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Concepts for describing aspects of nature by numbers are called physical quantities. Examples may range from counting fruit to reading a thermometer gauge to determine temperature. Acquiring such a number, a set of such numbers or related numbers directly from a natural system is called measurement. Examples include counting fruit or using a ruler to measure length. Often the concepts or ideas that define physical quantities offer themselves straightforward (time, length, ...). To directly assess the value or number of a physical quantity usually proves difficult when very small or very large values are to be measured or when one intends to obtain a high precision measurement. Again examples indicate actual proceedings: In practice, larger amounts of fruit won't be counted but sold by weight. Distances between villages may be measured by counting the rotations of a Surveyor's wheel. Thus this instrument has to be gauged to yield the proper number indicating the distance with respect to some reference. Furthermore, there may exist innate properties of the natural phenomena that require special attention: Within the thermodynamics-related view on nature, the measurement of entropy could produce entropy itself. Measurements in domains of quantum theory are said to influence the measured quantity significantly. Skilled devising of measurement methods and measurement instruments allows to circumvent these problems and nevertheless acquire useful data. A measuring principle condenses the essentials of a method or an instrument for gaining the desired numbers. ==Counting integers== An elementary measurement method. Used by humans without any device. And realized by mechanical and electronic automatons. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Measuring principle」の詳細全文を読む スポンサード リンク
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