Page 801 - Basic Electrical Engineering

11

Measurement and Measuring Instruments

TOPICS DISCUSSED

Concept of measurement and measuring systems
Analog and digital instruments
Static and dynamic characteristics of instruments
Classification of instruments
Measurement error
Permanent magnet moving-coil, moving-iron, and dynamometer-type instruments
Extension of instrument range
Measurement of power
Measurement of energy
Instrument transformers
Megger and multimeter

11.1 INTRODUCTION

Measurement of any quantity, like length, mass, time, speed, velocity,
pressure, temperature, current, voltage, power, etc., is nothing but
comparison of the quantity against some standards. As for example, when we

measure the length of a piece of cloth with a meter scale, we only compare a
particular length against the standard calibrated scale. Using a meter scale to

measure the length of a piece of cloth is the direct method of measurement. In
engineering applications, for measurement of a variable quantity like

pressure, velocity, temperature, etc., indirect methods are used. In on indirect
method, a sensing element called transducer converts the quantity to be