precision measuring. precision – how close together or repeatable the results are –a precise...

Precision Measuring

Precision Measuring• Precision – How close together or repeatable

the results are– A precise measuring instrument will give nearly the

same result each time that it is used.

• Accuracy – How close a measurement is to the accepted value

– For example, a balance loaded with a standard 100g weight should read 100g. If it doesn’t, then the balance is inaccurate.

Precision measuring tools are needed for accuracy

Precision Measuring

• Precision = REPROCUCIBILITY

–Checked by repeated and repeated measurements.

• Accuracy = CORRECTNESS

–Checked by using a different form of measurement and obtaining the same value

Steel Rule

Micrometer

Tools for Precision Measuring

Digital Caliper

Dial Caliper

Tools for Precision Measuring

The dial caliper is a precision measuring instrument.

The caliper’s blade is broken into inchesand tenths of an inch (graduations).

Reading a Dial Caliper

inch

Each inch is broken into ten parts, each part is 1/10 or 0.1 of an inch

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The caliper’s dial graduations show thousandths (.001) of an inch.

The reference edge keeps track of larger increments; the dial shows us smaller increments.

Reading a Dial Caliper

One full revolution of the pointer on the dial equals one hundred thousandths (.100)(the same as 1/10 of an inch)

Blade

Inside Measuring Faces

Outside Measuring Faces

Dial

Fine Adjustment Screw

Dial Clamp Screw

Clamp Screw

Dial Caliper Parts

Step 1: Read inches from the blade

1 to 6 inches

2

Reading a Dial Caliper

Step 2: Read tenths of an inch from the blade

Reading a Dial Caliper

1 in. – 6 in.

0 to 9 tenths of an inch

2 3

Step 3: Read thousandths of an inch from the dial

Reading a Dial Caliper

0 to 9 tenths of an inch.001 to .099of an inch

2 3 2 8 1 in. – 6 in.

Dial Calipers Measure

• Thickness or Outside Diameter

Dial Calipers Measure

• Thickness or Outside Diameter

• Inside Diameter or Space Width

Dial Calipers Measure

• Thickness or Outside Diameter

• Inside Diameter or Space Width

• Depth

Dial Calipers Measure

• Thickness or Outside Diameter

• Inside Diameter or Space Width

• Depth

• Step Distance

Discussion Questions• List measurement tools…

Steel Rule Tape Measure

Dial Caliper Meter Stick

• Explain which one of the tools listed would be best to use and why when measuring: -The hallway

-Engineering Notebook

-Pencil diameter

-Height of your desk

Image Resources

Microsoft, Inc. (2008). Clip Art. Retrieved October 10, 2008, from http://office.microsoft.com/en-us/clipart/default.aspx

Wikimedia commons (2008). Retrieved October 15, 2008, from http://commons.wikimedia.org/wiki/ImageCaliper