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A measuring instrument for lengths: a typical tape measure with both metric and imperial units and two US pennies for comparison A measuring instrument is a device to measure a physical quantity . In the physical sciences , quality assurance , and engineering , measurement is the activity of obtaining and comparing physical quantities of real ...
A protractor is a measuring instrument, typically made of transparent plastic, for measuring angles. Some protractors are simple half-discs or full circles. More advanced protractors, such as the bevel protractor, have one or two swinging arms, which can be used to help measure the angle. Most protractors measure angles in degrees (°). Radian ...
Tools such as pens and pencils mark the drawing medium. Other tools such as straight edges, assist the operator in drawing straight lines, or assist the operator in drawing complicated shapes repeatedly. Various scales and the protractor are used to measure the lengths of lines and angles, allowing accurate scale drawing to be carried out.
Tape measures are often used for measurement of smaller distances. 3D scanners and various forms of aerial imagery are also used. The theodolite is an instrument for the measurement of angles. It uses two separate circles, protractors or alidades to measure angles in the horizontal and the vertical plane. A telescope mounted on trunnions is ...
The sum of the angles equals 90 degrees (22.5° +67.5°= 90°). It is also obvious from a visual check when using a protractor that where the instruments displays 22.5° is actually 67.5° on the protractor. Many newer slide miters and miter boxes display both angles. Some of the new calculators have a 0° and a 90° references.
A Chesterman tape measure. James Chesterman, a British metalworker, is credited with the invention of the first retractable tape measure in 1821. [6] His design consisted of a spring-loaded cloth strip with marked measurements, housed within a compact case. Building upon his prior design, Chesterman would patent the first steel tape measure. [7]