Chapter 7 – Electrical Indicating and Test Instruments

Publisher Summary This chapter examines various ways of measuring electrical signals that form the output of most types of measuring instruments. The oscilloscope is a very versatile measuring instrument widely used for signal measurement, despite the measurement accuracy provided being inferior to that of most meters. Although existing in both analogue and digital forms, most instruments used professionally are now digital, with analogue versions being limited to inexpensive, low-specification instruments intended for use in educational establishments. Digital meters designed to measure quantities other than voltage are, in fact, digital voltmeters that contain appropriate electrical circuits to convert current or resistance measurement signals into voltage signals. Digital multimeters are also essentially digital voltmeters that contain several conversion circuits, thus allowing the measurement of voltage, current, and resistance within one instrument. Despite the technical superiority of digital meters, particularly in terms of their greater accuracy and much higher input impedance, analogue meters continue to be used in a significant number of applications.