Overview

Electronic test instruments are important tools for the design, development, manufacture, calibration, and repair of electronic circuits and equipment. The ancestors of today's instruments were invented by physicists and electrical engineers well before the start of the electronics era, and they proved to be essential in the development of the telegraph, the telephone, motors, and electrical power generators. The classical test instruments include the Wheatstone bridge and the many moving-coil meters descended from the galvanometer the voltmeter, ammeter, ohmmeter, and wattmeter. These instruments were themselves the predecessors of the analog multimeter or volt-ohm milliammeter (VOM), the multipurpose instrument that made bench and field testing convenient and affordable.

The analog multimeter has since been replaced by the digital multimeter (DMM), now the multipurpose test instrument of choice. In addition to being able to measure the five basic electrical variables, it has consolidated a benchful of other instruments in a single case. DMMs can also measure capacitance, temperature, frequency, electrical continuity, and can even evaluate diodes and transistors.

These capabilities were made possible by the introduction of the monolithic analog-to-digital converter IC, the liquid-crystal display, and the decoder/driver IC. The convenience of being able to read a measurement directly from a meter instead of having to estimate its value by interpolating a pointer position made routine testing easier, faster, and more accurate. However, the analog "moving bar" display on meters has been preserved on digital instruments because it indicates trends and transients in real time.

The oscilloscope is another classical electronic test...