Nonelectrical domains

FIGURE 1-2 Data-domain map. The upper (shaded) half of the map consists of nonelectrical domains. The bottom half is made up of electrical domains. Note that the digital domain spans both electrical and nonelectrical domains. 

The determination of the linear dimensions of an object with a rulerand the measurement of the volume of a sample of liquid with a graduated cylinder arc other examples of measurements carried out exclusively in nonelectrical domains. Such measurements are often associated with classical analytical methods. The advent of inexpensive electronic signal processors, sensitive transducers, and readout devices has led to the development of a host of electronic instruments, which acquire information from nonelectrical domains, process it in electrical domains, and linally present it in a nonelectrical way. Electronic devices process information and transform it from one domain to another in ways analogous to the multiplication of mass in mechanical balances with unequal arms. Because these devices are available and capable of rapid and so-... 

Voltmeters, alphanumeric displays, electric motors, computer screens, and many other devices that serve to convert data from electrical to nonelectrical domains are called output transducers. The digital voltmeter of the fluorometer of Figure 1 -3 is a rather complex output transducer that converts the voltage K to a number on a liquid-crystal display so that it may be read and interpreted by the user of the instrument. We shall consider the detailed nature of the digital voltmeter and various other electrical circuits and signals in Chapters 2 through 4. 

Ihe measurement process begins and ends in nonelectrical domains. The physical and chemical information that is of interest in a particular experiment resides in these data domains. Among these characteristics arc length, density, chemical composition, intensity of light, pressure, and others listed in the first column ofl abic I-l. 

It is possible to make a measurement by having the information reside entirely in nonelectrical domains. For instance, the determination of the mass of an object using a mechanical equal-arm balance involves a comparison of (he mass of the object, which is placed on one balance pan. with standard masses placed on a second pan. The information representing (he mass of the object in standard units is encoded direcih by (he experimenter, who provides information processing by... 

As shown by the daia-domain map of Figure 1-2, the digital domain spans both electrical and nonelectrical encoding methods, in the example just cited, the nuclear exent.s are accumulated b using an electronic (xmtuer and displayed on a digital readout. When the experimenter reads and interprets the display, the number tiiai represents the measured quantity is once... 

The modes of encoding information as electrical quantities can be subdivided into analog domains, lime domains, and the digital domain, as illustrated in the bottom half of the circular map in Figure 1-2. Note that the digital domain is not only composed of electrical signals but also includes one nonelectrical representation, because numbers presented on any type of display convey digital information. 

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