FIGURE 6.1 The electromagnetic radiation spectrum covers everything from very low frequency (VLF)...

FIGURE 6.1 The electromagnetic radiation spectrum covers everything from very low frequency (VLF) radio to X-rays and beyond.

Curtis JohnsonProcess Control Instrumentation Technology, 8e]

Copyright ©2006 by Pearson Education, Inc.Upper Saddle River, New Jersey 07458

All rights reserved.

FIGURE 6.2 The energy carried by one photon varies inversely with the wavelength of the EM radiation.




FIGURE 6.3 Sources of EM radiation exhibit divergence through the spreading of the beam with distance from the source.




FIGURE 6.4 Diagram to aid in solving divergence problems, as in Example 6.5.




FIGURE 6.5 The intensity of light from a point source depends on the distance from the source, R, and the area considered, A.




FIGURE 6.6 Comparison of EM radiation emitted by the sun and heated tungsten filament, as well as the spectral sensitivity of the human eye.




FIGURE 6.7 The candela is defined in terms of uniform monochromatic radiation from a point source.




FIGURE 6.8 The photoconductive cell has a structure to maximize exposure and minimize resistance.




FIGURE 6.8 (continued) The photoconductive cell has a structure to maximize exposure and minimize resistance.




FIGURE 6.9 A photoconductive cell resistance changes nonlinearly with radiation intensity.




FIGURE 6.10 This circuit is the solution for Example 6.7.




FIGURE 6.11 A photovoltaic “solar” cell is a giant pn junction diode.




FIGURE 6.12 The IV curves of a pn junction diode vary with exposure to EM radiation.




FIGURE 6.13 The Thévenin equivalent circuit for a photovoltaic cell. The resistance also varies with radiation.




FIGURE 6.14 This circuit converts the cell short-circuit current into a proportional voltage.




FIGURE 6.15 One solution to Example 6.8.




FIGURE 6.16 The photodiode uses the pn junction reverse current to measure radiation.




FIGURE 6.17 Photodiodes are very small and often use an internal lens to focus light on the junction.




FIGURE 6.18 Circuit for Example 6.9.




FIGURE 6.19 A phototransistor does not need base current because it is effectively supplied by incoming light intensity.




FIGURE 6.20 IV curves of phototransistor collector current and collector-emitter voltage form a family of curves with light intensity as the parameter.




FIGURE 6.21 Structure of the basic photoemissive diode.




FIGURE 6.22 A photomultiplier depends on multiplication of photoelectrons to achieve a high gain. Each dynode is maintained at successively more positive voltages to accelerate the electrons.




FIGURE 6.23 Ideal curves of EM radiation as a function of temperature.




FIGURE 6.24 A blackbody can be simulated by a hole in a metal sphere at a temperature, T.




FIGURE 6.25 A total radiation pyrometer determines an object’s temperature by input of radiation of a broad band of wavelengths.




FIGURE 6.26 An optical pyrometer matches the intensity of the object to a heated, calibrated filament. Comparison is made in the red, using red filters.




FIGURE 6.27 Examples of the appearance of the filament during use of an optical pyrometer.




FIGURE 6.28 A representation of electron transitions in an atom with the emission of EM radiation.




FIGURE 6.29 An energy-level diagram schematically shows the electron orbit energies and possible transitions.




FIGURE 6.30 Stimulated emission of radiation gives rise to monochromatic, coherent radiation pulses moving in random directions.




FIGURE 6.31 A laser gives preference to radiation pulses emitted perpendicular to reflecting surfaces.




FIGURE 6.32 Label-inspection system as an example of optical technique.




FIGURE 6.33 One possible circuit to implement Example 6.12.




FIGURE 6.34 Turbidity measurement can be made in-line with this optical system.




FIGURE 6.35 Circuit for Problem 6.13.




FIGURE 6.36 Circuit for Problem 6.16.




FIGURE 6.37 Figure for Problem 6.22.




FIGURE 6.38 Setup for Problem S6.1.




FIGURE 6.39 Solar tracking system.




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FIGURE 6.1 The electromagnetic radiation spectrum covers everything from very low frequency (VLF)...

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