1. Measuring Techniques. Unit 4-2

2. Measuring Techniques The measurement of part and product size is important in technological design and production activities. Generally this type of measurement can be divided into two levels of accuracy, Standard Measurement and Precision measurement.

3. Standard Measurement Many production settings do not require close measurements. The length of a house, the width of a playing field need not be very accurate. If the product is within a fraction of an inch it will work fine. These measurements are often given to the foot, inch or fraction of an inch in the customary system, or the nearest whole millimeter in the metric system.

4. Standard Measurement The material being measured is also important. For example, wood changes (expands or shrinks) in size with changes in moisture content and the atmospheric humidity. Measurements closer than 1/32 in. or 1mm are not useful. Wood can change more than that in one day.

5. Standard measurements Standard measurements are common in cabinet and furniture manufacturing plants, construction industries, and printing companies. The printing industry uses its own system based on the pica (1/6in.) and the point (1/72in.)

6. Precision Measurement Standard measurement is not accurate enough for many production applications. Watch parts and engine pistons would be useless if they varied by as much a 1/32in. (0.8mm). These parts must be manufactured to an accurate size. For this type of production, precision measurement is required. Measurements of 1/1000 in. to 1/10,000 in. are precise in the customary system. Metric precision measurement will measure to within 0.01mm (one one-hundredth of a millimeter).

7. Direct Reading Measurement Tools Three common uses of measurement are finding linear dimensions, diameters, and angles. Each of these three features can be measured using standard precision devices.

8. Linear Measurement The most common linear measurement device is the rule. The most common divisions are sixteenths (1/16 in.) Metric rules are divided in whole millimeters. The part is measured with a rule by aligning one end of the part with the end of the rule or with an inch mark. The linear measurement is taken by reading the rule division at the other end of the part.

10. Flexible rules are often called tape rules. They are used in woodworking and carpentry applications. There is a hook at one end of the rule that is hooked to the end of the board or structure. The tape is pulled out until it reaches the other end of the board or structure. A measurement is then taken. Linear Measurement

11. Measuring Diameters A common measurement task involves determining the diameter of round material or parts. Precise diameters can be measured by placing a part between the anvil and the spindle of a micrometer and reading the measurement on the barrel.

12. Measuring Angles The angle between two adjacent surfaces is important in many situations. The legs of a desk are generally square (at a 90  angle) with the top. Squares are used to mark angles. The head is placed against one surface of the material. The blade is allowed to rest on an adjacent surface. If the blade touches the surface over its entire length, the part is square.

13. Indirect Reading Measurement Tools In many modern measuring systems, humans no longer take measurements. Sensors gather the measurement data, which is processed by computers or other automatic devices. The final measurement can be displayed on an output device such as a digital read-out, computer screen, or printout. These new systems include laser measuring devices, optical comparators, and direct reading thermometers.

14. Measurement is necessary in designing most anything. Its size, shape, or other properties are communicated through measurements. Processing equipment is set up and operated using these design measurements. Materials needed to construct the item are ordered using measurement systems. All personal or industrial production is based on measurement systems.

15. Measurement can also be used to compare the present condition with a desired condition. The process of setting standards, measuring features, comparing them to standards, and making corrective actions is called quality control. The foundation of a quality control system is measurement and analysis.

16. Summary Measurement describes distance, mass, time, temperature, number of particles, electrical current, and light intensity. It involves comparing a physical characteristic to an established standard. The common standards are the metric system and the U.S. customary system. These systems allow people to communicate designs, order materials, set up machines, fabricate products, and control quality.