The word measurement is used to tell us the length,the weight,the temperature,the colour of a change in one of these physical entities of a material. Measurement provides us with means for describing the various physical and chemical parameters of materials in quantitative terms.Measurement is the result of an opinion formed by one or more observers about the relative size or intensity of some physical quantity.The opinion is formed by the observer after comparing the object with a quantity of same kind chosen as a unit, called standard. the result of measurement is expressed by a number representing the ratio of the unknown quantity to the adopted standard. the number gives the value of the measured quantity. to the adopted standard. this number gives the value is 10 times as large as 1 cm; the unit employed in expressing length.
The measurement standard is the physical embodiment of the unit of measurement as well as that of its submultiple value. This places a sizeable responsibility on the observer, he may be an engineer or a technician, to be certain that the standard used by him is accurately known and commonly accepted. Further, the procedure and apparatus employed for obtaining the comparison must be provable,i.e., accuracy can be reproduced any where in the world. This is essential so that measurements obtained by him can be accepted with confidence. For consistence and quantitative comparison of physical parameters, certain standard of mass, length, time, temperature and electrical quantities have been established. These standards are internationally accepted and well preserved under controlled environmental conditions.
The physical quantity or the characteristic condition which is the object of measurement in an instrumentation system is variously termed as measurand, measurement variable , instrumentation variable and process variable. The measurand may be a fundamental quantity (length,mass and time) a derived quantity (speed,velocity,acceleration,power,etc.) or a quality like pressure , temperature etc.
The measurement standard is the physical embodiment of the unit of measurement as well as that of its submultiple value. This places a sizeable responsibility on the observer, he may be an engineer or a technician, to be certain that the standard used by him is accurately known and commonly accepted. Further, the procedure and apparatus employed for obtaining the comparison must be provable,i.e., accuracy can be reproduced any where in the world. This is essential so that measurements obtained by him can be accepted with confidence. For consistence and quantitative comparison of physical parameters, certain standard of mass, length, time, temperature and electrical quantities have been established. These standards are internationally accepted and well preserved under controlled environmental conditions.
The physical quantity or the characteristic condition which is the object of measurement in an instrumentation system is variously termed as measurand, measurement variable , instrumentation variable and process variable. The measurand may be a fundamental quantity (length,mass and time) a derived quantity (speed,velocity,acceleration,power,etc.) or a quality like pressure , temperature etc.
- Pervariables or through variables which can be specified and measured at one point in spece. Examples are force, momentum, current and charge.
- Transvariables or across variables which need two point (usually one point is the reference) to specify or measure them. Examples are displacement, velocity, temperature and voltage.
No comments:
Post a Comment