multi-meter in ELVIS board. All this set up was completed to perform the experiment and get results on the monitor. To display output voltage on LabVIEW window, the jumper wires were connected to the analogue inputs (ai0) on the ELVIS II board located on the top left corner of the board. Wheatstone bridge was connected on the ELVIS board with 4 active arms of the bridge as shown in diagram in appendix. Excitation voltage of 5V was connected to the power terminals of the board. The analogue inputs read the output voltage changes produced due to the applied force on the beam surface. LabVIEW software was launched and a DAQ assistant was added in the block diagram of simulation program. The input values for DAQ assistant were selected from Analogue input>Voltage>ai0.Then according to the requirements the minimum and maximum input ranges were adjusted between -80mV to 80mV and scales were adjusted to to read 100 samples and with the rate of 1000. A low pass filter (Signal Analyses>filter) was added in the block diagram so that unwanted noise to be removed from the output voltage waveform. For choosing the frequency cut off (fc) and suitable order of filter the trial and error method was used. A chart and numerical indicator was added to the window and names of the blocks were changed to voltage chart and voltage indicator. The RUN button was pressed when the beam was not subjected to applied force, initial voltage value was recorded when no deflection was observed. Then by turning the loading screw a force was applied in small increments, which produced certain amount of strain on the surface of the beam. On display of a voltage, calculations were added to the block diagram so as to subtract the offset calibration. Steps were repeated and values of load were increased slowly starting from lightly touched to a maximum value of 0.625 in. During the experiment there were some errors found, which were removed by simply turning the loading screw and choosing the specific data points All the output voltage Vo values for intervals starting from 0.025 to 0.625in were recorded in a table as shown in Table 2 in appendix. During the experiment the steps were repeated again and again to minimize the error or uncertainties produced. All the measurements were recorded carefully to avoid any mistakes. Relationship between strain and applied force was calculated using the equation 2 in appendix. Plots were drawn between different parameters using excel plots.

Results and discussion

Experimental setup was conducted as the steps mentioned in the procedure section and all the steps were performed according to the instructions. Measurements were recorded in the form of tables as shown in appendix. Strain gage provided the voltage values against the deflection on the beam, the results read from the strain gages were recorded an applied in calculations, in order to obtain the bending strain. Wires of the strain gage were connected to the ELVIS II board and DMM (digital multi meter) was used to measure the resistance. Resistance of Red-white was measured to be 0.09007 kΩ, Red-black was measured to be 0.12007 kΩ, Red green was 0.0914 kΩ. Once the bending strain was calculated the force to which the beam is subjected was calculated using the equation 2 from appendix, the young’s modulus of 29x10^6 and a gage factor of 2 was applied during calculations. Then voltage measurements were made for different deflection values on the beam. When there was no deflection applied to the surface of beam the output voltage was 0V as required condition of this experiment. Then a small amount of deflection was applied of 0.025in and output voltage reached 0.135mV. Again a small increment of deflection was applied and voltage was again increasing as expected and reached 0.76mV as shown in table 1 in appendix. Similarly same steps repeated many time and with maximum deflection of 0.625in the Vo value obtained was 3.91mV. This showed that there is direct relationship between deflection and output voltage Vo. Using these deflection and voltage values strain and force values were calculated using equation 2 and 4. With the strain value of 0.000152 the force applied was calculated to be 1.03lbs, similarly for maximum strain value of 0.005132 the force obtained was 18.16lbs. As the strain value increases the related force value also increased. In figure 4 the block diagram of LabVIEW program is shown which process the data obtained from experimental setup, low pas filter was added and cutoff frequency was adjusted for best output results without any noise factor, frequency was selected to 100hz and order of the filter was set to 3rd order. The output waveform was smoother and understandable as compared to unfiltered waveform. Figure 5 shows the deflection against voltage graph, it is clear from the graph that with increasing deflection the voltage is also increasing. Figure 6 shows the calculated strain values against that of deflection values, which is also in direct relationship with each other. In figure 7 the graph between strain and calculated force values is shown, as the strain values increases the force values also increases and reaches maximum value of 18.16 lbs.

Conclusion

For bending beam load cell construction this experiment was performed and relationship between applied force and output voltage was examined with the help of experimental results. The main objective of the experiment was achieved, by setting up a cantilever beam load cell and studying the behavior of the loading cell under certain conditions in the form of force applied. Using strain gages different strain readings were obtained and later applied in obtaining the vertical force. The relationship between strain and output voltage Vo was shown with the help of experimental data obtain during the experiment. A direct relationship was observed between strain and voltage Vo in the form of graphs plotted.