ABSTRACT
At the end of this chapter, you should be able to:
• recognise the importance of testing and measurements in electric circuits
• understand the advantages of electronic instruments
• understand the operation of a wattmeter
• understand the operation of an oscilloscope for d.c. and a.c. measurements
• calculate periodic time, frequency, peak to peak values from waveforms on an oscilloscope
• understand null methods of measurement for a Wheatstone bridge and d.c. potentiometer
Tests and in designing, evaluating, maintaining electrical circuits and equipment. In order to detect electrical quantities such as current, voltage, resistance or power, it is necessary to transform an electrical quantity or condition into a visible indication. This is done with the aid of instruments (or meters) that indicate the magnitude of quantities either by the position of a pointer moving over a graduated scale (called an analogue instrument) or in the form of a decimal number (called a digital instrument). The digital instrument has, in the main, become the instrument of choice in recent years; in particular, computer-based instruments are rapidly replacing items of conventional test equipment, with the virtual storage test instrument, the digital storage oscilloscope, being the most common.
