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# Metrology Assignment Ppt

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### Metrology Assignment Ppt

1. 1. It is the degree to which the measured value of the quality characteristic agree with the true value. The difference between the true value and the measured value is known as error of measurement.
2. 2. Calibration is the process of establishing the relationship between a measuring device and the units of measure. This is done by comparing a device or the output of an instrument to a standard having known measurement characteristics.
3. 3. Calibration is the process of configuring an instrument to provide a result for a sample within an acceptable range. Eliminating or minimizing factors that cause inaccurate measurements is a fundamental aspect of instrumentation design. The results are used to establish a relationship between the measurement technique used by the instrument and the known values. The instrument can then provide more accurate results when samples of unknown values are tested in the normal usage of the product.
4. 4. A YARD is a unit of length in several different systems, including English units, Imperial units, and United States customary units. It is equal to 3 feet or 36 inches, although its length in SI units varied slightly from system to system. The most commonly used yard today is the international yard, which is equal to precisely 0.9144 meter.
5. 5. The meter is the length of the path travelled by light in vacuum during a time interval of 1/299 792 458 of a second. International Prototype meter is defined as the straight line distance, at 0’c between the engraved lines of a platinum iridium alloy of 1020 mm of total length and having a cross-section as shown in the figure. The graduations are on the upper surface of the web, which coincides with the neutral axis of the section. The sectional shape gives better rigidity for the amount of metal involved and is therefore economic in use for an expensive metal.
6. 6. The metre or meter is the basic unit of length in the International System of Units (SI). The metre was defined by the French Academy of Sciences as the length between two marks on a platinum-iridium bar, which was designed to represent one ten-millionth of the distance from the Equator to the North Pole through Paris. In 1983, the metre was redefined as the distance travelled by light in free space in 1⁄299,792,458 of a second.
7. 7. Scale can be accurately embalmed, but the engraved lines posses thickness and it is not possible to accurately measure. Scale is used over a wide range. Scale markings are subjected to wear. However the ends are subjected to wear and this leads to undersize measurements. Scale does not posses built in datum. Therefore it is not possible to align the scale with the axis of measurement. Scales are subjected to parallax errors. Assistance of magnifying glass or microscope is required.
8. 8. Highly accurate and used for measurement of closed tolerances in precision engineering as well as standard laboratories, tool rooms, inspection departments. They require more time for measurement and measure only one dimension. They wear at their measuring faces They are not subjected to parallax error.
9. 9. Not a material standard and hence it is not influenced by effects of variation of environmental conditions like temperature, pressure It need not be preserved or stored under security and thus there is not fear of being destroyed. It is subjected to destruction by wear and tear. It gives the unit of length which can be produced consistently at all times. The standard facility can be easily available in all standard laboratories and industries Can be used for making comparative measurements of very high accuracy.