Metrology

• Industrial Metrology is the application of measurement science to manufacturing and other processes and their use in the society.
• Inspection in engineering activities involves the measurements, tests, and gauges applied to certain characteristics in regard to an object or activity.
• A Standard is an exact quantity that people agree to use for comparison.
• Primary Standards are the material standard preserved under most careful conditions and are not used for directly for measurements but are used once in 10 or 20 years of calibrating secondary standards.
• Secondary Standards have a value that is less accurate than primary standard and it is obtained by comparing with primary standard.
• Tertiary Standards exist as the ultimate controls for reference at rate intervals and are maintained in National Physics Laboratories (NPL).
• Working Standards are similar in design to primary, secondary & tertiary standards but are less in cost and are made of low grade materials and are used for general application of metrology laboratories.
• Line Standards are the standard in which the distance is measured between two straight and parallel lines.
• End Standards are when the distance is measured between two flat and parallel surfaces.
• Wavelength Standards are materials standards subjected to errors due to continuous use.
• Slip Gauges are rectangular blocks of steel having a cross section about 30x10mm.
• Selecting Slips is the minimum number of slip gauges chosen for combination of blocks depending on the type of set available.
• Accuracy is the closeness of measured value with true value.
• Precision is defined as repeatability of measuring instruments, how close the measured values are to each other.
• Sensitivity is the ratio of change in output of an instrument to smallest change in input.
• Hysteresis is the difference between the indications of measuring instrument when the same value of the measured quantity is reached by increasing or by decreasing that quantity.
• Repeatability, also known as test-retest, is the variation in measurements taken by a single person or instrument on the same item, under the same conditions and in a short period of time.
• Reproducibility is a quantitative measurement of the closeness of the agreement.
• Calibration is the process through which the reliability of instrument is maintained by comparing the instrument with known standards.
• Drift is an instrument’s ability to maintain its calibration over a period of time.
• Range is expressed by stating upper and lower values.
• Resolution is the ability of instrument which can read smallest dimensions of measurement.
• Systematic Errors in experimental observations usually come from the measuring instruments and are controllable in nature.
• Combination Set is the most commonly used in layout inspection purpose.
• Cubit was the measurement used by the Egyptians to build the pyramids.
• Cubit is the measure from your elbow to the tip of your middle finger when your arm is extended.
• Fathom was used by seamen to measure the depth of water so that boats would not run aground and be stranded.
• Fathom is the measure from fingertip to fingertip when your arms are stretched sideways as far as they will go.
• Hand-span was used to measure the height of horses.
• Hand-span It is the measure from the tip of your pinky to the tip of your thumb when your hand is stretched out.
• Hand-span is the measure from the tip of your pinky to the tip of your thumb when your hand is stretched out.
• Pace was a term used by the Roman army to judge speed.
• Pace is still used frequently during various types of foot races.
• Pace is the measure of distance from one step to another.
• Foot is a measurement equal to the length of an individuals foot.
• King Henry 1 standardized this measurement, because his foot was 12 inches long.
• Girth was a measurement often used to measure fishing line.
• Girth was the measurement around one’s stomach (your belt measure).
• Palm is the width of your four fingers when they are placed together.
• The Mars Climate Orbiter, a key craft in the space agency’s exploration of the red planet, vanished after a rocket firing September 23 that was supposed to put the spacecraft on orbit around mars.