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FIGURE 4.1 Energy bands for solids. Only conduction-band electrons are free to carry current. Curtis Johnson Process Control Instrumentation Technology,

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Presentation on theme: "FIGURE 4.1 Energy bands for solids. Only conduction-band electrons are free to carry current. Curtis Johnson Process Control Instrumentation Technology,"— Presentation transcript:

1 FIGURE 4.1 Energy bands for solids. Only conduction-band electrons are free to carry current. Curtis Johnson Process Control Instrumentation Technology, 8e] Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey All rights reserved.

2 FIGURE 4.2 Metal resistance increases almost linearly with temperature. Curtis Johnson Process Control Instrumentation Technology, 8e] Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey All rights reserved.

3 FIGURE 4.3 Line L represents a linear approximation of resistance versus temperature between T 1 and T 2. Curtis Johnson Process Control Instrumentation Technology, 8e] Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey All rights reserved.

4 FIGURE 4.4 Note the compensation lines in this typical RTD signal-conditioning circuit. Curtis Johnson Process Control Instrumentation Technology, 8e] Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey All rights reserved.

5 FIGURE 4.5 Thermistor resistance versus temperature is highly nonlinear and usually has a negativeslope. Curtis Johnson Process Control Instrumentation Technology, 8e] Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey All rights reserved.

6 FIGURE 4.6 Divider circuit for Example 4.8. Curtis Johnson Process Control Instrumentation Technology, 8e] Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey All rights reserved.

7 FIGURE 4.7 The Seebeck and Peltier effects refer to the relation between emf and temperature in a two-wire system. Curtis Johnson Process Control Instrumentation Technology, 8e] Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey All rights reserved.

8 FIGURE 4.8 Practical measurements with a thermocouple system often employ extension wires to move the reference to a more secure location. Curtis Johnson Process Control Instrumentation Technology, 8e] Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey All rights reserved.

9 FIGURE 4.9 These curves of thermocouple voltage versus temperature for a reference show the different sensitivities and nonlinearities of three types. Curtis Johnson Process Control Instrumentation Technology, 8e] Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey All rights reserved.

10 FIGURE 4.10 A change of reference from 0 ° C to 20 ° C is equivalent to sliding the TC curve down in voltage. Curtis Johnson Process Control Instrumentation Technology, 8e] Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey All rights reserved.

11 FIGURE 4.11 Automatic reference correction is now common in TC systems. Frequently thermistors or other solid-state temperature sensors are used for the reference measurement. Curtis Johnson Process Control Instrumentation Technology, 8e] Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey All rights reserved.

12 FIGURE 4.12 Since TC voltages are small, great care must be taken to protect against electrical noise by using shielding, twisting, and differential amplification. Curtis Johnson Process Control Instrumentation Technology, 8e] Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey All rights reserved.

13 FIGURE 4.13 A solid object experiences a physical expansion in proportion to temperature. Here the effect is highly exaggerated. Curtis Johnson Process Control Instrumentation Technology, 8e] Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey All rights reserved.

14 FIGURE 4.14 A bimetal strip will curve when exposed to a temperature change because of different thermal expansion coefficients. Metal thickness has been exaggerated in this view. Curtis Johnson Process Control Instrumentation Technology, 8e] Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey All rights reserved.

15 FIGURE 4.15 Vapor-pressure curve for methyl chloride. Curtis Johnson Process Control Instrumentation Technology, 8e] Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey All rights reserved.

16 FIGURE 4.16 Some solid-state temperature sensors operate like a zener diode whose voltage depends upon temperature. Curtis Johnson Process Control Instrumentation Technology, 8e] Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey All rights reserved.

17 FIGURE 4.17 One possible solution to Example Curtis Johnson Process Control Instrumentation Technology, 8e] Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey All rights reserved.

18 FIGURE 4.18 Circuit solution for Example Trimmer resistors are used to obtain nonstandard resistance values. Curtis Johnson Process Control Instrumentation Technology, 8e] Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey All rights reserved.

19 FIGURE 4.19 Vapor temperature-control process for Example Curtis Johnson Process Control Instrumentation Technology, 8e] Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey All rights reserved.

20 FIGURE 4.20 One possible solution for Example Curtis Johnson Process Control Instrumentation Technology, 8e] Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey All rights reserved.

21 FIGURE 4.21 One possible solution for Example Curtis Johnson Process Control Instrumentation Technology, 8e] Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey All rights reserved.

22 FIGURE 4.22 Circuit for Problem Curtis Johnson Process Control Instrumentation Technology, 8e] Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey All rights reserved.

23 FIGURE 4.23 Electrical power from a lantern flame using thermocouples. See Problem S4.1. Curtis Johnson Process Control Instrumentation Technology, 8e] Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey All rights reserved.

24 FIGURE 4.24 Use of thermistors for measurement of wind speed in Problem S4.3. Curtis Johnson Process Control Instrumentation Technology, 8e] Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey All rights reserved.


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