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UNITS AND DIMENSIONS

METHODS OF MEASUREMENTS AND MEASURING INSTRUMENTS

Requirements of Instruments

Classification of Instruments

Accuracy and Precision

Resolution and Overshoot

REVIEW OF FUNDAMENTAL AND DERIVED UNITS

DIMENSIONAL ANALYSIS

SOLVED PROBLEMS

MEASUREMENT OF RESISTANCES

CLASSIFICATION OF RESISTANCES

MEASUREMENT OF MEDIUM RESISTANCES

MEASUREMENT OF LOW RESISTANCES

SOLVED PROBLEMS2

UNITS AND DIMENSIONS

ART OF MEASUREMENTS

Measurement of a quantity is the result of a comparison between the unknown quantity and its predefined standard. A measuring system is required to quantify the parameters involved and establish clear rules about their relative values. Early systems of measurements were based on imprecise units, while the modern measurement systems are based on accurately defined units. Many standard measuring units have been established at different levels of measurements. The significance of electrical measurements and measuring instruments is evident from the rapid developments in the field of electrical engineering owing to the developments in their measuring devices. The measurement is meaningful only if the standards are accurately defined, reliable and commonly accepted, the methods used are well proven and the circuit conditions are little
affected by the introduction of the measuring systems. The parameter under measurement is referred as measurand and it is always measured in terms of its numeric value. The process of measurement through a meter is referred as Instrumentation. Electrical measuring instruments are the most common devices used not only for the measurement of electrical quantities, but also for all other quantities, which could be transformed into an electrical signal. The usual quantities to be measured are current, voltage, power, energy,
frequency, power factor, etc. The various circuit parameters also need to be measured such as resistance, inductance, capacitance, etc. An umpteen number and varieties of measuring instruments have been developed for measurement purposes. In other words, measurement and instrumentation are based on different methods depending upon the characteristic features of the quantity being measured.