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How to Present ExperimentalData in Graphical Form

Engineering 111

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Whats wrong with this picture?

2080

2100

2120

21402160

2180

2200

2220

2240

2260

-4 1 6 11

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Basics requirements

2080

2100

2120

2140

2160

2180

2200

2220

2240

2260

-4 -2 0 2 4 6 8 10 12 14

StaicandTotalabsolutepressure

s(lb/ft^2)

Probe position (inches)

Pressure Profile Through Ramjet

Static Pressure

Total Pressure

Title

Legend

x-axis label (abscissa)

the independent variable

y-axis label (ordinate) the dependent variable(s)

Units

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Basics requirements

2080

2100

2120

2140

2160

2180

2200

2220

2240

2260

-4 -2 0 2 4 6 8 10 12 14

StaicandTotalabsolutepressure

s(lb/ft^2)

Probe position (inches)

Pressure Profile Through Ramjet

Static Pressure

Total Pressure

Unique data symbols

Axis scaleReasonable axis minimum (origin not always at 0,0)

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Axis scales

Must use easily interpretable scales

i.e. units of 1, 2, 5, 10, 25, 50, 100, etc.

Not units of 7, 16, 67, etc.

Axis min/max must be such that the data

curve fills the entire graph

If some data isnt scaled with other data,

make it scaled

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What is wrong?

0.0

10.0

20.0

30.0

40.0

50.0

60.0

0.00

0.37

0.74

1.10

1.47

1.84

2.21

2.58

2.94

3.31

3.68

4.05

0 328 656 984 1312 1640 1968 2296 2624 2952 3280 3608 3936

Efficiency

TorqueandBHP

Speed (RPN)

Impulse Turbine Performance Curves

Torque (ft-lbf)

BHP (HP)

Efficiency (%)

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What is wrong?

0.0

10.0

20.0

30.0

40.0

50.0

60.0

0.00

0.37

0.74

1.10

1.47

1.84

2.21

2.58

2.94

3.31

3.68

4.05

0 328 656 984 1312 1640 1968 2296 2624 2952 3280 3608 3936

Efficiency

TorqueandBHP

Speed (RPN)

Impulse Turbine Performance Curves

Torque (ft-lbf)

BHP (HP)

Efficiency (%)

Range extends beyond dataHard to interpolate scale

Data is poorly scaled,

cant see whats going

on

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Much Better

0.0

10.0

20.0

30.0

40.0

50.0

60.0

0.00

0.50

1.00

1.50

2.00

2.50

3.00

3.50

4.00

0 500 1000 1500 2000 2500

Efficiency

TorqueandBHPx10

Speed (RPN)

Impulse Turbine Performance Curves

Torque (ft-lbf)

BHP (HP)

Efficiency (%)

Note the secondary y-

axis; this aids in

visualizing data with very

different ranges

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Trend lines and best fit curves

Theoretical data does not need data points as

you are plotting a curve from equation

Experimental points must be plotted and then

connected with a best fit line or trend line

You DO NOT connect experimental data points

with lines as you do not know exactly what

happened between recorded data points

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Theoretical and experimental pressure

heads in a venturi

0

50

100

150

200

250

300

1 2 3 4 5 6 7 8 9 10 11

PressureHead(mm)

Position

Pressure Head and Velocity versus position

Recorded Pressure Head

Calulated Pressure Head

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Whats wrong?

0

50

100

150

200

250

300

1 2 3 4 5 6 7 8 9 10 11

PressureHead(mm)

Position

Pressure Head and Velocity versus position

Recorded Pressure Head

Calulated Pressure Head

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Whats wrong?

0

50

100

150

200

250

300

1 2 3 4 5 6 7 8 9 10 11

PressureHead(mm)

Position

Pressure Head and Velocity versus position

Recorded Pressure Head

Calulated Pressure Head

Are you telling me the

slope of the data is

exactly this?

And then abruptlychanges to this?

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Consider the following equation

I want to find the average value of k

for a set of data.

Well, conveniently, the above

equation is in the form:

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The recorded Data:

Location Radius (mm)

Temperature

(Celcius) r/r1

r1 12.7 136.4 1.00

r2 19.1 110.0 1.50

r3 25.4 91.5 2.00

r4 31.8 80.5 2.50

r5 38.1 68.6 3.00

r6 44.5 59.6 3.50

r7 50.8 51.4 4.00r8 57.2 43.4 4.50

r9 63.5 36.1 5.00

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Finding the slope, B

0

20

40

60

80

100

120

140

160

0.00 1.00 2.00 3.00 4.00 5.00 6.00

Temperature(Celcius)

r/r1 Note the logarithmic data trend,

how do I find the slope of the

data to use in my equation?

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Method 1

0

20

40

60

80

100

120

140

160

1.00 10.00

Temperature(Celcius)

r/r1

Change x-axis to log scale

Slope is now calculated as:

Best fit line through the data that

we want to find the slope of

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Method 2Slope is now calculated as:

0

20

40

60

80

100

120

140

160

0.000 0.100 0.200 0.300 0.400 0.500 0.600 0.700 0.800

Temperature(Celcius)

Log10(r/r1)

Axis remains normal scale but we have used

Log10(r/r1) as the independent variable this time

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Assignment

Graph the following data on one graph. The flow rate is theindependent variable.

You may need to use multiple ordinates or you can scalesome of the data.

Be sure to make it clear in the axis labeling if you scaled thedata

This is due in hardcopy format on the last day of class,Monday, Feb 7.

This assignment is to be done on a computer, NOT by hand

If you cannot get the program to give a nice best fit linethrough your data points, you can do that by hand once youhave printed it all out.

Color or black and white is fine.

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Flow Rate

(ft^3/sec)

Heat (ft) Brake Horsepower

(HP)

Efficiency (%)

0.00 116.52 0.0379 0.0

0.00 107.64 0.0360 0.0

0.42 98.76 0.0329 17.1

0.66 94.32 0.0316 26.8

0.89 85.45 0.0310 33.3

1.07 82.12 0.0278 42.8

1.22 79.90 0.0316 41.9

1.65 71.02 0.0306 51.9

1.85 63.25 0.0291 54.6

2.16 53.26 0.0272 57.4

2.34 39.95 0.0237 53.4

2.47 29.96 0.0224 44.6

2.69 21.08 0.0221 34.7

2.77 7.77 0.0215 13.6

2.77 2.22 0.0209 4.0

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