1. US Customary Measurement System
Introduction to Engineering Design
© 2012 Project Lead The Way, Inc.

2. The U S Customary System
Presentation Name
Course Name
Unit # – Lesson #.# – Lesson Name
The U S Customary System
System of measurement used in the United States
Similar to the British Imperial System of Measurement, but not identical
Common U S Customary Units
Measurement
Symbol
Unit
length in
inch ft
foot mi
mile
mass
slug
force lb
pound
time s
second
thermodynamic temperature F
Fahrenheit degree

3. Presentation Name
Course Name
Unit # – Lesson #.# – Lesson Name

4. Recording Measurements
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Course Name
Unit # – Lesson #.# – Lesson Name
Recording Measurements
A measurement always includes a value and unit of measurement
A measurement always includes error
No measurement is EXACT
A measurement is the best estimate of a quantity

5. Precision and Accuracy
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Unit # – Lesson #.# – Lesson Name
Precision and Accuracy
Precision (repeatability) = The degree to which repeated measurements show the same result
Accuracy = The degree of closeness of measurements of a quantity to the actual (or accepted) value
High Accuracy
Low Precision
Low Accuracy
High Precision
High Accuracy
High Precision
Low Accuracy
Low Precision

6. Recording Measurements
Presentation Name
Course Name
Unit # – Lesson #.# – Lesson Name
Recording Measurements
Ideally, a measurement device is both accurate and precise

7. Fractional Length Measurement
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Unit # – Lesson #.# – Lesson Name
Fractional Length Measurement
A typical ruler provides
A 12 inch scale (ruler) in US Customary units
Each inch is divided into smaller divisions, typically 1/16” increments

8. Recording Measurements
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Course Name
Unit # – Lesson #.# – Lesson Name
Recording Measurements
General Rules
Digital Instruments: Record all the numbers, including zeros after the decimal point, exactly as displayed
Decimal scaled Non-digital Instruments (mechanical): Record all digits that you can certainly determine from the scale markings and estimate one more digit
Fractional Scaled Instruments: estimate to half of the smallest increment
1/4” scale ruler you would estimate to 1/8 of an inch
1/2” scale ruler you would estimate to 1/4 of an inch
1/16” scale you estimate to 1/32 of an inch

9. The Inch
The divisions on the U S Customary units scale are easily identified by different sized markings. The largest markings on the scale identify the inch.

10. Presentation Name
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Unit # – Lesson #.# – Lesson Name
The Inch
Each subsequently shorter tick mark indicates half of the distance between next longer tick marks.
For example the next smaller tick mark indicates half of an inch = ½ inch
1/2

11. Presentation Name
Course Name
Unit # – Lesson #.# – Lesson Name
The Inch
Half of a half = ¼ inch. An English scale shows ¼ inch and ¾ inch marks.
All fractions must be reduced to lowest terms.
1/4
3/4
2/4

12. The Inch Half of a quarter = 1/8 inch 1/8 3/8 5/8 7/8 2/8 6/8 4/8
Presentation Name
Course Name
Unit # – Lesson #.# – Lesson Name
The Inch
Half of a quarter = 1/8 inch
1/8
3/8
5/8
7/8
2/8
6/8
4/8

13. The Inch Half of an eighth = 1/16 inch 1/16 5/16 9/16 13/16 3/16 7/16
Presentation Name
Course Name
Unit # – Lesson #.# – Lesson Name
The Inch
Half of an eighth = 1/16 inch
1/16
5/16
9/16
13/16
3/16
7/16
11/16
15/16
14/16
2/16
6/16
10/16
4/16
12/16
8/16

14. The Inch
Half of a sixteenth = 1/32 inch
3/32
1/32
5/32
2/32
4/32

15. Measurement: Using a Fractional Scale
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Unit # – Lesson #.# – Lesson Name
Measurement: Using a Fractional Scale
How long is the rectangle?
Let’s look a little closer

16. Measurement: Using a Fractional Scale
Presentation Name
Course Name
Unit # – Lesson #.# – Lesson Name
Measurement: Using a Fractional Scale
How long is the rectangle?
Inbetween in. and in. Closer to the middle than the tick marks
4/32(1/8)
6/32 (3/16)
What is the midpoint of 2 1/8 and 2 3/16?
5/32

17. Recording a Measurement: Using a Fractional Scale
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Unit # – Lesson #.# – Lesson Name
Recording a Measurement: Using a Fractional Scale
Do you think we are certain to the nearest ten thousandth? NO
We round 1/16” scale rulers to the nearest hundredth because we are only certain to the tenth and we take one more decimal place for an estimate.
2.16 in.

18. Recording a Measurement General Rule
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Course Name
Unit # – Lesson #.# – Lesson Name
Recording a Measurement General Rule
Record fraction measurements to the nearest 1/32 inch
Record decimal equivalent to the nearest hundredths of an inch on
We will always do this on 1/16th increment rulers. 2 5 32
in.

19. Record the measurement in fraction and decimal
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Course Name
Unit # – Lesson #.# – Lesson Name
Record the measurement in fraction and decimal
1. Record fraction
2. Convert fraction to decimal
Blue =
Red =

20. Stop
Complete problem 1 -5 in activity

21. What is the length of the blue and red rectangle
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Unit # – Lesson #.# – Lesson Name
What is the length of the blue and red rectangle 1. 2. 3.
Blue
Red
Green

22. Presentation Name
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Unit # – Lesson #.# – Lesson Name
What is the length of the blue, red, green and purple. All answers in fractions and decimals