TABLE OF CONTENTS To fully understand the specifications for converters it is beneficial to cover the fundamentals of sampling theory.
Analog-to-digital converters (ADCs) translate analog measurements, which are characteristic of most phenomena in the "real world," to digital language, used in information processing, computing, data transmission, and control systems. Digital-to-analog converters (DACs) are used in transforming transmitted or stored data, or the results of digital processing, back to "real-world" variables for control, information display, or further analog processing. The relationships between inputs and outputs of ADCs and DACs are shown in Figure 5-1
Analog input variables, whatever their origin, are most frequently converted by transducers into voltages or currents. These electrical quantities may appear as fast or slow "DC" continuous direct measurements of a phenomenon in the time domain, as modulated AC waveforms (using a wide variety of modulation techniques), or in some combination, with a spatial configuration of related variables to represent shaft angles. Examples of the first are outputs of thermocouples, potentiometers on DC references, and analog computing circuitry; of the second, "chopped" optical measurements, AC strain gauge or bridge outputs, and digital signals buried in noise; and of the third, synchros and resolvers.
The analog variables to be dealt with in this chapter are those involving voltages or currents representing the actual analog phenomena. They may be either wideband or narrowband. They may be either scaled from the direct measurement or subjected to some...
