Measurement Chapter 8

Why Measure? Measurement is the practice of comparing the qualities of an object to a standard. To describe objects using measurement, we have created systems of standards of comparison.

Early Measurements Early Egyptians, Romans, and Greeks used the human body to start an early system of measurement. Foot – originally based on the size of a human foot. Cubit – Length of an Arm from the elbow to the tip of the middle finger (page 158). Palm – Width of 4 Fingers Digit – Width of a Single Finger.

Current Measurement Systems Today, each major physical quality is compared to a standard measurement that has been set by government standards. The two measurement standards in use in the world are: U.S. Customary or English (feet, inches) International System of Units (Metric)

U.S. (English) System The U.S. customary system of measurement is based on the system that developed in England from approximately the 1100s to the 1500s. The system is confusing because of inconsistencies in computing fractions and multiples of different base measurements. For example, one inch is 1/12 of a foot, where as one quart is ¼ of a gallon.

U.S. (English) Measurement Some elements of ancient systems still remain in the words we use. Size: Inch – means thumb in some languages. There are 12 inches in a foot Mile – 5,280 feet. Comes from the length of one thousand paces of a Roman legion. Volume: Quart – 4 quarts in a gallon Pint – 2 Pints in a quart

The Metric System In the 1790s a group of French scientists assembled to create a measurement system that was more logical and exact. The metric system is also simpler because it uses a prefix to show us how the base unit is being changed. For example the unit for distance is the meter. The metric system uses the same prefixes for all base units. The metric system is considered to be a more precise measurement system and is primarily used in medicine and other industry where precise measurement is needed.

Metric System Measurements Everything is based on 10. Size: 10 millimeters in a centimeter 10 centimeters in a decimeter 10 decimeters in a meter Volume: 1,000 milliliters in a liter. Weight: 1,000 grams in a kilogram.

The second is the same for time measurement in both systems. U.S. Customary Metric Inch Centimeter Mile Kilometer Degrees Fahrenheit Degrees Celsius Pound Kilogram Gallon Liter The second is the same for time measurement in both systems.

More About Measurement Several distance measurements may be used when describing a part or product. The U.S. customary system IS NOT built on the decimal system. Precise measurements ARE NOT usually needed when building a home. Machinist’s rules are designed for finer measurements than bench rules. A sliding T-bevel DOES NOT allow for a direct reading when measuring an angle. The measurement tools an operator manipulates and reads ARE NOT called indirect-reading measurement tools. Mass is the amount of matter present in a material. The gravitational pull exerted on an object is weight.

What can we measure? Size and Space Mass Temperature Time Volume Speed Distance Dimension

Size and Space When we measure the size and shape of an object, we may encounter three different but related measurements: length or distance, area, and volume.

Measuring Length or Distance Length is the separation between two points. Length and distance are generally given in a single measurement from Point A to Point B. A Many parts or products are described as having thickness, width, and height B Length: A & B Thickness Width

Measuring Area Determining the area of something involves measuring both length and width and then multiplying the two to determine how much surface the object covers. L x W = Area Length Width

Measuring Volume The amount of space that an object occupies or encloses Volume is calculated by multiplying the length, width, and depth of an object. L x W x D = Volume The measurement is expressed in cubic units. Width Depth Length

Types of Measurements Standard Measurement: Measurement that is close but not exact. Length of a piece of wood. Building a House Floor Covering Precision Measurement: Measurements accurate to 1/1,000th of an inch (and smaller) Machine Parts Aircraft Components

Measurement Tools Ruler – most common measurement tool – linear dimensions. Protractor – measures angles. Caliper – linear and diameter Micrometer – used to measure linear dimensions. Sliding T-bevel Square – DOES NOT allow for direct angle measurements. Laser – indirect reading (processed by computer). Optical Comparator - indirect reading (processed by computer).

Why Measure? The foundation of a quality control system is measurement and analysis. Measurement is not used to measure just the output of a technology system, but all steps.