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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
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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
Tools for Precision Measuring Steel Rule Micrometer
Tools for Precision Measuring Digital Caliper Dial Caliper
Reading a Dial Caliper The dial caliper is a precision measuring instrument. The caliper’s blade is broken into inches and tenths of an inch (graduations). inch { Each inch is broken into ten parts, each part is 1/10 or 0.1 of an inch
Reading a Dial Caliper 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.
One full revolution of the pointer on the dial equals one hundred thousandths (.100) (the same as 1/10 of an inch)
Dial Caliper Parts Inside Measuring Faces Clamp Screw Dial Blade Fine Adjustment Screw Dial Clamp Screw Outside Measuring Faces
Reading a Dial Caliper 1 to 6 inches Step 1: Read inches from the blade 2
Reading a Dial Caliper Read tenths of an inch from the blade Step 2: 3 2 1 in. – 6 in. 0 to 9 tenths of an inch
Reading a Dial Caliper Step 3: Read thousandths of an inch from the dial 2 2 8 3 1 in. – 6 in. .001 to .099 of an inch 0 to 9 tenths of an inch
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 RuleTape Measure Dial CaliperMeter 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