FIGURE 6.1 The electromagnetic radiation spectrum covers everything from very low frequency (VLF) radio to X-rays and beyond. Curtis Johnson Process 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. Curtis Johnson Process Control Instrumentation Technology, 8e] Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.

FIGURE 6.3 Sources of EM radiation exhibit divergence through the spreading of the beam with distance from the source. Curtis Johnson Process Control Instrumentation Technology, 8e] Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.

FIGURE 6.4 Diagram to aid in solving divergence problems, as in Example 6.5. Curtis Johnson Process Control Instrumentation Technology, 8e] Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.

FIGURE 6.5 The intensity of light from a point source depends on the distance from the source, R, and the area considered, A. Curtis Johnson Process Control Instrumentation Technology, 8e] Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.

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. Curtis Johnson Process Control Instrumentation Technology, 8e] Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.

FIGURE 6.7 The candela is defined in terms of uniform monochromatic radiation from a point source. Curtis Johnson Process Control Instrumentation Technology, 8e] Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.

FIGURE 6.8 The photoconductive cell has a structure to maximize exposure and minimize resistance. Curtis Johnson Process Control Instrumentation Technology, 8e] Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.

FIGURE 6.8 (continued) The photoconductive cell has a structure to maximize exposure and minimize resistance. Curtis Johnson Process Control Instrumentation Technology, 8e] Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.

FIGURE 6.9 A photoconductive cell resistance changes nonlinearly with radiation intensity. Curtis Johnson Process Control Instrumentation Technology, 8e] Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.

FIGURE 6.10 This circuit is the solution for Example 6.7. Curtis Johnson Process Control Instrumentation Technology, 8e] Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.

FIGURE 6.11 A photovoltaic “solar” cell is a giant pn junction diode. Curtis Johnson Process Control Instrumentation Technology, 8e] Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.

FIGURE 6.12 The IV curves of a pn junction diode vary with exposure to EM radiation. Curtis Johnson Process Control Instrumentation Technology, 8e] Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.

FIGURE 6. 13 The Thévenin equivalent circuit for a photovoltaic cell FIGURE 6.13 The Thévenin equivalent circuit for a photovoltaic cell. The resistance also varies with radiation. Curtis Johnson Process Control Instrumentation Technology, 8e] Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.

FIGURE 6.14 This circuit converts the cell short-circuit current into a proportional voltage. Curtis Johnson Process Control Instrumentation Technology, 8e] Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.

FIGURE 6.15 One solution to Example 6.8. Curtis Johnson Process Control Instrumentation Technology, 8e] Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.

FIGURE 6.16 The photodiode uses the pn junction reverse current to measure radiation. Curtis Johnson Process Control Instrumentation Technology, 8e] Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.

FIGURE 6.17 Photodiodes are very small and often use an internal lens to focus light on the junction. Curtis Johnson Process Control Instrumentation Technology, 8e] Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.

FIGURE 6.18 Circuit for Example 6.9. Curtis Johnson Process Control Instrumentation Technology, 8e] Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.

FIGURE 6.19 A phototransistor does not need base current because it is effectively supplied by incoming light intensity. Curtis Johnson Process Control Instrumentation Technology, 8e] Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.

FIGURE 6.20 IV curves of phototransistor collector current and collector-emitter voltage form a family of curves with light intensity as the parameter. Curtis Johnson Process Control Instrumentation Technology, 8e] Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.

FIGURE 6.21 Structure of the basic photoemissive diode. Curtis Johnson Process Control Instrumentation Technology, 8e] Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.

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. Curtis Johnson Process Control Instrumentation Technology, 8e] Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.

FIGURE 6.23 Ideal curves of EM radiation as a function of temperature. Curtis Johnson Process Control Instrumentation Technology, 8e] Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.

FIGURE 6.24 A blackbody can be simulated by a hole in a metal sphere at a temperature, T. Curtis Johnson Process Control Instrumentation Technology, 8e] Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.

FIGURE 6.25 A total radiation pyrometer determines an object’s temperature by input of radiation of a broad band of wavelengths. Curtis Johnson Process Control Instrumentation Technology, 8e] Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.

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. Curtis Johnson Process Control Instrumentation Technology, 8e] Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.

FIGURE 6.27 Examples of the appearance of the filament during use of an optical pyrometer. Curtis Johnson Process Control Instrumentation Technology, 8e] Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.

FIGURE 6.28 A representation of electron transitions in an atom with the emission of EM radiation. Curtis Johnson Process Control Instrumentation Technology, 8e] Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.

FIGURE 6.29 An energy-level diagram schematically shows the electron orbit energies and possible transitions. Curtis Johnson Process Control Instrumentation Technology, 8e] Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.

FIGURE 6.30 Stimulated emission of radiation gives rise to monochromatic, coherent radiation pulses moving in random directions. Curtis Johnson Process Control Instrumentation Technology, 8e] Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.

FIGURE 6.31 A laser gives preference to radiation pulses emitted perpendicular to reflecting surfaces. Curtis Johnson Process Control Instrumentation Technology, 8e] Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.

FIGURE 6.32 Label-inspection system as an example of optical technique. Curtis Johnson Process Control Instrumentation Technology, 8e] Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.

FIGURE 6.33 One possible circuit to implement Example 6.12. Curtis Johnson Process Control Instrumentation Technology, 8e] Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.

FIGURE 6.34 Turbidity measurement can be made in-line with this optical system. Curtis Johnson Process Control Instrumentation Technology, 8e] Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.

FIGURE 6.35 Circuit for Problem 6.13. Curtis Johnson Process Control Instrumentation Technology, 8e] Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.

FIGURE 6.36 Circuit for Problem 6.16. Curtis Johnson Process Control Instrumentation Technology, 8e] Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.

FIGURE 6.37 Figure for Problem 6.22. Curtis Johnson Process Control Instrumentation Technology, 8e] Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.

FIGURE 6.38 Setup for Problem S6.1. Curtis Johnson Process Control Instrumentation Technology, 8e] Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.

FIGURE 6.39 Solar tracking system. Curtis Johnson Process Control Instrumentation Technology, 8e] Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.